完结IIO子系统

IMX6ULL/doc_pic/14_IIO/04_iio_event的使用.md

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+# iio_event的使用
+
+IIO(Industrial I/O)参考资料：
+
+* 系列文章：https://blog.csdn.net/lickylin/article/details/108177756
+* https://www.cnblogs.com/yongleili717/p/10758691.html
+* 内核文档：https://www.kernel.org/doc/html/v5.3/driver-api/iio
+* 参考内核源码
+  * `drivers\staging\iio\impedance-analyzer\ad5933.c`
+  * `drivers\iio\adc\hi8435.c`
+
+
+
+## 1. iio_event的引入与体验
+
+### 1.1 问题引入与解决方法
+
+以温湿度传感器为例，它的温度值超过极限了，APP如何检测到这个事件？
+
+* APP读取某个设备文件
+* 传感器驱动提供数据：
+  * 比如硬件监测到温度超标时，触发硬件中断，在中断里使用iio_push_event把"事件"写入kfifo
+  * APP读取kfifo得到"事件"
+* iio_trigger提供数据：
+  * 有些硬件没有中断引脚，那么可以使用iio_trigger
+  * iio_trigger直接调用驱动程序提供的的另一个"虚拟中断处理函数"(跟iio_buffer不一样的中断处理函数)
+  * 这个中断处理函数读取硬件数据，使用iio_push_event把"事件"写入kfifo
+
+![image-20241125161222685](pic/image-20241125161222685.png)
+
+### 1.2 怎么表示事件
+
+使用结构体"iio_event_data"表示事件：
+
+![image-20241125163136804](pic/image-20241125163136804.png)
+
+
+
+所谓事件就是一个64位的ID，里面不含有具体的数值：比如它表示温度超高了，但是没有表示温度值是多少。
+
+这个ID如何表示不同的事件呢？如下：
+
+![image-20241125163406036](pic/image-20241125163406036.png)
+
+
+
+示例：
+
+![image-20241125164423639](pic/image-20241125164423639.png)
+
+
+
+### 1.3 上机体验
+
+IMX6ULL的源码：
+
+![image-20241126094637080](pic/image-20241126094637080.png)
+
+STM32MP157的源码：
+
+![image-20241126094715687](pic/image-20241126094715687.png)
+
+#### 1.3.1 IMX6ULL
+
+```shell
+insmod /root/iio-trig-hrtimer.ko
+mkdir  /sys/kernel/config/iio/triggers/hrtimer/timer_abc  # 创建trigger
+cat /sys/bus/iio/devices/trigger1/name             # 可以看到这个trigger
+
+insmod /root/dht11.ko
+cd /sys/bus/iio/devices/iio\:device2/
+echo timer_abc > trigger/current_trigger               # 在设备上使用trigger
+
+echo 1 > scan_elements/in_humidityrelative_en
+echo 1 > scan_elements/in_temp_en
+echo 1 > buffer/enable
+
+# hexdump /dev/iio\:device2
+/root/dht11_test /dev/iio\:device2  # 读取事件
+```
+
+
+
+#### 1.3.2 STM32MP157
+
+```SHELL
+# insmod /root/iio-trig-hrtimer.ko # 157上已经有了这个驱动
+mkdir  /sys/kernel/config/iio/triggers/hrtimer/timer_abc  # 创建trigger
+cat /sys/bus/iio/devices/trigger1/name             # 可以看到这个trigger
+
+insmod /root/dht11.ko
+cd /sys/bus/iio/devices/iio\:device1/
+echo timer_abc > trigger/current_trigger               # 在设备上使用trigger
+
+echo 1 > scan_elements/in_humidityrelative_en
+echo 1 > scan_elements/in_temp_en
+echo 1 > buffer/enable
+
+# hexdump /dev/iio\:device1
+/root/dht11_test /dev/iio\:device1  # 读取事件
+```
+
+
+
+
+
+## 2. iio_event数据流程
+
+### 2.1 驱动程序创建KFIFO
+
+![image-20241125175311198](pic/image-20241125175311198.png)
+
+
+
+### 2.2 驱动程序写KFIFO
+
+![image-20241125175658789](pic/image-20241125175658789.png)
+
+
+
+### 2.3 APP读取KFIFO
+
+示例源码如下：
+
+```c
+int event_fd;
+struct iio_event_data event;
+
+int fd = open("/dev/iio:device2", O_RDWR);
+
+ioctl(fd, IIO_GET_EVENT_FD_IOCTL, &event_fd);
+read(event_fd, &event, sizeof(event));
+```
+
+
+
+## 3. 修改DHT11驱动使用iio_event
+
+IMX6ULL的源码：
+
+![image-20241127102844284](pic/image-20241127102844284.png)
+
+STM32MP157的源码：
+
+![image-20241127102920957](pic/image-20241127102920957.png)
+
+### 3.1 设备表明自己有event能力
+
+在注册iio设备时，会进行如下判断：
+
+![image-20241125193456857](pic/image-20241125193456857.png)
+
+只有设置了indio_dev->info->event_attrs或某个通道的num_event_specs不为0，才会创建KFIFO。
+
+
+
+示例代码如下：
+
+![image-20241125170901645](pic/image-20241125170901645.png)
+
+
+
+这会生成如下sysfs文件：
+
+![image-20241125170929132](pic/image-20241125170929132.png)
+
+
+
+生成sysfs文件的流程为：
+
+```c
+iio_device_register
+	iio_device_register_eventset
+    	__iio_add_event_config_attrs
+            for (j = 0; j < indio_dev->num_channels; j++) {
+                ret = iio_device_add_event_sysfs(indio_dev,
+                                 &indio_dev->channels[j]);
+							iio_device_add_event                                	
+```
+
+
+
+这些sysfs对应的读写函数如下：
+
+![image-20241125171144376](pic/image-20241125171144376.png)
+
+
+
+### 3.2 设备驱动提供sysfs接口函数
+
+比如我们想指定温度的报警值，那么就需要实现这些sysfs的接口函数：
+
+![image-20241125193714139](pic/image-20241125193714139.png)
+
+
+
+### 3.3 上机实验
+
+#### 1.3.1 IMX6ULL
+
+```shell
+insmod /root/iio-trig-hrtimer.ko
+mkdir  /sys/kernel/config/iio/triggers/hrtimer/timer_abc  # 创建trigger
+cat /sys/bus/iio/devices/trigger1/name             # 可以看到这个trigger
+
+insmod /root/dht11.ko
+cd /sys/bus/iio/devices/iio\:device2/
+echo timer_abc > trigger/current_trigger               # 在设备上使用trigger
+
+echo 30 > events/in_temp_thresh_rising_value   # 设置上限报警值
+echo 10 > events/in_temp_thresh_falling_value  # 设置下限报警值
+echo 1 > events/in_temp_thresh_either_en       # 使能event
+
+echo 1 > scan_elements/in_humidityrelative_en
+echo 1 > scan_elements/in_temp_en
+echo 1 > buffer/enable
+
+# hexdump /dev/iio\:device2
+/root/dht11_test /dev/iio\:device2  # 读取事件
+```
+
+
+
+#### 1.3.2 STM32MP157
+
+```SHELL
+# insmod /root/iio-trig-hrtimer.ko # 157上已经有了这个驱动
+mkdir  /sys/kernel/config/iio/triggers/hrtimer/timer_abc  # 创建trigger
+cat /sys/bus/iio/devices/trigger1/name             # 可以看到这个trigger
+
+insmod /root/dht11.ko
+cd /sys/bus/iio/devices/iio\:device1/
+echo timer_abc > trigger/current_trigger               # 在设备上使用trigger
+
+echo 30 > events/in_temp_thresh_rising_value   # 设置上限报警值
+echo 10 > events/in_temp_thresh_falling_value  # 设置下限报警值
+echo 1 > events/in_temp_thresh_either_en       # 使能event
+
+echo 1 > scan_elements/in_humidityrelative_en
+echo 1 > scan_elements/in_temp_en
+echo 1 > buffer/enable
+
+# hexdump /dev/iio\:device1
+/root/dht11_test /dev/iio\:device1  # 读取事件
+```
+
+
+
+## 4. 使用trigger写iio_event(不实用)
+
+IMX6ULL的源码：
+
+![image-20241126094637080](pic/image-20241126094637080.png)
+
+STM32MP157的源码：
+
+![image-20241126094715687](pic/image-20241126094715687.png)
+
+### 4.1 框图
+
+下图中，左侧写kfifo的红色线条，就是使用trigger写iio_event：
+
+![image-20241125161222685](pic/image-20241125161222685.png)
+
+
+
+### 4.2 提供虚拟中断处理函数
+
+![image-20241127103153056](pic/image-20241127103153056.png)
+
+
+
+### 4.3 注册虚拟中断处理函数
+
+设置iio_device的trgger，比如如下操作：
+
+```shell
+insmod /root/iio-trig-hrtimer.ko
+mkdir  /sys/kernel/config/iio/triggers/hrtimer/timer_abc  # 创建trigger
+cat /sys/bus/iio/devices/trigger1/name             # 可以看到这个trigger
+
+insmod /root/dht11.ko
+cd /sys/bus/iio/devices/iio\:device2/
+echo timer_abc > trigger/current_trigger               # 在设备上使用trigger
+```
+
+会导致如下函数被调用，它就注册了"记录在pollfunc_event里的"虚拟中断函数：
+
+![image-20241127103523330](pic/image-20241127103523330.png)
+
+
+
+注意，对比一下：
+
+* "记录在pollfunc_event里的"虚拟中断函数：
+  * 在设置iio设备的current_trigger时就注册了中断, 就会使能trigger state
+  * 用来产生iio_event，写KFIFO
+* "记录在pollfunc里的"虚拟中断函数：
+  * 在设置iio设备的current_trigger后、并且使能了buffer，才注册中断, 就会使能trigger state
+  * 用来读取传感器数据，写iio_buffer
+
+### 4.4 上机体验
+
+#### 4.4.1 修改内核支持
+
+![image-20241127104547343](pic/image-20241127104547343.png)
+
+
+
+#### 4.4.2 具体操作
+
+IMX6ULL:
+
+```shell
+insmod /root/iio-trig-hrtimer.ko
+mkdir  /sys/kernel/config/iio/triggers/hrtimer/timer_abc  # 创建trigger
+cat /sys/bus/iio/devices/trigger1/name             # 可以看到这个trigger
+
+insmod /root/industrialio-triggered-event.ko
+
+insmod /root/dht11.ko
+cd /sys/bus/iio/devices/iio\:device2/
+echo timer_abc > trigger/current_trigger               # 在设备上使用trigger
+
+echo 30 > events/in_temp_thresh_rising_value   # 设置上限报警值
+echo 10 > events/in_temp_thresh_falling_value  # 设置下限报警值
+echo 1 > events/in_temp_thresh_either_en       # 使能event
+
+echo 1 > scan_elements/in_humidityrelative_en
+echo 1 > scan_elements/in_temp_en
+echo 1 > buffer/enable
+
+# hexdump /dev/iio\:device2
+/root/dht11_test /dev/iio\:device2  # 读取事件
+```
+
+
+
+STM32MP157:
+
+```shell
+# insmod /root/iio-trig-hrtimer.ko # 157上已经有了这个驱动
+mkdir  /sys/kernel/config/iio/triggers/hrtimer/timer_abc  # 创建trigger
+cat /sys/bus/iio/devices/trigger1/name             # 可以看到这个trigger
+
+insmod /root/industrialio-triggered-event.ko
+
+insmod /root/dht11.ko
+cd /sys/bus/iio/devices/iio\:device1/
+echo timer_abc > trigger/current_trigger               # 在设备上使用trigger
+
+echo 30 > events/in_temp_thresh_rising_value   # 设置上限报警值
+echo 10 > events/in_temp_thresh_falling_value  # 设置下限报警值
+echo 1 > events/in_temp_thresh_either_en       # 使能event
+
+echo 1 > scan_elements/in_humidityrelative_en
+echo 1 > scan_elements/in_temp_en
+echo 1 > buffer/enable
+
+# hexdump /dev/iio\:device1
+/root/dht11_test /dev/iio\:device1  # 读取事件
+```
+

IMX6ULL/doc_pic/14_IIO/05_iio驱动示例.md

@@ -0,0 +1,217 @@
+# iio驱动示例
+
+IIO(Industrial I/O)参考资料：
+
+* 系列文章：https://blog.csdn.net/lickylin/article/details/108177756
+* https://www.cnblogs.com/yongleili717/p/10758691.html
+* 内核文档：https://www.kernel.org/doc/html/v5.3/driver-api/iio
+* 参考内核源码
+  * IMX6ULL: `drivers\iio\adc\vf610_adc.c`
+  * STM32MP157: `drivers\iio\adc\stm32-adc-core.c`，`drivers\iio\adc\stm32-adc.c`
+
+
+
+## 1. IMX6ULL ADC驱动
+
+### 1.1 设备树
+
+![image-20241127131900125](pic/image-20241127131900125.png)
+
+
+
+### 1.2 驱动程序
+
+![image-20241127132025400](pic/image-20241127132025400.png)
+
+
+
+### 1.3 驱动程序分析
+
+```shell
+static int vf610_read_raw(struct iio_dev *indio_dev,
+			struct iio_chan_spec const *chan,
+			int *val,
+			int *val2,
+			long mask)
+
+怎么使用val, val2 ?
+
+IIO_VAL_INT : 只有整数没有小数, 整数保存在val里，val2不使用。
+IIO_VAL_INT_PLUS_MICRO : val=整数，val2=小数部分*1000000，比如3.14如此保存：*val = 3; *val2 = 140000
+IIO_VAL_INT_PLUS_NANO  : val=整数，val2=小数部分*1000000000，比如3.14如此保存：*val = 3; *val2 = 140000000
+IIO_VAL_INT_PLUS_MICRO_DB : DB数据，数值的表示方法跟IIO_VAL_INT_PLUS_MICRO一样，添加了单位DB。
+IIO_VAL_INT_MULTIPLE : 返回多个整数值，主要用于iio_info的read_raw_multi函数。
+IIO_VAL_FRACTIONAL   : 分数，比如n/m，表示为：*val=n, *val2=m
+IIO_VAL_FRACTIONAL_LOG2 : LOG2值, 比如*val=1，*val2=4，表示的数值为：val>>val2, 即1>>4=0.03125
+```
+
+
+
+### 1.4 驱动程序使用
+
+#### 1.4.1 各类值的含义
+
+![image-20241127132345881](pic/image-20241127132345881.png)
+
+#### 1.4.2 示例
+
+IMX6ULL原理图：
+
+![image-20241127132457129](pic/image-20241127132457129.png)
+
+可以通过扩展板引出，原理图如下：
+
+![image-20241127132553738](pic/image-20241127132553738.png)
+
+
+
+测试时接线方法：可以把ADC1_CH3或ADC1_CH4，接到3V3或GND，如下图：
+
+![image-20241127145118931](pic/image-20241127145118931.png)
+
+
+
+操作命令：
+
+```shell
+# 单步操作
+cd /sys/bus/iio/devices/iio:device0  
+cat in_voltage3_raw
+
+# 使用buffer
+insmod /root/iio-trig-hrtimer.ko
+mkdir  /sys/kernel/config/iio/triggers/hrtimer/timer_abc  # 创建trigger
+cat /sys/bus/iio/devices/trigger1/name             # 可以看到这个trigger
+# 设置trigger周期
+cd /sys/bus/iio/devices/trigger1
+echo 1000000000 > sampling_frequency  # 单位ns, 1s一次
+
+cd /sys/bus/iio/devices/iio\:device0/
+echo timer_abc > trigger/current_trigger               # 在设备上使用trigger
+
+echo 1 > scan_elements/in_voltage3_en
+echo 1024 > buffer/length
+echo 1 > buffer/enable
+
+# hexdump /dev/iio\:device1
+hexdump /dev/iio\:device0  # 读取数据
+```
+
+
+
+注意：使用buffer功能会死机，原因未明。
+
+
+
+
+
+## 2. STM32MP157 ADC驱动
+
+### 2.1 设备树与驱动
+
+如何确定设备树与驱动？百问网STM32MP157开发板使用的设备树文件是`stm32mp157c-100ask-512d-lcd-v1.dtb`，可以在Ubuntu使用如下命令反汇编得到dts文件：
+
+```shell
+dtc -I dtb -O dts stm32mp157c-100ask-512d-lcd-v1.dtb > 1.dts
+```
+
+在1.dts中搜`adc`，可以看到如下节点，根据里面的`compatible`属性即可找到设备树和驱动：
+
+![image-20241128095523369](pic/image-20241128095523369.png)
+
+
+
+#### 2.1.1 设备树文件
+
+![image-20241128095902459](pic/image-20241128095902459.png)
+
+#### 2.1.2 驱动文件
+
+`drivers\iio\adc\stm32-adc-core.c`，`drivers\iio\adc\stm32-adc.c`
+
+
+
+### 2.2 为何驱动程序无法使用
+
+#### 2.2.1 pinmux空缺
+
+查看内核打印信息：
+
+```shell
+[    4.112842] stm32mp157-pinctrl soc:pin-controller@50002000: missing pins property in node pins .
+[    4.120360] stm32-adc-core: probe of 48003000.adc failed with error -22
+
+```
+
+根据错误信息"missing pins property in node"，找到驱动：pinctrl/stm32/pinctrl-stm32.c
+
+![image-20241128105620144](pic/image-20241128105620144.png)
+
+在设备树里确实发现ADC使用的pinctrl里没有"pinmux"属性：
+
+![image-20241128105502688](pic/image-20241128105502688.png)
+
+
+
+如此修改：
+
+![image-20241128131324394](pic/image-20241128131324394.png)
+
+
+
+#### 2.2.2 提供regulator
+
+![image-20241128132450046](pic/image-20241128132450046.png)
+
+
+
+### 2.3 上机实验
+
+#### 2.3.1 原理图与接线
+
+STM32MP157原理图：
+
+![image-20241128133548599](pic/image-20241128133548599.png)
+
+扩展板原理图：
+
+![image-20241128133617577](pic/image-20241128133617577.png)
+
+
+
+接线方法：
+
+![image-20241128133856564](pic/image-20241128133856564.png)
+
+
+
+#### 2.3.2 测试命令
+
+```shell
+# 单步操作
+cd /sys/bus/iio/devices/iio:device1  
+cat in_voltage0_raw
+
+# 使用buffer
+# insmod /root/iio-trig-hrtimer.ko  # STM32MMP157无需安装驱动
+mkdir  /sys/kernel/config/iio/triggers/hrtimer/timer_abc  # 创建trigger
+cat /sys/bus/iio/devices/trigger1/name             # 可以看到这个trigger
+# 设置trigger周期
+cd /sys/bus/iio/devices/trigger1
+echo 1000000000 > sampling_frequency  # 单位ns, 1s一次
+
+cd /sys/bus/iio/devices/iio\:device1/
+echo timer_abc > trigger/current_trigger               # 在设备上使用trigger
+
+echo 1 > scan_elements/in_voltage0_en
+echo 1024 > buffer/length
+echo 1 > buffer/enable
+
+# hexdump /dev/iio\:device1
+hexdump /dev/iio\:device1  # 读取数据
+```
+
+
+
+### 2.4 驱动程序分析
+

IMX6ULL/source/14_iio/05_dht11_iio_event/dht11.c

@@ -0,0 +1,683 @@
+/*
+ * DHT11/DHT22 bit banging GPIO driver
+ *
+ * Copyright (c) Harald Geyer <harald@ccbib.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/err.h>
+#include <linux/interrupt.h>
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/printk.h>
+#include <linux/slab.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/sysfs.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/wait.h>
+#include <linux/bitops.h>
+#include <linux/completion.h>
+#include <linux/mutex.h>
+#include <linux/delay.h>
+#include <linux/gpio.h>
+#include <linux/of_gpio.h>
+#include <linux/timekeeping.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/kfifo_buf.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/iio/triggered_buffer.h>
+#include <linux/iio/events.h>
+#include <linux/iio/triggered_event.h>
+
+#define DRIVER_NAME	"dht11"
+
+#define DHT11_DATA_VALID_TIME	2000000000  /* 2s in ns */
+
+#define DHT11_EDGES_PREAMBLE 2
+#define DHT11_BITS_PER_READ 40
+/*
+ * Note that when reading the sensor actually 84 edges are detected, but
+ * since the last edge is not significant, we only store 83:
+ */
+#define DHT11_EDGES_PER_READ (2 * DHT11_BITS_PER_READ + \
+			      DHT11_EDGES_PREAMBLE + 1)
+
+/*
+ * Data transmission timing:
+ * Data bits are encoded as pulse length (high time) on the data line.
+ * 0-bit: 22-30uS -- typically 26uS (AM2302)
+ * 1-bit: 68-75uS -- typically 70uS (AM2302)
+ * The acutal timings also depend on the properties of the cable, with
+ * longer cables typically making pulses shorter.
+ *
+ * Our decoding depends on the time resolution of the system:
+ * timeres > 34uS ... don't know what a 1-tick pulse is
+ * 34uS > timeres > 30uS ... no problem (30kHz and 32kHz clocks)
+ * 30uS > timeres > 23uS ... don't know what a 2-tick pulse is
+ * timeres < 23uS ... no problem
+ *
+ * Luckily clocks in the 33-44kHz range are quite uncommon, so we can
+ * support most systems if the threshold for decoding a pulse as 1-bit
+ * is chosen carefully. If somebody really wants to support clocks around
+ * 40kHz, where this driver is most unreliable, there are two options.
+ * a) select an implementation using busy loop polling on those systems
+ * b) use the checksum to do some probabilistic decoding
+ */
+#define DHT11_START_TRANSMISSION_MIN	18000  /* us */
+#define DHT11_START_TRANSMISSION_MAX	20000  /* us */
+#define DHT11_MIN_TIMERES	34000  /* ns */
+#define DHT11_THRESHOLD		49000  /* ns */
+#define DHT11_AMBIG_LOW		23000  /* ns */
+#define DHT11_AMBIG_HIGH	30000  /* ns */
+
+struct dht11 {
+	struct device			*dev;
+
+	int				gpio;
+	int				irq;
+
+	struct completion		completion;
+	/* The iio sysfs interface doesn't prevent concurrent reads: */
+	struct mutex			lock;
+
+	s64				timestamp;
+	int				temperature;
+	int				humidity;
+
+	/* num_edges: -1 means "no transmission in progress" */
+	int				num_edges;
+	struct {s64 ts; int value; }	edges[DHT11_EDGES_PER_READ];
+	struct delayed_work		work;
+	struct iio_dev *iio;
+};
+
+#ifdef CONFIG_DYNAMIC_DEBUG
+/*
+ * dht11_edges_print: show the data as actually received by the
+ *                    driver.
+ */
+static void dht11_edges_print(struct dht11 *dht11)
+{
+	int i;
+
+	dev_dbg(dht11->dev, "%d edges detected:\n", dht11->num_edges);
+	for (i = 1; i < dht11->num_edges; ++i) {
+		dev_dbg(dht11->dev, "%d: %lld ns %s\n", i,
+			dht11->edges[i].ts - dht11->edges[i - 1].ts,
+			dht11->edges[i - 1].value ? "high" : "low");
+	}
+}
+#endif /* CONFIG_DYNAMIC_DEBUG */
+
+static unsigned char dht11_decode_byte(char *bits)
+{
+	unsigned char ret = 0;
+	int i;
+
+	for (i = 0; i < 8; ++i) {
+		ret <<= 1;
+		if (bits[i])
+			++ret;
+	}
+
+	return ret;
+}
+
+static int dht11_decode(struct dht11 *dht11, int offset)
+{
+	int i, t;
+	char bits[DHT11_BITS_PER_READ];
+	unsigned char temp_int, temp_dec, hum_int, hum_dec, checksum;
+
+	for (i = 0; i < DHT11_BITS_PER_READ; ++i) {
+		t = dht11->edges[offset + 2 * i + 2].ts -
+			dht11->edges[offset + 2 * i + 1].ts;
+		if (!dht11->edges[offset + 2 * i + 1].value) {
+			dev_dbg(dht11->dev,
+				"lost synchronisation at edge %d\n",
+				offset + 2 * i + 1);
+			return -EIO;
+		}
+		bits[i] = t > DHT11_THRESHOLD;
+	}
+
+	hum_int = dht11_decode_byte(bits);
+	hum_dec = dht11_decode_byte(&bits[8]);
+	temp_int = dht11_decode_byte(&bits[16]);
+	temp_dec = dht11_decode_byte(&bits[24]);
+	checksum = dht11_decode_byte(&bits[32]);
+
+	if (((hum_int + hum_dec + temp_int + temp_dec) & 0xff) != checksum) {
+		dev_dbg(dht11->dev, "invalid checksum\n");
+		return -EIO;
+	}
+
+	dht11->timestamp = ktime_get_boot_ns();
+	if (hum_int < 20) {  /* DHT22 */
+		dht11->temperature = (((temp_int & 0x7f) << 8) + temp_dec) *
+					((temp_int & 0x80) ? -100 : 100);
+		dht11->humidity = ((hum_int << 8) + hum_dec) * 100;
+	} else  {  /* DHT11 */
+		dht11->temperature = temp_int;;
+		dht11->humidity = hum_int;;
+	} 
+
+	return 0;
+}
+
+/*
+ * IRQ handler called on GPIO edges
+ */
+static irqreturn_t dht11_handle_irq(int irq, void *data)
+{
+	struct iio_dev *iio = data;
+	struct dht11 *dht11 = iio_priv(iio);
+
+	/* TODO: Consider making the handler safe for IRQ sharing */
+	if (dht11->num_edges < DHT11_EDGES_PER_READ && dht11->num_edges >= 0) {
+		dht11->edges[dht11->num_edges].ts = ktime_get_boot_ns();
+		dht11->edges[dht11->num_edges++].value =
+						gpio_get_value(dht11->gpio);
+
+		if (dht11->num_edges >= DHT11_EDGES_PER_READ)
+			complete(&dht11->completion);
+	}
+
+	return IRQ_HANDLED;
+}
+
+static int dht11_read_raw(struct iio_dev *iio_dev,
+			  const struct iio_chan_spec *chan,
+			int *val, int *val2, long m)
+{
+	struct dht11 *dht11 = iio_priv(iio_dev);
+	int ret, timeres, offset;
+
+	mutex_lock(&dht11->lock);
+	if (dht11->timestamp + DHT11_DATA_VALID_TIME < ktime_get_boot_ns()) {
+		timeres = ktime_get_resolution_ns();
+		dev_dbg(dht11->dev, "current timeresolution: %dns\n", timeres);
+		if (timeres > DHT11_MIN_TIMERES) {
+			dev_err(dht11->dev, "timeresolution %dns too low\n",
+				timeres);
+			/* In theory a better clock could become available
+			 * at some point ... and there is no error code
+			 * that really fits better.
+			 */
+			ret = -EAGAIN;
+			goto err;
+		}
+		if (timeres > DHT11_AMBIG_LOW && timeres < DHT11_AMBIG_HIGH)
+			dev_warn(dht11->dev,
+				 "timeresolution: %dns - decoding ambiguous\n",
+				 timeres);
+
+		reinit_completion(&dht11->completion);
+
+		dht11->num_edges = 0;
+		ret = gpio_direction_output(dht11->gpio, 0);
+		if (ret)
+			goto err;
+		usleep_range(DHT11_START_TRANSMISSION_MIN,
+			     DHT11_START_TRANSMISSION_MAX);
+		ret = gpio_direction_input(dht11->gpio);
+		if (ret)
+			goto err;
+
+		ret = request_irq(dht11->irq, dht11_handle_irq,
+				  IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
+				  iio_dev->name, iio_dev);
+		if (ret)
+			goto err;
+
+		ret = wait_for_completion_killable_timeout(&dht11->completion,
+							   HZ);
+
+		free_irq(dht11->irq, iio_dev);
+
+#ifdef CONFIG_DYNAMIC_DEBUG
+		dht11_edges_print(dht11);
+#endif
+
+		if (ret == 0 && dht11->num_edges < DHT11_EDGES_PER_READ - 1) {
+			dev_err(dht11->dev, "Only %d signal edges detected\n",
+				dht11->num_edges);
+			ret = -ETIMEDOUT;
+		}
+		if (ret < 0)
+			goto err;
+
+		offset = DHT11_EDGES_PREAMBLE +
+				dht11->num_edges - DHT11_EDGES_PER_READ;
+		for (; offset >= 0; --offset) {
+			ret = dht11_decode(dht11, offset);
+			if (!ret)
+				break;
+		}
+
+		if (ret)
+			goto err;
+	}
+
+	ret = IIO_VAL_INT;
+	if (chan->type == IIO_TEMP)
+		*val = dht11->temperature;
+	else if (chan->type == IIO_HUMIDITYRELATIVE)
+		*val = dht11->humidity;
+	else
+		ret = -EINVAL;
+err:
+	dht11->num_edges = -1;
+	mutex_unlock(&dht11->lock);
+	return ret;
+}
+
+static const struct iio_info dht11_iio_info = {
+	.driver_module		= THIS_MODULE,
+	.read_raw		= dht11_read_raw,
+};
+
+static const struct iio_event_spec dht11_temp_events[] = {
+	{
+		.type = IIO_EV_TYPE_THRESH,
+		.dir = IIO_EV_DIR_RISING,
+		.mask_separate = BIT(IIO_EV_INFO_VALUE),
+	}, {
+		.type = IIO_EV_TYPE_THRESH,
+		.dir = IIO_EV_DIR_FALLING,
+		.mask_separate = BIT(IIO_EV_INFO_VALUE),
+	}, {
+		.type = IIO_EV_TYPE_THRESH,
+		.dir = IIO_EV_DIR_EITHER,
+		.mask_separate = BIT(IIO_EV_INFO_ENABLE),
+	},
+};
+
+static const struct iio_chan_spec dht11_chan_spec[] = {
+	{ .type = IIO_TEMP,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), 
+		.scan_index = 0,
+		.scan_type = {
+			.sign = 's',
+			.realbits = 8,
+			.storagebits = 8,
+		},
+		.event_spec = dht11_temp_events,
+		.num_event_specs = ARRAY_SIZE(dht11_temp_events),
+	},
+	{ .type = IIO_HUMIDITYRELATIVE,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), 
+		.scan_index = 1,
+		.scan_type = {
+			.sign = 's',
+			.realbits = 8,
+			.storagebits = 8,
+		},
+	}
+};
+
+static const struct of_device_id dht11_dt_ids[] = {
+	{ .compatible = "dht11", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, dht11_dt_ids);
+
+static int dht11_buf_preenable(struct iio_dev *indio_dev)
+{
+	return 0;
+}
+
+static int dht11_buf_postenable(struct iio_dev *indio_dev)
+{
+	struct dht11 *dht11 = iio_priv(indio_dev);
+	
+	/* start work */
+	schedule_delayed_work(&dht11->work, 1);
+	
+	return 0;
+}
+
+static int dht11_buf_postdisable(struct iio_dev *indio_dev)
+{
+	struct dht11 *dht11 = iio_priv(indio_dev);
+
+	/* cancel work */
+	cancel_delayed_work_sync(&dht11->work);
+	return 0;
+}
+
+
+static const struct iio_buffer_setup_ops dht11_buf_setup_ops = {
+	.preenable = dht11_buf_preenable,
+	.postenable = dht11_buf_postenable,
+	.postdisable = dht11_buf_postdisable,
+};
+
+
+static irqreturn_t dht11_triggered_buf_handle(int irq, void * p)
+{
+	struct iio_poll_func *pf = p;
+	pf->timestamp = iio_get_time_ns(pf->indio_dev);
+	return IRQ_WAKE_THREAD;
+}
+
+static irqreturn_t dht11_triggered_buf_thread(int irq, void * p)
+{
+	/* read data */
+	struct iio_poll_func *pf = p;
+	struct iio_dev *iio_dev = pf->indio_dev;	
+	struct dht11 *dht11 = iio_priv(iio_dev);
+	
+	int ret, timeres, offset;
+	uint8_t vals[2];
+	
+	/* read dht11 */
+	mutex_lock(&dht11->lock);
+	if (dht11->timestamp + DHT11_DATA_VALID_TIME < ktime_get_boot_ns()) {
+		timeres = ktime_get_resolution_ns();
+		dev_dbg(dht11->dev, "current timeresolution: %dns\n", timeres);
+		if (timeres > DHT11_MIN_TIMERES) {
+			dev_err(dht11->dev, "timeresolution %dns too low\n",
+				timeres);
+			/* In theory a better clock could become available
+			 * at some point ... and there is no error code
+			 * that really fits better.
+			 */
+			ret = -EAGAIN;
+			goto err;
+		}
+		if (timeres > DHT11_AMBIG_LOW && timeres < DHT11_AMBIG_HIGH)
+			dev_warn(dht11->dev,
+				 "timeresolution: %dns - decoding ambiguous\n",
+				 timeres);
+
+		reinit_completion(&dht11->completion);
+
+		dht11->num_edges = 0;
+		ret = gpio_direction_output(dht11->gpio, 0);
+		if (ret)
+			goto err;
+		usleep_range(DHT11_START_TRANSMISSION_MIN,
+				 DHT11_START_TRANSMISSION_MAX);
+		ret = gpio_direction_input(dht11->gpio);
+		if (ret)
+			goto err;
+
+		ret = request_irq(dht11->irq, dht11_handle_irq,
+				  IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
+				  iio_dev->name, iio_dev);
+		if (ret)
+			goto err;
+
+		ret = wait_for_completion_killable_timeout(&dht11->completion,
+							   HZ);
+
+		free_irq(dht11->irq, iio_dev);
+
+#ifdef CONFIG_DYNAMIC_DEBUG
+		dht11_edges_print(dht11);
+#endif
+
+		if (ret == 0 && dht11->num_edges < DHT11_EDGES_PER_READ - 1) {
+			dev_err(dht11->dev, "Only %d signal edges detected\n",
+				dht11->num_edges);
+			ret = -ETIMEDOUT;
+		}
+		if (ret < 0)
+			goto err;
+
+		offset = DHT11_EDGES_PREAMBLE +
+				dht11->num_edges - DHT11_EDGES_PER_READ;
+		for (; offset >= 0; --offset) {
+			ret = dht11_decode(dht11, offset);
+			if (!ret)
+				break;
+		}
+
+		if (ret)
+			goto err;
+	}
+
+	vals[0] = dht11->temperature;
+	vals[1] = dht11->humidity;
+	
+	/* put data into iio_buffer */
+	iio_push_to_buffers(iio_dev, vals);
+
+	if (vals[0] > 30)
+	{
+		iio_push_event(iio_dev,
+				   IIO_UNMOD_EVENT_CODE(IIO_TEMP, 0,
+						IIO_EV_TYPE_THRESH, IIO_EV_DIR_RISING),
+				   iio_get_time_ns(iio_dev));
+	}
+	
+err:
+	dht11->num_edges = -1;
+	mutex_unlock(&dht11->lock);
+
+	iio_trigger_notify_done(iio_dev->trig);
+
+	return IRQ_HANDLED;
+}
+
+
+static irqreturn_t dht11_event_handler(int irq, void *private)
+{
+	struct iio_poll_func *pf = private;
+	struct iio_dev *idev = pf->indio_dev;
+
+	iio_push_event(idev,
+			   IIO_UNMOD_EVENT_CODE(IIO_TEMP, 0,
+					IIO_EV_TYPE_THRESH, IIO_EV_DIR_RISING),
+			   iio_get_time_ns(idev));
+
+	iio_trigger_notify_done(idev->trig);
+
+	return IRQ_HANDLED;
+}
+
+static int dht11_buffer_init(struct iio_dev *indio_dev)
+{
+#if 0	
+	struct iio_buffer *buffer;
+
+	buffer = iio_kfifo_allocate();
+	if (!buffer)
+		return -ENOMEM;
+
+	iio_device_attach_buffer(indio_dev, buffer);
+
+	/* Ring buffer functions - here trigger setup related */
+	indio_dev->setup_ops = &dht11_buf_setup_ops;
+
+	return 0;
+#else
+	//int ret = iio_triggered_event_setup(indio_dev, NULL, dht11_event_handler);
+	//if (ret)
+	//	return ret;
+	
+	return iio_triggered_buffer_setup(indio_dev, dht11_triggered_buf_handle, dht11_triggered_buf_thread, NULL);
+#endif
+}
+
+static void dht11_work(struct work_struct *work)
+{
+	struct dht11 *dht11 = container_of(work, struct dht11, work.work);
+	int ret, timeres, offset;
+	struct iio_dev *iio_dev = dht11->iio;
+	uint8_t vals[2];
+	
+	/* read dht11 */
+	mutex_lock(&dht11->lock);
+	if (dht11->timestamp + DHT11_DATA_VALID_TIME < ktime_get_boot_ns()) {
+		timeres = ktime_get_resolution_ns();
+		dev_dbg(dht11->dev, "current timeresolution: %dns\n", timeres);
+		if (timeres > DHT11_MIN_TIMERES) {
+			dev_err(dht11->dev, "timeresolution %dns too low\n",
+				timeres);
+			/* In theory a better clock could become available
+			 * at some point ... and there is no error code
+			 * that really fits better.
+			 */
+			ret = -EAGAIN;
+			goto err;
+		}
+		if (timeres > DHT11_AMBIG_LOW && timeres < DHT11_AMBIG_HIGH)
+			dev_warn(dht11->dev,
+				 "timeresolution: %dns - decoding ambiguous\n",
+				 timeres);
+
+		reinit_completion(&dht11->completion);
+
+		dht11->num_edges = 0;
+		ret = gpio_direction_output(dht11->gpio, 0);
+		if (ret)
+			goto err;
+		usleep_range(DHT11_START_TRANSMISSION_MIN,
+				 DHT11_START_TRANSMISSION_MAX);
+		ret = gpio_direction_input(dht11->gpio);
+		if (ret)
+			goto err;
+
+		ret = request_irq(dht11->irq, dht11_handle_irq,
+				  IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
+				  iio_dev->name, iio_dev);
+		if (ret)
+			goto err;
+
+		ret = wait_for_completion_killable_timeout(&dht11->completion,
+							   HZ);
+
+		free_irq(dht11->irq, iio_dev);
+
+#ifdef CONFIG_DYNAMIC_DEBUG
+		dht11_edges_print(dht11);
+#endif
+
+		if (ret == 0 && dht11->num_edges < DHT11_EDGES_PER_READ - 1) {
+			dev_err(dht11->dev, "Only %d signal edges detected\n",
+				dht11->num_edges);
+			ret = -ETIMEDOUT;
+		}
+		if (ret < 0)
+			goto err;
+
+		offset = DHT11_EDGES_PREAMBLE +
+				dht11->num_edges - DHT11_EDGES_PER_READ;
+		for (; offset >= 0; --offset) {
+			ret = dht11_decode(dht11, offset);
+			if (!ret)
+				break;
+		}
+
+		if (ret)
+			goto err;
+	}
+
+	vals[0] = dht11->temperature;
+	vals[1] = dht11->humidity;
+	
+	/* put data into iio_buffer */
+	iio_push_to_buffers(iio_dev, vals);
+	
+err:
+	dht11->num_edges = -1;
+	mutex_unlock(&dht11->lock);
+	
+	/* re-start work */
+	if (ret)
+	{
+		/* 有错误 */
+		schedule_delayed_work(&dht11->work, 0);
+	}
+	else
+	{
+		schedule_delayed_work(&dht11->work, HZ);
+	}
+}
+
+static const unsigned long dht11_scan_masks[] = {0x3, 0};
+
+static int dht11_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *node = dev->of_node;
+	struct dht11 *dht11;
+	struct iio_dev *iio;
+	int ret;
+
+	iio = devm_iio_device_alloc(dev, sizeof(*dht11));
+	if (!iio) {
+		dev_err(dev, "Failed to allocate IIO device\n");
+		return -ENOMEM;
+	}
+
+	dht11 = iio_priv(iio);
+	dht11->dev = dev;
+	dht11->iio = iio;
+
+	ret = of_get_gpio(node, 0);
+	if (ret < 0)
+		return ret;
+	dht11->gpio = ret;
+	ret = devm_gpio_request_one(dev, dht11->gpio, GPIOF_IN, pdev->name);
+	if (ret)
+		return ret;
+
+	dht11->irq = gpio_to_irq(dht11->gpio);
+	if (dht11->irq < 0) {
+		dev_err(dev, "GPIO %d has no interrupt\n", dht11->gpio);
+		return -EINVAL;
+	}
+
+	dht11->timestamp = ktime_get_boot_ns() - DHT11_DATA_VALID_TIME - 1;
+	dht11->num_edges = -1;
+
+	platform_set_drvdata(pdev, iio);
+
+	init_completion(&dht11->completion);
+	mutex_init(&dht11->lock);
+	iio->name = pdev->name;
+	iio->dev.parent = &pdev->dev;
+	iio->info = &dht11_iio_info;
+	iio->modes = INDIO_DIRECT_MODE | INDIO_BUFFER_SOFTWARE;
+	iio->channels = dht11_chan_spec;
+	iio->num_channels = ARRAY_SIZE(dht11_chan_spec);
+	iio->available_scan_masks = dht11_scan_masks;
+
+	dht11_buffer_init(iio);
+
+	/* init work */
+	INIT_DELAYED_WORK(&dht11->work, dht11_work);
+
+	return devm_iio_device_register(dev, iio);
+}
+
+static struct platform_driver dht11_driver = {
+	.driver = {
+		.name	= DRIVER_NAME,
+		.of_match_table = dht11_dt_ids,
+	},
+	.probe  = dht11_probe,
+};
+
+module_platform_driver(dht11_driver);
+
+MODULE_AUTHOR("Harald Geyer <harald@ccbib.org>");
+MODULE_DESCRIPTION("DHT11 humidity/temperature sensor driver");
+MODULE_LICENSE("GPL v2");

IMX6ULL/source/14_iio/05_dht11_iio_event/dht11.dts

@@ -0,0 +1,4 @@
+humidity_sensor {
+	compatible = "dht11";
+    gpios = <&gpio4 19 GPIO_ACTIVE_HIGH>;
+};

IMX6ULL/source/14_iio/05_dht11_iio_event/dht11_test.c

@@ -0,0 +1,50 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <string.h>
+
+#include <sys/ioctl.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include <linux/types.h>
+#include <linux/iio/events.h>
+
+int main(int argc, char **argv)
+{
+	int fd;
+	int ret;
+	int event_fd;
+	struct iio_event_data event;
+	
+	if (argc != 2)
+	{
+		printf("Usage: %s /dev/iio\\:deviceX\n", argv[0]);
+		return 0;
+	}
+
+	fd = open(argv[1], O_RDWR);  // /dev/iio:device2
+	if (fd < 0) {
+		printf("can not open %s\n", argv[1]);
+		return -1;
+	}
+
+	ret = ioctl(fd, IIO_GET_EVENT_FD_IOCTL, &event_fd);
+	if (ret < 0) {
+		printf("can not get event fd\n");
+		return -1;
+	}
+
+	while (1)
+	{
+		ret = read(event_fd, &event, sizeof(event));
+		if (ret == sizeof(event))
+		{
+			printf("Get event: 0x%lx\n", event.id);
+		}
+	}
+
+	return 0;
+}
+

IMX6ULL/source/14_iio/06_dht11_iio_event_课堂现场编写/dht11.c

@@ -0,0 +1,751 @@
+/*
+ * DHT11/DHT22 bit banging GPIO driver
+ *
+ * Copyright (c) Harald Geyer <harald@ccbib.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/err.h>
+#include <linux/interrupt.h>
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/printk.h>
+#include <linux/slab.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/sysfs.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/wait.h>
+#include <linux/bitops.h>
+#include <linux/completion.h>
+#include <linux/mutex.h>
+#include <linux/delay.h>
+#include <linux/gpio.h>
+#include <linux/of_gpio.h>
+#include <linux/timekeeping.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/kfifo_buf.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/iio/triggered_buffer.h>
+#include <linux/iio/triggered_event.h>
+#include <linux/iio/events.h>
+
+#define DRIVER_NAME	"dht11"
+
+#define DHT11_DATA_VALID_TIME	2000000000  /* 2s in ns */
+
+#define DHT11_EDGES_PREAMBLE 2
+#define DHT11_BITS_PER_READ 40
+/*
+ * Note that when reading the sensor actually 84 edges are detected, but
+ * since the last edge is not significant, we only store 83:
+ */
+#define DHT11_EDGES_PER_READ (2 * DHT11_BITS_PER_READ + \
+			      DHT11_EDGES_PREAMBLE + 1)
+
+/*
+ * Data transmission timing:
+ * Data bits are encoded as pulse length (high time) on the data line.
+ * 0-bit: 22-30uS -- typically 26uS (AM2302)
+ * 1-bit: 68-75uS -- typically 70uS (AM2302)
+ * The acutal timings also depend on the properties of the cable, with
+ * longer cables typically making pulses shorter.
+ *
+ * Our decoding depends on the time resolution of the system:
+ * timeres > 34uS ... don't know what a 1-tick pulse is
+ * 34uS > timeres > 30uS ... no problem (30kHz and 32kHz clocks)
+ * 30uS > timeres > 23uS ... don't know what a 2-tick pulse is
+ * timeres < 23uS ... no problem
+ *
+ * Luckily clocks in the 33-44kHz range are quite uncommon, so we can
+ * support most systems if the threshold for decoding a pulse as 1-bit
+ * is chosen carefully. If somebody really wants to support clocks around
+ * 40kHz, where this driver is most unreliable, there are two options.
+ * a) select an implementation using busy loop polling on those systems
+ * b) use the checksum to do some probabilistic decoding
+ */
+#define DHT11_START_TRANSMISSION_MIN	18000  /* us */
+#define DHT11_START_TRANSMISSION_MAX	20000  /* us */
+#define DHT11_MIN_TIMERES	34000  /* ns */
+#define DHT11_THRESHOLD		49000  /* ns */
+#define DHT11_AMBIG_LOW		23000  /* ns */
+#define DHT11_AMBIG_HIGH	30000  /* ns */
+
+struct dht11 {
+	struct device			*dev;
+
+	int				gpio;
+	int				irq;
+
+	struct completion		completion;
+	/* The iio sysfs interface doesn't prevent concurrent reads: */
+	struct mutex			lock;
+
+	s64				timestamp;
+	int				temperature;
+	int				humidity;
+
+	/* num_edges: -1 means "no transmission in progress" */
+	int				num_edges;
+	struct {s64 ts; int value; }	edges[DHT11_EDGES_PER_READ];
+	struct delayed_work		work;
+	struct iio_dev *iio;
+	int temp_ev_enable;
+	int temp_thres_up;
+	int temp_thres_down;
+};
+
+#ifdef CONFIG_DYNAMIC_DEBUG
+/*
+ * dht11_edges_print: show the data as actually received by the
+ *                    driver.
+ */
+static void dht11_edges_print(struct dht11 *dht11)
+{
+	int i;
+
+	dev_dbg(dht11->dev, "%d edges detected:\n", dht11->num_edges);
+	for (i = 1; i < dht11->num_edges; ++i) {
+		dev_dbg(dht11->dev, "%d: %lld ns %s\n", i,
+			dht11->edges[i].ts - dht11->edges[i - 1].ts,
+			dht11->edges[i - 1].value ? "high" : "low");
+	}
+}
+#endif /* CONFIG_DYNAMIC_DEBUG */
+
+static unsigned char dht11_decode_byte(char *bits)
+{
+	unsigned char ret = 0;
+	int i;
+
+	for (i = 0; i < 8; ++i) {
+		ret <<= 1;
+		if (bits[i])
+			++ret;
+	}
+
+	return ret;
+}
+
+static int dht11_decode(struct dht11 *dht11, int offset)
+{
+	int i, t;
+	char bits[DHT11_BITS_PER_READ];
+	unsigned char temp_int, temp_dec, hum_int, hum_dec, checksum;
+
+	for (i = 0; i < DHT11_BITS_PER_READ; ++i) {
+		t = dht11->edges[offset + 2 * i + 2].ts -
+			dht11->edges[offset + 2 * i + 1].ts;
+		if (!dht11->edges[offset + 2 * i + 1].value) {
+			dev_dbg(dht11->dev,
+				"lost synchronisation at edge %d\n",
+				offset + 2 * i + 1);
+			return -EIO;
+		}
+		bits[i] = t > DHT11_THRESHOLD;
+	}
+
+	hum_int = dht11_decode_byte(bits);
+	hum_dec = dht11_decode_byte(&bits[8]);
+	temp_int = dht11_decode_byte(&bits[16]);
+	temp_dec = dht11_decode_byte(&bits[24]);
+	checksum = dht11_decode_byte(&bits[32]);
+
+	if (((hum_int + hum_dec + temp_int + temp_dec) & 0xff) != checksum) {
+		dev_dbg(dht11->dev, "invalid checksum\n");
+		return -EIO;
+	}
+
+	dht11->timestamp = ktime_get_boot_ns();
+	if (hum_int < 20) {  /* DHT22 */
+		dht11->temperature = (((temp_int & 0x7f) << 8) + temp_dec) *
+					((temp_int & 0x80) ? -100 : 100);
+		dht11->humidity = ((hum_int << 8) + hum_dec) * 100;
+	} else  {  /* DHT11 */
+		dht11->temperature = temp_int;;
+		dht11->humidity = hum_int;;
+	} 
+
+	return 0;
+}
+
+/*
+ * IRQ handler called on GPIO edges
+ */
+static irqreturn_t dht11_handle_irq(int irq, void *data)
+{
+	struct iio_dev *iio = data;
+	struct dht11 *dht11 = iio_priv(iio);
+
+	/* TODO: Consider making the handler safe for IRQ sharing */
+	if (dht11->num_edges < DHT11_EDGES_PER_READ && dht11->num_edges >= 0) {
+		dht11->edges[dht11->num_edges].ts = ktime_get_boot_ns();
+		dht11->edges[dht11->num_edges++].value =
+						gpio_get_value(dht11->gpio);
+
+		if (dht11->num_edges >= DHT11_EDGES_PER_READ)
+			complete(&dht11->completion);
+	}
+
+	return IRQ_HANDLED;
+}
+
+static int dht11_read_raw(struct iio_dev *iio_dev,
+			  const struct iio_chan_spec *chan,
+			int *val, int *val2, long m)
+{
+	struct dht11 *dht11 = iio_priv(iio_dev);
+	int ret, timeres, offset;
+
+	mutex_lock(&dht11->lock);
+	if (dht11->timestamp + DHT11_DATA_VALID_TIME < ktime_get_boot_ns()) {
+		timeres = ktime_get_resolution_ns();
+		dev_dbg(dht11->dev, "current timeresolution: %dns\n", timeres);
+		if (timeres > DHT11_MIN_TIMERES) {
+			dev_err(dht11->dev, "timeresolution %dns too low\n",
+				timeres);
+			/* In theory a better clock could become available
+			 * at some point ... and there is no error code
+			 * that really fits better.
+			 */
+			ret = -EAGAIN;
+			goto err;
+		}
+		if (timeres > DHT11_AMBIG_LOW && timeres < DHT11_AMBIG_HIGH)
+			dev_warn(dht11->dev,
+				 "timeresolution: %dns - decoding ambiguous\n",
+				 timeres);
+
+		reinit_completion(&dht11->completion);
+
+		dht11->num_edges = 0;
+		ret = gpio_direction_output(dht11->gpio, 0);
+		if (ret)
+			goto err;
+		usleep_range(DHT11_START_TRANSMISSION_MIN,
+			     DHT11_START_TRANSMISSION_MAX);
+		ret = gpio_direction_input(dht11->gpio);
+		if (ret)
+			goto err;
+
+		ret = request_irq(dht11->irq, dht11_handle_irq,
+				  IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
+				  iio_dev->name, iio_dev);
+		if (ret)
+			goto err;
+
+		ret = wait_for_completion_killable_timeout(&dht11->completion,
+							   HZ);
+
+		free_irq(dht11->irq, iio_dev);
+
+#ifdef CONFIG_DYNAMIC_DEBUG
+		dht11_edges_print(dht11);
+#endif
+
+		if (ret == 0 && dht11->num_edges < DHT11_EDGES_PER_READ - 1) {
+			dev_err(dht11->dev, "Only %d signal edges detected\n",
+				dht11->num_edges);
+			ret = -ETIMEDOUT;
+		}
+		if (ret < 0)
+			goto err;
+
+		offset = DHT11_EDGES_PREAMBLE +
+				dht11->num_edges - DHT11_EDGES_PER_READ;
+		for (; offset >= 0; --offset) {
+			ret = dht11_decode(dht11, offset);
+			if (!ret)
+				break;
+		}
+
+		if (ret)
+			goto err;
+	}
+
+	ret = IIO_VAL_INT;
+	if (chan->type == IIO_TEMP)
+		*val = dht11->temperature;
+	else if (chan->type == IIO_HUMIDITYRELATIVE)
+		*val = dht11->humidity;
+	else
+		ret = -EINVAL;
+err:
+	dht11->num_edges = -1;
+	mutex_unlock(&dht11->lock);
+	return ret;
+}
+
+static int dht11_read_event_config(struct iio_dev *idev,
+					const struct iio_chan_spec *chan,
+					enum iio_event_type type,
+					enum iio_event_direction dir)
+{
+	struct dht11 *dht11 = iio_priv(idev);
+
+	return !!dht11->temp_ev_enable;
+}
+
+static int dht11_write_event_config(struct iio_dev *idev,
+					 const struct iio_chan_spec *chan,
+					 enum iio_event_type type,
+					 enum iio_event_direction dir, int state)
+{
+	struct dht11 *dht11 = iio_priv(idev);
+
+	dht11->temp_ev_enable = state;
+
+	return 0;
+}
+
+static int dht11_read_event_value(struct iio_dev *idev,
+				   const struct iio_chan_spec *chan,
+				   enum iio_event_type type,
+				   enum iio_event_direction dir,
+				   enum iio_event_info info,
+				   int *val, int *val2)
+{
+	struct dht11 *dht11 = iio_priv(idev);
+
+	if (chan->type == IIO_TEMP)
+	{
+		if (dir == IIO_EV_DIR_FALLING) {
+			*val = dht11->temp_thres_down;
+		} else {
+			*val = dht11->temp_thres_up;
+		}
+	}
+
+	return IIO_VAL_INT;
+}
+
+static int dht11_write_event_value(struct iio_dev *idev,
+					const struct iio_chan_spec *chan,
+					enum iio_event_type type,
+					enum iio_event_direction dir,
+					enum iio_event_info info,
+					int val, int val2)
+{
+	struct dht11 *dht11 = iio_priv(idev);
+
+	if (chan->type == IIO_TEMP)
+	{
+		if (dir == IIO_EV_DIR_FALLING) {
+			dht11->temp_thres_down = val;
+		} else {
+			dht11->temp_thres_up = val;
+		}
+	}
+
+	return IIO_VAL_INT;
+}
+
+static const struct iio_info dht11_iio_info = {
+	.driver_module		= THIS_MODULE,
+	.read_raw		= dht11_read_raw,
+	.write_event_value = dht11_write_event_value,
+	.read_event_value  = dht11_read_event_value,
+	.read_event_config = dht11_read_event_config,
+	.write_event_config = dht11_write_event_config,	
+};
+
+static const struct iio_event_spec dht11_temp_events[] = {
+	{
+		.type = IIO_EV_TYPE_THRESH,
+		.dir = IIO_EV_DIR_RISING,
+		.mask_separate = BIT(IIO_EV_INFO_VALUE),
+	}, {
+		.type = IIO_EV_TYPE_THRESH,
+		.dir = IIO_EV_DIR_FALLING,
+		.mask_separate = BIT(IIO_EV_INFO_VALUE),
+	}, {
+		.type = IIO_EV_TYPE_THRESH,
+		.dir = IIO_EV_DIR_EITHER,
+		.mask_separate = BIT(IIO_EV_INFO_ENABLE),
+	},
+};
+
+
+static const struct iio_chan_spec dht11_chan_spec[] = {
+	{ .type = IIO_TEMP,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), 
+		.scan_index = 0,
+		.scan_type = {
+			.sign = 's',
+			.realbits = 8,
+			.storagebits = 8,
+		},
+
+		.event_spec = dht11_temp_events,
+		.num_event_specs = ARRAY_SIZE(dht11_temp_events),
+
+	},
+	{ .type = IIO_HUMIDITYRELATIVE,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), 
+		.scan_index = 1,
+		.scan_type = {
+			.sign = 's',
+			.realbits = 8,
+			.storagebits = 8,
+		},
+	}
+};
+
+static const struct of_device_id dht11_dt_ids[] = {
+	{ .compatible = "dht11", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, dht11_dt_ids);
+
+static int dht11_buf_preenable(struct iio_dev *indio_dev)
+{
+	return 0;
+}
+
+static int dht11_buf_postenable(struct iio_dev *indio_dev)
+{
+	struct dht11 *dht11 = iio_priv(indio_dev);
+	
+	/* start work */
+	schedule_delayed_work(&dht11->work, 1);
+	
+	return 0;
+}
+
+static int dht11_buf_postdisable(struct iio_dev *indio_dev)
+{
+	struct dht11 *dht11 = iio_priv(indio_dev);
+
+	/* cancel work */
+	cancel_delayed_work_sync(&dht11->work);
+	return 0;
+}
+
+
+static const struct iio_buffer_setup_ops dht11_buf_setup_ops = {
+	.preenable = dht11_buf_preenable,
+	.postenable = dht11_buf_postenable,
+	.postdisable = dht11_buf_postdisable,
+};
+
+
+static irqreturn_t dht11_triggered_buf_handle(int irq, void * p)
+{
+	struct iio_poll_func *pf = p;
+	pf->timestamp = iio_get_time_ns(pf->indio_dev);
+	return IRQ_WAKE_THREAD;
+}
+
+static irqreturn_t dht11_triggered_buf_thread(int irq, void * p)
+{
+	/* read data */
+	struct iio_poll_func *pf = p;
+	struct iio_dev *iio_dev = pf->indio_dev;	
+	struct dht11 *dht11 = iio_priv(iio_dev);
+	
+	int ret, timeres, offset;
+	uint8_t vals[2];
+	
+	/* read dht11 */
+	mutex_lock(&dht11->lock);
+	if (dht11->timestamp + DHT11_DATA_VALID_TIME < ktime_get_boot_ns()) {
+		timeres = ktime_get_resolution_ns();
+		dev_dbg(dht11->dev, "current timeresolution: %dns\n", timeres);
+		if (timeres > DHT11_MIN_TIMERES) {
+			dev_err(dht11->dev, "timeresolution %dns too low\n",
+				timeres);
+			/* In theory a better clock could become available
+			 * at some point ... and there is no error code
+			 * that really fits better.
+			 */
+			ret = -EAGAIN;
+			goto err;
+		}
+		if (timeres > DHT11_AMBIG_LOW && timeres < DHT11_AMBIG_HIGH)
+			dev_warn(dht11->dev,
+				 "timeresolution: %dns - decoding ambiguous\n",
+				 timeres);
+
+		reinit_completion(&dht11->completion);
+
+		dht11->num_edges = 0;
+		ret = gpio_direction_output(dht11->gpio, 0);
+		if (ret)
+			goto err;
+		usleep_range(DHT11_START_TRANSMISSION_MIN,
+				 DHT11_START_TRANSMISSION_MAX);
+		ret = gpio_direction_input(dht11->gpio);
+		if (ret)
+			goto err;
+
+		ret = request_irq(dht11->irq, dht11_handle_irq,
+				  IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
+				  iio_dev->name, iio_dev);
+		if (ret)
+			goto err;
+
+		ret = wait_for_completion_killable_timeout(&dht11->completion,
+							   HZ);
+
+		free_irq(dht11->irq, iio_dev);
+
+#ifdef CONFIG_DYNAMIC_DEBUG
+		dht11_edges_print(dht11);
+#endif
+
+		if (ret == 0 && dht11->num_edges < DHT11_EDGES_PER_READ - 1) {
+			dev_err(dht11->dev, "Only %d signal edges detected\n",
+				dht11->num_edges);
+			ret = -ETIMEDOUT;
+		}
+		if (ret < 0)
+			goto err;
+
+		offset = DHT11_EDGES_PREAMBLE +
+				dht11->num_edges - DHT11_EDGES_PER_READ;
+		for (; offset >= 0; --offset) {
+			ret = dht11_decode(dht11, offset);
+			if (!ret)
+				break;
+		}
+
+		if (ret)
+			goto err;
+	}
+
+	vals[0] = dht11->temperature;
+	vals[1] = dht11->humidity;
+	
+	/* put data into iio_buffer */
+	iio_push_to_buffers(iio_dev, vals);
+
+	if (dht11->temp_ev_enable)
+	{
+		if (vals[0] > dht11->temp_thres_up)
+		{
+			iio_push_event(iio_dev,
+					   IIO_UNMOD_EVENT_CODE(IIO_TEMP, 0,
+							IIO_EV_TYPE_THRESH, IIO_EV_DIR_RISING),
+					   iio_get_time_ns(iio_dev));
+		}
+
+		if (vals[0] < dht11->temp_thres_down)
+		{
+			iio_push_event(iio_dev,
+					   IIO_UNMOD_EVENT_CODE(IIO_TEMP, 0,
+							IIO_EV_TYPE_THRESH, IIO_EV_DIR_FALLING),
+					   iio_get_time_ns(iio_dev));
+		}
+
+	}
+	
+err:
+	dht11->num_edges = -1;
+	mutex_unlock(&dht11->lock);
+
+	iio_trigger_notify_done(iio_dev->trig);
+
+	return IRQ_HANDLED;
+}
+
+
+
+static int dht11_buffer_init(struct iio_dev *indio_dev)
+{
+#if 0	
+	struct iio_buffer *buffer;
+
+	buffer = iio_kfifo_allocate();
+	if (!buffer)
+		return -ENOMEM;
+
+	iio_device_attach_buffer(indio_dev, buffer);
+
+	/* Ring buffer functions - here trigger setup related */
+	indio_dev->setup_ops = &dht11_buf_setup_ops;
+
+	return 0;
+#else
+	return iio_triggered_buffer_setup(indio_dev, dht11_triggered_buf_handle, dht11_triggered_buf_thread, NULL);
+#endif
+}
+
+static void dht11_work(struct work_struct *work)
+{
+	struct dht11 *dht11 = container_of(work, struct dht11, work.work);
+	int ret, timeres, offset;
+	struct iio_dev *iio_dev = dht11->iio;
+	uint8_t vals[2];
+	
+	/* read dht11 */
+	mutex_lock(&dht11->lock);
+	if (dht11->timestamp + DHT11_DATA_VALID_TIME < ktime_get_boot_ns()) {
+		timeres = ktime_get_resolution_ns();
+		dev_dbg(dht11->dev, "current timeresolution: %dns\n", timeres);
+		if (timeres > DHT11_MIN_TIMERES) {
+			dev_err(dht11->dev, "timeresolution %dns too low\n",
+				timeres);
+			/* In theory a better clock could become available
+			 * at some point ... and there is no error code
+			 * that really fits better.
+			 */
+			ret = -EAGAIN;
+			goto err;
+		}
+		if (timeres > DHT11_AMBIG_LOW && timeres < DHT11_AMBIG_HIGH)
+			dev_warn(dht11->dev,
+				 "timeresolution: %dns - decoding ambiguous\n",
+				 timeres);
+
+		reinit_completion(&dht11->completion);
+
+		dht11->num_edges = 0;
+		ret = gpio_direction_output(dht11->gpio, 0);
+		if (ret)
+			goto err;
+		usleep_range(DHT11_START_TRANSMISSION_MIN,
+				 DHT11_START_TRANSMISSION_MAX);
+		ret = gpio_direction_input(dht11->gpio);
+		if (ret)
+			goto err;
+
+		ret = request_irq(dht11->irq, dht11_handle_irq,
+				  IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
+				  iio_dev->name, iio_dev);
+		if (ret)
+			goto err;
+
+		ret = wait_for_completion_killable_timeout(&dht11->completion,
+							   HZ);
+
+		free_irq(dht11->irq, iio_dev);
+
+#ifdef CONFIG_DYNAMIC_DEBUG
+		dht11_edges_print(dht11);
+#endif
+
+		if (ret == 0 && dht11->num_edges < DHT11_EDGES_PER_READ - 1) {
+			dev_err(dht11->dev, "Only %d signal edges detected\n",
+				dht11->num_edges);
+			ret = -ETIMEDOUT;
+		}
+		if (ret < 0)
+			goto err;
+
+		offset = DHT11_EDGES_PREAMBLE +
+				dht11->num_edges - DHT11_EDGES_PER_READ;
+		for (; offset >= 0; --offset) {
+			ret = dht11_decode(dht11, offset);
+			if (!ret)
+				break;
+		}
+
+		if (ret)
+			goto err;
+	}
+
+	vals[0] = dht11->temperature;
+	vals[1] = dht11->humidity;
+	
+	/* put data into iio_buffer */
+	iio_push_to_buffers(iio_dev, vals);
+	
+err:
+	dht11->num_edges = -1;
+	mutex_unlock(&dht11->lock);
+	
+	/* re-start work */
+	if (ret)
+	{
+		/* 有错误 */
+		schedule_delayed_work(&dht11->work, 0);
+	}
+	else
+	{
+		schedule_delayed_work(&dht11->work, HZ);
+	}
+}
+
+static const unsigned long dht11_scan_masks[] = {0x3, 0};
+
+static int dht11_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *node = dev->of_node;
+	struct dht11 *dht11;
+	struct iio_dev *iio;
+	int ret;
+
+	iio = devm_iio_device_alloc(dev, sizeof(*dht11));
+	if (!iio) {
+		dev_err(dev, "Failed to allocate IIO device\n");
+		return -ENOMEM;
+	}
+
+	dht11 = iio_priv(iio);
+	dht11->dev = dev;
+	dht11->iio = iio;
+
+	ret = of_get_gpio(node, 0);
+	if (ret < 0)
+		return ret;
+	dht11->gpio = ret;
+	ret = devm_gpio_request_one(dev, dht11->gpio, GPIOF_IN, pdev->name);
+	if (ret)
+		return ret;
+
+	dht11->irq = gpio_to_irq(dht11->gpio);
+	if (dht11->irq < 0) {
+		dev_err(dev, "GPIO %d has no interrupt\n", dht11->gpio);
+		return -EINVAL;
+	}
+
+	dht11->timestamp = ktime_get_boot_ns() - DHT11_DATA_VALID_TIME - 1;
+	dht11->num_edges = -1;
+
+	platform_set_drvdata(pdev, iio);
+
+	init_completion(&dht11->completion);
+	mutex_init(&dht11->lock);
+	iio->name = pdev->name;
+	iio->dev.parent = &pdev->dev;
+	iio->info = &dht11_iio_info;
+	iio->modes = INDIO_DIRECT_MODE | INDIO_BUFFER_SOFTWARE;
+	iio->channels = dht11_chan_spec;
+	iio->num_channels = ARRAY_SIZE(dht11_chan_spec);
+	iio->available_scan_masks = dht11_scan_masks;
+
+	dht11_buffer_init(iio);
+
+	/* init work */
+	INIT_DELAYED_WORK(&dht11->work, dht11_work);
+
+	return devm_iio_device_register(dev, iio);
+}
+
+static struct platform_driver dht11_driver = {
+	.driver = {
+		.name	= DRIVER_NAME,
+		.of_match_table = dht11_dt_ids,
+	},
+	.probe  = dht11_probe,
+};
+
+module_platform_driver(dht11_driver);
+
+MODULE_AUTHOR("Harald Geyer <harald@ccbib.org>");
+MODULE_DESCRIPTION("DHT11 humidity/temperature sensor driver");
+MODULE_LICENSE("GPL v2");

IMX6ULL/source/14_iio/06_dht11_iio_event_课堂现场编写/dht11.dts

@@ -0,0 +1,4 @@
+humidity_sensor {
+	compatible = "dht11";
+    gpios = <&gpio4 19 GPIO_ACTIVE_HIGH>;
+};

IMX6ULL/source/14_iio/06_dht11_iio_event_课堂现场编写/dht11_test.c

@@ -0,0 +1,50 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <string.h>
+
+#include <sys/ioctl.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include <linux/types.h>
+#include <linux/iio/events.h>
+
+int main(int argc, char **argv)
+{
+	int fd;
+	int ret;
+	int event_fd;
+	struct iio_event_data event;
+	
+	if (argc != 2)
+	{
+		printf("Usage: %s /dev/iio\\:deviceX\n", argv[0]);
+		return 0;
+	}
+
+	fd = open(argv[1], O_RDWR);  // /dev/iio:device2
+	if (fd < 0) {
+		printf("can not open %s\n", argv[1]);
+		return -1;
+	}
+
+	ret = ioctl(fd, IIO_GET_EVENT_FD_IOCTL, &event_fd);
+	if (ret < 0) {
+		printf("can not get event fd\n");
+		return -1;
+	}
+
+	while (1)
+	{
+		ret = read(event_fd, &event, sizeof(event));
+		if (ret == sizeof(event))
+		{
+			printf("Get event: 0x%lx\n", event.id);
+		}
+	}
+
+	return 0;
+}
+

README.md

@@ -880,41 +880,41 @@ git clone https://e.coding.net/weidongshan/linux/doc_and_source_for_drivers.git
   [05-4-5]_使用media子系统和subdev的APP
   ```
 
-* 2024.10.25 发布IIO"子系统"
+* 2024.10.25 发布"IIO子系统"
 
   ```shell
   01.1_IIO子系统简化框架
   01.2_DHT11操作原理与编程思路
   ```
 
-* 2024.10.31 发布IIO"子系统"
+* 2024.10.31 发布"IIO子系统"
 
   ```shell
   01.3_DHT11驱动程序体验_IMX6ULL
   01.3_DHT11驱动程序体验_STM32MP157
   ```
 
-* 2024.11.05 发布IIO"子系统"
+* 2024.11.05 发布"IIO子系统"
 
   ```shell
   01.4_DHT11驱动程序分析
   01.5_通道的sysfs信息修改与体验
   ```
 
-* 2024.11.07 发布IIO"子系统"
+* 2024.11.07 发布"IIO子系统"
 
   ```shell
   02.1_iio_buffer的核心要素与体验
   ```
 
-* 2024.11.08 发布IIO"子系统"
+* 2024.11.08 发布"IIO子系统"
 
   ```shell
   02.2_增加iio_buffer并体验sysfs
   02.3_实现iio_buffer的写入
   ```
 
-* 2024.11.25  发布IIO"子系统"
+* 2024.11.25  发布"IIO子系统"
 
   ```shell
   03.1_iio_trigger的引入与体验
@@ -923,6 +923,18 @@ git clone https://e.coding.net/weidongshan/linux/doc_and_source_for_drivers.git
   03.4_修改DHT11驱动使用iio_trigger
   ```
 
+* 2024.11.28 完结"IIO子系统"
+
+  ```shell
+  04.1_iio_event的引入与体验
+  04.2_修改DHT11驱动使用iio_event_编程
+  04.3_修改DHT11驱动使用iio_event_上机测试
+  04.4_使用trigger写iio_event(不实用)
+  05.1_驱动示例_IMX6ULL的ADC驱动
+  05.2_驱动示例_STM32MP157的ADC驱动
+  05.3_STM32MP157的ADC驱动分析
+  ```
+
   
 
 ## 6. 联系方式

STM32MP157/doc_pic/14_IIO/04_iio_event的使用.md

@@ -0,0 +1,363 @@
+# iio_event的使用
+
+IIO(Industrial I/O)参考资料：
+
+* 系列文章：https://blog.csdn.net/lickylin/article/details/108177756
+* https://www.cnblogs.com/yongleili717/p/10758691.html
+* 内核文档：https://www.kernel.org/doc/html/v5.3/driver-api/iio
+* 参考内核源码
+  * `drivers\staging\iio\impedance-analyzer\ad5933.c`
+  * `drivers\iio\adc\hi8435.c`
+
+
+
+## 1. iio_event的引入与体验
+
+### 1.1 问题引入与解决方法
+
+以温湿度传感器为例，它的温度值超过极限了，APP如何检测到这个事件？
+
+* APP读取某个设备文件
+* 传感器驱动提供数据：
+  * 比如硬件监测到温度超标时，触发硬件中断，在中断里使用iio_push_event把"事件"写入kfifo
+  * APP读取kfifo得到"事件"
+* iio_trigger提供数据：
+  * 有些硬件没有中断引脚，那么可以使用iio_trigger
+  * iio_trigger直接调用驱动程序提供的的另一个"虚拟中断处理函数"(跟iio_buffer不一样的中断处理函数)
+  * 这个中断处理函数读取硬件数据，使用iio_push_event把"事件"写入kfifo
+
+![image-20241125161222685](pic/image-20241125161222685.png)
+
+### 1.2 怎么表示事件
+
+使用结构体"iio_event_data"表示事件：
+
+![image-20241125163136804](pic/image-20241125163136804.png)
+
+
+
+所谓事件就是一个64位的ID，里面不含有具体的数值：比如它表示温度超高了，但是没有表示温度值是多少。
+
+这个ID如何表示不同的事件呢？如下：
+
+![image-20241125163406036](pic/image-20241125163406036.png)
+
+
+
+示例：
+
+![image-20241125164423639](pic/image-20241125164423639.png)
+
+
+
+### 1.3 上机体验
+
+IMX6ULL的源码：
+
+![image-20241126094637080](pic/image-20241126094637080.png)
+
+STM32MP157的源码：
+
+![image-20241126094715687](pic/image-20241126094715687.png)
+
+#### 1.3.1 IMX6ULL
+
+```shell
+insmod /root/iio-trig-hrtimer.ko
+mkdir  /sys/kernel/config/iio/triggers/hrtimer/timer_abc  # 创建trigger
+cat /sys/bus/iio/devices/trigger1/name             # 可以看到这个trigger
+
+insmod /root/dht11.ko
+cd /sys/bus/iio/devices/iio\:device2/
+echo timer_abc > trigger/current_trigger               # 在设备上使用trigger
+
+echo 1 > scan_elements/in_humidityrelative_en
+echo 1 > scan_elements/in_temp_en
+echo 1 > buffer/enable
+
+# hexdump /dev/iio\:device2
+/root/dht11_test /dev/iio\:device2  # 读取事件
+```
+
+
+
+#### 1.3.2 STM32MP157
+
+```SHELL
+# insmod /root/iio-trig-hrtimer.ko # 157上已经有了这个驱动
+mkdir  /sys/kernel/config/iio/triggers/hrtimer/timer_abc  # 创建trigger
+cat /sys/bus/iio/devices/trigger1/name             # 可以看到这个trigger
+
+insmod /root/dht11.ko
+cd /sys/bus/iio/devices/iio\:device1/
+echo timer_abc > trigger/current_trigger               # 在设备上使用trigger
+
+echo 1 > scan_elements/in_humidityrelative_en
+echo 1 > scan_elements/in_temp_en
+echo 1 > buffer/enable
+
+# hexdump /dev/iio\:device1
+/root/dht11_test /dev/iio\:device1  # 读取事件
+```
+
+
+
+
+
+## 2. iio_event数据流程
+
+### 2.1 驱动程序创建KFIFO
+
+![image-20241125175311198](pic/image-20241125175311198.png)
+
+
+
+### 2.2 驱动程序写KFIFO
+
+![image-20241125175658789](pic/image-20241125175658789.png)
+
+
+
+### 2.3 APP读取KFIFO
+
+示例源码如下：
+
+```c
+int event_fd;
+struct iio_event_data event;
+
+int fd = open("/dev/iio:device2", O_RDWR);
+
+ioctl(fd, IIO_GET_EVENT_FD_IOCTL, &event_fd);
+read(event_fd, &event, sizeof(event));
+```
+
+
+
+## 3. 修改DHT11驱动使用iio_event
+
+IMX6ULL的源码：
+
+![image-20241127102844284](pic/image-20241127102844284.png)
+
+STM32MP157的源码：
+
+![image-20241127102920957](pic/image-20241127102920957.png)
+
+### 3.1 设备表明自己有event能力
+
+在注册iio设备时，会进行如下判断：
+
+![image-20241125193456857](pic/image-20241125193456857.png)
+
+只有设置了indio_dev->info->event_attrs或某个通道的num_event_specs不为0，才会创建KFIFO。
+
+
+
+示例代码如下：
+
+![image-20241125170901645](pic/image-20241125170901645.png)
+
+
+
+这会生成如下sysfs文件：
+
+![image-20241125170929132](pic/image-20241125170929132.png)
+
+
+
+生成sysfs文件的流程为：
+
+```c
+iio_device_register
+	iio_device_register_eventset
+    	__iio_add_event_config_attrs
+            for (j = 0; j < indio_dev->num_channels; j++) {
+                ret = iio_device_add_event_sysfs(indio_dev,
+                                 &indio_dev->channels[j]);
+							iio_device_add_event                                	
+```
+
+
+
+这些sysfs对应的读写函数如下：
+
+![image-20241125171144376](pic/image-20241125171144376.png)
+
+
+
+### 3.2 设备驱动提供sysfs接口函数
+
+比如我们想指定温度的报警值，那么就需要实现这些sysfs的接口函数：
+
+![image-20241125193714139](pic/image-20241125193714139.png)
+
+
+
+### 3.3 上机实验
+
+#### 1.3.1 IMX6ULL
+
+```shell
+insmod /root/iio-trig-hrtimer.ko
+mkdir  /sys/kernel/config/iio/triggers/hrtimer/timer_abc  # 创建trigger
+cat /sys/bus/iio/devices/trigger1/name             # 可以看到这个trigger
+
+insmod /root/dht11.ko
+cd /sys/bus/iio/devices/iio\:device2/
+echo timer_abc > trigger/current_trigger               # 在设备上使用trigger
+
+echo 30 > events/in_temp_thresh_rising_value   # 设置上限报警值
+echo 10 > events/in_temp_thresh_falling_value  # 设置下限报警值
+echo 1 > events/in_temp_thresh_either_en       # 使能event
+
+echo 1 > scan_elements/in_humidityrelative_en
+echo 1 > scan_elements/in_temp_en
+echo 1 > buffer/enable
+
+# hexdump /dev/iio\:device2
+/root/dht11_test /dev/iio\:device2  # 读取事件
+```
+
+
+
+#### 1.3.2 STM32MP157
+
+```SHELL
+# insmod /root/iio-trig-hrtimer.ko # 157上已经有了这个驱动
+mkdir  /sys/kernel/config/iio/triggers/hrtimer/timer_abc  # 创建trigger
+cat /sys/bus/iio/devices/trigger1/name             # 可以看到这个trigger
+
+insmod /root/dht11.ko
+cd /sys/bus/iio/devices/iio\:device1/
+echo timer_abc > trigger/current_trigger               # 在设备上使用trigger
+
+echo 30 > events/in_temp_thresh_rising_value   # 设置上限报警值
+echo 10 > events/in_temp_thresh_falling_value  # 设置下限报警值
+echo 1 > events/in_temp_thresh_either_en       # 使能event
+
+echo 1 > scan_elements/in_humidityrelative_en
+echo 1 > scan_elements/in_temp_en
+echo 1 > buffer/enable
+
+# hexdump /dev/iio\:device1
+/root/dht11_test /dev/iio\:device1  # 读取事件
+```
+
+
+
+## 4. 使用trigger写iio_event(不实用)
+
+IMX6ULL的源码：
+
+![image-20241126094637080](pic/image-20241126094637080.png)
+
+STM32MP157的源码：
+
+![image-20241126094715687](pic/image-20241126094715687.png)
+
+### 4.1 框图
+
+下图中，左侧写kfifo的红色线条，就是使用trigger写iio_event：
+
+![image-20241125161222685](pic/image-20241125161222685.png)
+
+
+
+### 4.2 提供虚拟中断处理函数
+
+![image-20241127103153056](pic/image-20241127103153056.png)
+
+
+
+### 4.3 注册虚拟中断处理函数
+
+设置iio_device的trgger，比如如下操作：
+
+```shell
+insmod /root/iio-trig-hrtimer.ko
+mkdir  /sys/kernel/config/iio/triggers/hrtimer/timer_abc  # 创建trigger
+cat /sys/bus/iio/devices/trigger1/name             # 可以看到这个trigger
+
+insmod /root/dht11.ko
+cd /sys/bus/iio/devices/iio\:device2/
+echo timer_abc > trigger/current_trigger               # 在设备上使用trigger
+```
+
+会导致如下函数被调用，它就注册了"记录在pollfunc_event里的"虚拟中断函数：
+
+![image-20241127103523330](pic/image-20241127103523330.png)
+
+
+
+注意，对比一下：
+
+* "记录在pollfunc_event里的"虚拟中断函数：
+  * 在设置iio设备的current_trigger时就注册了中断, 就会使能trigger state
+  * 用来产生iio_event，写KFIFO
+* "记录在pollfunc里的"虚拟中断函数：
+  * 在设置iio设备的current_trigger后、并且使能了buffer，才注册中断, 就会使能trigger state
+  * 用来读取传感器数据，写iio_buffer
+
+### 4.4 上机体验
+
+#### 4.4.1 修改内核支持
+
+![image-20241127104547343](pic/image-20241127104547343.png)
+
+
+
+#### 4.4.2 具体操作
+
+IMX6ULL:
+
+```shell
+insmod /root/iio-trig-hrtimer.ko
+mkdir  /sys/kernel/config/iio/triggers/hrtimer/timer_abc  # 创建trigger
+cat /sys/bus/iio/devices/trigger1/name             # 可以看到这个trigger
+
+insmod /root/industrialio-triggered-event.ko
+
+insmod /root/dht11.ko
+cd /sys/bus/iio/devices/iio\:device2/
+echo timer_abc > trigger/current_trigger               # 在设备上使用trigger
+
+echo 30 > events/in_temp_thresh_rising_value   # 设置上限报警值
+echo 10 > events/in_temp_thresh_falling_value  # 设置下限报警值
+echo 1 > events/in_temp_thresh_either_en       # 使能event
+
+echo 1 > scan_elements/in_humidityrelative_en
+echo 1 > scan_elements/in_temp_en
+echo 1 > buffer/enable
+
+# hexdump /dev/iio\:device2
+/root/dht11_test /dev/iio\:device2  # 读取事件
+```
+
+
+
+STM32MP157:
+
+```shell
+# insmod /root/iio-trig-hrtimer.ko # 157上已经有了这个驱动
+mkdir  /sys/kernel/config/iio/triggers/hrtimer/timer_abc  # 创建trigger
+cat /sys/bus/iio/devices/trigger1/name             # 可以看到这个trigger
+
+insmod /root/industrialio-triggered-event.ko
+
+insmod /root/dht11.ko
+cd /sys/bus/iio/devices/iio\:device1/
+echo timer_abc > trigger/current_trigger               # 在设备上使用trigger
+
+echo 30 > events/in_temp_thresh_rising_value   # 设置上限报警值
+echo 10 > events/in_temp_thresh_falling_value  # 设置下限报警值
+echo 1 > events/in_temp_thresh_either_en       # 使能event
+
+echo 1 > scan_elements/in_humidityrelative_en
+echo 1 > scan_elements/in_temp_en
+echo 1 > buffer/enable
+
+# hexdump /dev/iio\:device1
+/root/dht11_test /dev/iio\:device1  # 读取事件
+```
+

STM32MP157/doc_pic/14_IIO/05_iio驱动示例.md

@@ -0,0 +1,217 @@
+# iio驱动示例
+
+IIO(Industrial I/O)参考资料：
+
+* 系列文章：https://blog.csdn.net/lickylin/article/details/108177756
+* https://www.cnblogs.com/yongleili717/p/10758691.html
+* 内核文档：https://www.kernel.org/doc/html/v5.3/driver-api/iio
+* 参考内核源码
+  * IMX6ULL: `drivers\iio\adc\vf610_adc.c`
+  * STM32MP157: `drivers\iio\adc\stm32-adc-core.c`，`drivers\iio\adc\stm32-adc.c`
+
+
+
+## 1. IMX6ULL ADC驱动
+
+### 1.1 设备树
+
+![image-20241127131900125](pic/image-20241127131900125.png)
+
+
+
+### 1.2 驱动程序
+
+![image-20241127132025400](pic/image-20241127132025400.png)
+
+
+
+### 1.3 驱动程序分析
+
+```shell
+static int vf610_read_raw(struct iio_dev *indio_dev,
+			struct iio_chan_spec const *chan,
+			int *val,
+			int *val2,
+			long mask)
+
+怎么使用val, val2 ?
+
+IIO_VAL_INT : 只有整数没有小数, 整数保存在val里，val2不使用。
+IIO_VAL_INT_PLUS_MICRO : val=整数，val2=小数部分*1000000，比如3.14如此保存：*val = 3; *val2 = 140000
+IIO_VAL_INT_PLUS_NANO  : val=整数，val2=小数部分*1000000000，比如3.14如此保存：*val = 3; *val2 = 140000000
+IIO_VAL_INT_PLUS_MICRO_DB : DB数据，数值的表示方法跟IIO_VAL_INT_PLUS_MICRO一样，添加了单位DB。
+IIO_VAL_INT_MULTIPLE : 返回多个整数值，主要用于iio_info的read_raw_multi函数。
+IIO_VAL_FRACTIONAL   : 分数，比如n/m，表示为：*val=n, *val2=m
+IIO_VAL_FRACTIONAL_LOG2 : LOG2值, 比如*val=1，*val2=4，表示的数值为：val>>val2, 即1>>4=0.03125
+```
+
+
+
+### 1.4 驱动程序使用
+
+#### 1.4.1 各类值的含义
+
+![image-20241127132345881](pic/image-20241127132345881.png)
+
+#### 1.4.2 示例
+
+IMX6ULL原理图：
+
+![image-20241127132457129](pic/image-20241127132457129.png)
+
+可以通过扩展板引出，原理图如下：
+
+![image-20241127132553738](pic/image-20241127132553738.png)
+
+
+
+测试时接线方法：可以把ADC1_CH3或ADC1_CH4，接到3V3或GND，如下图：
+
+![image-20241127145118931](pic/image-20241127145118931.png)
+
+
+
+操作命令：
+
+```shell
+# 单步操作
+cd /sys/bus/iio/devices/iio:device0  
+cat in_voltage3_raw
+
+# 使用buffer
+insmod /root/iio-trig-hrtimer.ko
+mkdir  /sys/kernel/config/iio/triggers/hrtimer/timer_abc  # 创建trigger
+cat /sys/bus/iio/devices/trigger1/name             # 可以看到这个trigger
+# 设置trigger周期
+cd /sys/bus/iio/devices/trigger1
+echo 1000000000 > sampling_frequency  # 单位ns, 1s一次
+
+cd /sys/bus/iio/devices/iio\:device0/
+echo timer_abc > trigger/current_trigger               # 在设备上使用trigger
+
+echo 1 > scan_elements/in_voltage3_en
+echo 1024 > buffer/length
+echo 1 > buffer/enable
+
+# hexdump /dev/iio\:device1
+hexdump /dev/iio\:device0  # 读取数据
+```
+
+
+
+注意：使用buffer功能会死机，原因未明。
+
+
+
+
+
+## 2. STM32MP157 ADC驱动
+
+### 2.1 设备树与驱动
+
+如何确定设备树与驱动？百问网STM32MP157开发板使用的设备树文件是`stm32mp157c-100ask-512d-lcd-v1.dtb`，可以在Ubuntu使用如下命令反汇编得到dts文件：
+
+```shell
+dtc -I dtb -O dts stm32mp157c-100ask-512d-lcd-v1.dtb > 1.dts
+```
+
+在1.dts中搜`adc`，可以看到如下节点，根据里面的`compatible`属性即可找到设备树和驱动：
+
+![image-20241128095523369](pic/image-20241128095523369.png)
+
+
+
+#### 2.1.1 设备树文件
+
+![image-20241128095902459](pic/image-20241128095902459.png)
+
+#### 2.1.2 驱动文件
+
+`drivers\iio\adc\stm32-adc-core.c`，`drivers\iio\adc\stm32-adc.c`
+
+
+
+### 2.2 为何驱动程序无法使用
+
+#### 2.2.1 pinmux空缺
+
+查看内核打印信息：
+
+```shell
+[    4.112842] stm32mp157-pinctrl soc:pin-controller@50002000: missing pins property in node pins .
+[    4.120360] stm32-adc-core: probe of 48003000.adc failed with error -22
+
+```
+
+根据错误信息"missing pins property in node"，找到驱动：pinctrl/stm32/pinctrl-stm32.c
+
+![image-20241128105620144](pic/image-20241128105620144.png)
+
+在设备树里确实发现ADC使用的pinctrl里没有"pinmux"属性：
+
+![image-20241128105502688](pic/image-20241128105502688.png)
+
+
+
+如此修改：
+
+![image-20241128131324394](pic/image-20241128131324394.png)
+
+
+
+#### 2.2.2 提供regulator
+
+![image-20241128132450046](pic/image-20241128132450046.png)
+
+
+
+### 2.3 上机实验
+
+#### 2.3.1 原理图与接线
+
+STM32MP157原理图：
+
+![image-20241128133548599](pic/image-20241128133548599.png)
+
+扩展板原理图：
+
+![image-20241128133617577](pic/image-20241128133617577.png)
+
+
+
+接线方法：
+
+![image-20241128133856564](pic/image-20241128133856564.png)
+
+
+
+#### 2.3.2 测试命令
+
+```shell
+# 单步操作
+cd /sys/bus/iio/devices/iio:device1  
+cat in_voltage0_raw
+
+# 使用buffer
+# insmod /root/iio-trig-hrtimer.ko  # STM32MMP157无需安装驱动
+mkdir  /sys/kernel/config/iio/triggers/hrtimer/timer_abc  # 创建trigger
+cat /sys/bus/iio/devices/trigger1/name             # 可以看到这个trigger
+# 设置trigger周期
+cd /sys/bus/iio/devices/trigger1
+echo 1000000000 > sampling_frequency  # 单位ns, 1s一次
+
+cd /sys/bus/iio/devices/iio\:device1/
+echo timer_abc > trigger/current_trigger               # 在设备上使用trigger
+
+echo 1 > scan_elements/in_voltage0_en
+echo 1024 > buffer/length
+echo 1 > buffer/enable
+
+# hexdump /dev/iio\:device1
+hexdump /dev/iio\:device1  # 读取数据
+```
+
+
+
+### 2.4 驱动程序分析
+

STM32MP157/source/A7/14_iio/05_dht11_iio_event/dht11.c

@@ -0,0 +1,664 @@
+/*
+ * DHT11/DHT22 bit banging GPIO driver
+ *
+ * Copyright (c) Harald Geyer <harald@ccbib.org>
+ */
+
+#include <linux/err.h>
+#include <linux/interrupt.h>
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/printk.h>
+#include <linux/slab.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/sysfs.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/wait.h>
+#include <linux/bitops.h>
+#include <linux/completion.h>
+#include <linux/mutex.h>
+#include <linux/delay.h>
+#include <linux/gpio/consumer.h>
+#include <linux/timekeeping.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/kfifo_buf.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/iio/triggered_buffer.h>
+#include <linux/iio/events.h>
+#include <linux/iio/triggered_event.h>
+
+#define DRIVER_NAME	"dht11"
+
+#define DHT11_DATA_VALID_TIME	2000000000  /* 2s in ns */
+
+#define DHT11_EDGES_PREAMBLE 2
+#define DHT11_BITS_PER_READ 40
+/*
+ * Note that when reading the sensor actually 84 edges are detected, but
+ * since the last edge is not significant, we only store 83:
+ */
+#define DHT11_EDGES_PER_READ (2 * DHT11_BITS_PER_READ + \
+			      DHT11_EDGES_PREAMBLE + 1)
+
+/*
+ * Data transmission timing:
+ * Data bits are encoded as pulse length (high time) on the data line.
+ * 0-bit: 22-30uS -- typically 26uS (AM2302)
+ * 1-bit: 68-75uS -- typically 70uS (AM2302)
+ * The acutal timings also depend on the properties of the cable, with
+ * longer cables typically making pulses shorter.
+ *
+ * Our decoding depends on the time resolution of the system:
+ * timeres > 34uS ... don't know what a 1-tick pulse is
+ * 34uS > timeres > 30uS ... no problem (30kHz and 32kHz clocks)
+ * 30uS > timeres > 23uS ... don't know what a 2-tick pulse is
+ * timeres < 23uS ... no problem
+ *
+ * Luckily clocks in the 33-44kHz range are quite uncommon, so we can
+ * support most systems if the threshold for decoding a pulse as 1-bit
+ * is chosen carefully. If somebody really wants to support clocks around
+ * 40kHz, where this driver is most unreliable, there are two options.
+ * a) select an implementation using busy loop polling on those systems
+ * b) use the checksum to do some probabilistic decoding
+ */
+#define DHT11_START_TRANSMISSION_MIN	18000  /* us */
+#define DHT11_START_TRANSMISSION_MAX	20000  /* us */
+#define DHT11_MIN_TIMERES	34000  /* ns */
+#define DHT11_THRESHOLD		49000  /* ns */
+#define DHT11_AMBIG_LOW		23000  /* ns */
+#define DHT11_AMBIG_HIGH	30000  /* ns */
+
+struct dht11 {
+	struct device			*dev;
+
+	struct gpio_desc		*gpiod;
+	int				irq;
+
+	struct completion		completion;
+	/* The iio sysfs interface doesn't prevent concurrent reads: */
+	struct mutex			lock;
+
+	s64				timestamp;
+	int				temperature;
+	int				humidity;
+
+	/* num_edges: -1 means "no transmission in progress" */
+	int				num_edges;
+	struct {s64 ts; int value; }	edges[DHT11_EDGES_PER_READ];
+	struct delayed_work		work;
+	struct iio_dev *iio;
+};
+
+#ifdef CONFIG_DYNAMIC_DEBUG
+/*
+ * dht11_edges_print: show the data as actually received by the
+ *                    driver.
+ */
+static void dht11_edges_print(struct dht11 *dht11)
+{
+	int i;
+
+	dev_dbg(dht11->dev, "%d edges detected:\n", dht11->num_edges);
+	for (i = 1; i < dht11->num_edges; ++i) {
+		dev_dbg(dht11->dev, "%d: %lld ns %s\n", i,
+			dht11->edges[i].ts - dht11->edges[i - 1].ts,
+			dht11->edges[i - 1].value ? "high" : "low");
+	}
+}
+#endif /* CONFIG_DYNAMIC_DEBUG */
+
+static unsigned char dht11_decode_byte(char *bits)
+{
+	unsigned char ret = 0;
+	int i;
+
+	for (i = 0; i < 8; ++i) {
+		ret <<= 1;
+		if (bits[i])
+			++ret;
+	}
+
+	return ret;
+}
+
+static int dht11_decode(struct dht11 *dht11, int offset)
+{
+	int i, t;
+	char bits[DHT11_BITS_PER_READ];
+	unsigned char temp_int, temp_dec, hum_int, hum_dec, checksum;
+
+	for (i = 0; i < DHT11_BITS_PER_READ; ++i) {
+		t = dht11->edges[offset + 2 * i + 2].ts -
+			dht11->edges[offset + 2 * i + 1].ts;
+		if (!dht11->edges[offset + 2 * i + 1].value) {
+			dev_dbg(dht11->dev,
+				"lost synchronisation at edge %d\n",
+				offset + 2 * i + 1);
+			return -EIO;
+		}
+		bits[i] = t > DHT11_THRESHOLD;
+	}
+
+	hum_int = dht11_decode_byte(bits);
+	hum_dec = dht11_decode_byte(&bits[8]);
+	temp_int = dht11_decode_byte(&bits[16]);
+	temp_dec = dht11_decode_byte(&bits[24]);
+	checksum = dht11_decode_byte(&bits[32]);
+
+	if (((hum_int + hum_dec + temp_int + temp_dec) & 0xff) != checksum) {
+		dev_dbg(dht11->dev, "invalid checksum\n");
+		return -EIO;
+	}
+
+	dht11->timestamp = ktime_get_boottime_ns();
+	if (hum_int < 4) {  /* DHT22: 100000 = (3*256+232)*100 */
+		dht11->temperature = (((temp_int & 0x7f) << 8) + temp_dec) *
+					((temp_int & 0x80) ? -100 : 100);
+		dht11->humidity = ((hum_int << 8) + hum_dec) * 100;
+	} else  {
+		dht11->temperature = temp_int;
+		dht11->humidity = hum_int;
+	}
+
+	return 0;
+}
+
+/*
+ * IRQ handler called on GPIO edges
+ */
+static irqreturn_t dht11_handle_irq(int irq, void *data)
+{
+	struct iio_dev *iio = data;
+	struct dht11 *dht11 = iio_priv(iio);
+
+	/* TODO: Consider making the handler safe for IRQ sharing */
+	if (dht11->num_edges < DHT11_EDGES_PER_READ && dht11->num_edges >= 0) {
+		dht11->edges[dht11->num_edges].ts = ktime_get_boottime_ns();
+		dht11->edges[dht11->num_edges++].value =
+						gpiod_get_value(dht11->gpiod);
+
+		if (dht11->num_edges >= DHT11_EDGES_PER_READ)
+			complete(&dht11->completion);
+	}
+
+	return IRQ_HANDLED;
+}
+
+static int dht11_read_raw(struct iio_dev *iio_dev,
+			  const struct iio_chan_spec *chan,
+			int *val, int *val2, long m)
+{
+	struct dht11 *dht11 = iio_priv(iio_dev);
+	int ret, timeres, offset;
+
+	mutex_lock(&dht11->lock);
+	if (dht11->timestamp + DHT11_DATA_VALID_TIME < ktime_get_boottime_ns()) {
+		timeres = ktime_get_resolution_ns();
+		dev_dbg(dht11->dev, "current timeresolution: %dns\n", timeres);
+		if (timeres > DHT11_MIN_TIMERES) {
+			dev_err(dht11->dev, "timeresolution %dns too low\n",
+				timeres);
+			/* In theory a better clock could become available
+			 * at some point ... and there is no error code
+			 * that really fits better.
+			 */
+			ret = -EAGAIN;
+			goto err;
+		}
+		if (timeres > DHT11_AMBIG_LOW && timeres < DHT11_AMBIG_HIGH)
+			dev_warn(dht11->dev,
+				 "timeresolution: %dns - decoding ambiguous\n",
+				 timeres);
+
+		reinit_completion(&dht11->completion);
+
+		dht11->num_edges = 0;
+		ret = gpiod_direction_output(dht11->gpiod, 0);
+		if (ret)
+			goto err;
+		usleep_range(DHT11_START_TRANSMISSION_MIN,
+			     DHT11_START_TRANSMISSION_MAX);
+		ret = gpiod_direction_input(dht11->gpiod);
+		if (ret)
+			goto err;
+
+		ret = request_irq(dht11->irq, dht11_handle_irq,
+				  IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
+				  iio_dev->name, iio_dev);
+		if (ret)
+			goto err;
+
+		ret = wait_for_completion_killable_timeout(&dht11->completion,
+							   HZ);
+
+		free_irq(dht11->irq, iio_dev);
+
+#ifdef CONFIG_DYNAMIC_DEBUG
+		dht11_edges_print(dht11);
+#endif
+
+		if (ret == 0 && dht11->num_edges < DHT11_EDGES_PER_READ - 1) {
+			dev_err(dht11->dev, "Only %d signal edges detected\n",
+				dht11->num_edges);
+			ret = -ETIMEDOUT;
+		}
+		if (ret < 0)
+			goto err;
+
+		offset = DHT11_EDGES_PREAMBLE +
+				dht11->num_edges - DHT11_EDGES_PER_READ;
+		for (; offset >= 0; --offset) {
+			ret = dht11_decode(dht11, offset);
+			if (!ret)
+				break;
+		}
+
+		if (ret)
+			goto err;
+	}
+
+	ret = IIO_VAL_INT;
+	if (chan->type == IIO_TEMP)
+		*val = dht11->temperature;
+	else if (chan->type == IIO_HUMIDITYRELATIVE)
+		*val = dht11->humidity;
+	else
+		ret = -EINVAL;
+err:
+	dht11->num_edges = -1;
+	mutex_unlock(&dht11->lock);
+	return ret;
+}
+
+static const struct iio_info dht11_iio_info = {
+	.read_raw		= dht11_read_raw,
+};
+
+static const struct iio_event_spec dht11_temp_events[] = {
+	{
+		.type = IIO_EV_TYPE_THRESH,
+		.dir = IIO_EV_DIR_RISING,
+		.mask_separate = BIT(IIO_EV_INFO_VALUE),
+	}, {
+		.type = IIO_EV_TYPE_THRESH,
+		.dir = IIO_EV_DIR_FALLING,
+		.mask_separate = BIT(IIO_EV_INFO_VALUE),
+	}, {
+		.type = IIO_EV_TYPE_THRESH,
+		.dir = IIO_EV_DIR_EITHER,
+		.mask_separate = BIT(IIO_EV_INFO_ENABLE),
+	},
+};
+
+static const struct iio_chan_spec dht11_chan_spec[] = {
+	{ .type = IIO_TEMP,
+		.scan_index = 0,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), 
+		.scan_type = {
+			.sign = 's',
+			.realbits = 8,
+			.storagebits = 8,
+		},
+		.event_spec = dht11_temp_events,
+		.num_event_specs = ARRAY_SIZE(dht11_temp_events),		
+	},
+	{ .type = IIO_HUMIDITYRELATIVE,
+		.scan_index = 1,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), 
+		.scan_type = {
+			.sign = 's',
+			.realbits = 8,
+			.storagebits = 8,
+		},
+	}
+};
+
+static const struct of_device_id dht11_dt_ids[] = {
+	{ .compatible = "dht11", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, dht11_dt_ids);
+
+static int dht11_buf_preenable(struct iio_dev *indio_dev)
+{
+	return 0;
+}
+
+static int dht11_buf_postenable(struct iio_dev *indio_dev)
+{
+	struct dht11 *dht11 = iio_priv(indio_dev);
+	
+	/* start work */
+	schedule_delayed_work(&dht11->work, 1);
+	
+	return 0;
+}
+
+static int dht11_buf_postdisable(struct iio_dev *indio_dev)
+{
+	struct dht11 *dht11 = iio_priv(indio_dev);
+
+	/* cancel work */
+	cancel_delayed_work_sync(&dht11->work);
+	return 0;
+}
+
+
+static const struct iio_buffer_setup_ops dht11_buf_setup_ops = {
+	.preenable = dht11_buf_preenable,
+	.postenable = dht11_buf_postenable,
+	.postdisable = dht11_buf_postdisable,
+};
+
+static irqreturn_t dht11_triggered_buf_handle(int irq, void * p)
+{
+	struct iio_poll_func *pf = p;
+	pf->timestamp = iio_get_time_ns(pf->indio_dev);
+	return IRQ_WAKE_THREAD;
+}
+
+static irqreturn_t dht11_triggered_buf_thread(int irq, void * p)
+{
+	/* read data */
+	struct iio_poll_func *pf = p;
+	struct iio_dev *iio_dev = pf->indio_dev;	
+	struct dht11 *dht11 = iio_priv(iio_dev);
+	
+	int ret, timeres, offset;
+	uint8_t vals[2];
+	
+	/* read dht11 */
+	mutex_lock(&dht11->lock);
+	if (dht11->timestamp + DHT11_DATA_VALID_TIME < ktime_get_boottime_ns()) {
+		timeres = ktime_get_resolution_ns();
+		dev_dbg(dht11->dev, "current timeresolution: %dns\n", timeres);
+		if (timeres > DHT11_MIN_TIMERES) {
+			dev_err(dht11->dev, "timeresolution %dns too low\n",
+				timeres);
+			/* In theory a better clock could become available
+			 * at some point ... and there is no error code
+			 * that really fits better.
+			 */
+			ret = -EAGAIN;
+			goto err;
+		}
+		if (timeres > DHT11_AMBIG_LOW && timeres < DHT11_AMBIG_HIGH)
+			dev_warn(dht11->dev,
+				 "timeresolution: %dns - decoding ambiguous\n",
+				 timeres);
+
+		reinit_completion(&dht11->completion);
+
+		dht11->num_edges = 0;
+		ret = gpiod_direction_output(dht11->gpiod, 0);
+		if (ret)
+			goto err;
+		usleep_range(DHT11_START_TRANSMISSION_MIN,
+				 DHT11_START_TRANSMISSION_MAX);
+		ret = gpiod_direction_input(dht11->gpiod);
+		if (ret)
+			goto err;
+
+		ret = request_irq(dht11->irq, dht11_handle_irq,
+				  IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
+				  iio_dev->name, iio_dev);
+		if (ret)
+			goto err;
+
+		ret = wait_for_completion_killable_timeout(&dht11->completion,
+							   HZ);
+
+		free_irq(dht11->irq, iio_dev);
+
+#ifdef CONFIG_DYNAMIC_DEBUG
+		dht11_edges_print(dht11);
+#endif
+
+		if (ret == 0 && dht11->num_edges < DHT11_EDGES_PER_READ - 1) {
+			dev_err(dht11->dev, "Only %d signal edges detected\n",
+				dht11->num_edges);
+			ret = -ETIMEDOUT;
+		}
+		if (ret < 0)
+			goto err;
+
+		offset = DHT11_EDGES_PREAMBLE +
+				dht11->num_edges - DHT11_EDGES_PER_READ;
+		for (; offset >= 0; --offset) {
+			ret = dht11_decode(dht11, offset);
+			if (!ret)
+				break;
+		}
+
+		if (ret)
+			goto err;
+	}
+
+	vals[0] = dht11->temperature;
+	vals[1] = dht11->humidity;
+	
+	/* put data into iio_buffer */
+	iio_push_to_buffers(iio_dev, vals);
+
+	if (vals[0] > 30)
+	{
+		iio_push_event(iio_dev,
+				   IIO_UNMOD_EVENT_CODE(IIO_TEMP, 0,
+						IIO_EV_TYPE_THRESH, IIO_EV_DIR_RISING),
+				   iio_get_time_ns(iio_dev));
+	}
+		
+err:
+	dht11->num_edges = -1;
+	mutex_unlock(&dht11->lock);
+
+	iio_trigger_notify_done(iio_dev->trig);
+
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t dht11_event_handler(int irq, void *private)
+{
+	struct iio_poll_func *pf = private;
+	struct iio_dev *idev = pf->indio_dev;
+
+	iio_push_event(idev,
+			   IIO_UNMOD_EVENT_CODE(IIO_TEMP, 0,
+					IIO_EV_TYPE_THRESH, IIO_EV_DIR_RISING),
+			   iio_get_time_ns(idev));
+
+	iio_trigger_notify_done(idev->trig);
+
+	return IRQ_HANDLED;
+}
+
+static int dht11_buffer_init(struct iio_dev *indio_dev)
+{
+#if 0
+	struct iio_buffer *buffer;
+
+	buffer = iio_kfifo_allocate();
+	if (!buffer)
+		return -ENOMEM;
+
+	iio_device_attach_buffer(indio_dev, buffer);
+
+	/* Ring buffer functions - here trigger setup related */
+	indio_dev->setup_ops = &dht11_buf_setup_ops;
+
+	return 0;
+#else
+	//int ret = iio_triggered_event_setup(indio_dev, NULL, dht11_event_handler);
+	//if (ret)
+	//	return ret;
+	
+	return iio_triggered_buffer_setup(indio_dev, dht11_triggered_buf_handle, dht11_triggered_buf_thread, NULL);
+#endif	
+}
+
+static void dht11_work(struct work_struct *work)
+{
+	struct dht11 *dht11 = container_of(work, struct dht11, work.work);
+	int ret, timeres, offset;
+	struct iio_dev *iio_dev = dht11->iio;
+	uint8_t vals[2];
+	
+	/* read dht11 */
+	mutex_lock(&dht11->lock);
+	if (dht11->timestamp + DHT11_DATA_VALID_TIME < ktime_get_boottime_ns()) {
+		timeres = ktime_get_resolution_ns();
+		dev_dbg(dht11->dev, "current timeresolution: %dns\n", timeres);
+		if (timeres > DHT11_MIN_TIMERES) {
+			dev_err(dht11->dev, "timeresolution %dns too low\n",
+				timeres);
+			/* In theory a better clock could become available
+			 * at some point ... and there is no error code
+			 * that really fits better.
+			 */
+			ret = -EAGAIN;
+			goto err;
+		}
+		if (timeres > DHT11_AMBIG_LOW && timeres < DHT11_AMBIG_HIGH)
+			dev_warn(dht11->dev,
+				 "timeresolution: %dns - decoding ambiguous\n",
+				 timeres);
+
+		reinit_completion(&dht11->completion);
+
+		dht11->num_edges = 0;
+		ret = gpiod_direction_output(dht11->gpiod, 0);
+		if (ret)
+			goto err;
+		usleep_range(DHT11_START_TRANSMISSION_MIN,
+			     DHT11_START_TRANSMISSION_MAX);
+		ret = gpiod_direction_input(dht11->gpiod);
+		if (ret)
+			goto err;
+
+		ret = request_irq(dht11->irq, dht11_handle_irq,
+				  IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
+				  iio_dev->name, iio_dev);
+		if (ret)
+			goto err;
+
+		ret = wait_for_completion_killable_timeout(&dht11->completion,
+							   HZ);
+
+		free_irq(dht11->irq, iio_dev);
+
+#ifdef CONFIG_DYNAMIC_DEBUG
+		dht11_edges_print(dht11);
+#endif
+
+		if (ret == 0 && dht11->num_edges < DHT11_EDGES_PER_READ - 1) {
+			dev_err(dht11->dev, "Only %d signal edges detected\n",
+				dht11->num_edges);
+			ret = -ETIMEDOUT;
+		}
+		if (ret < 0)
+			goto err;
+
+		offset = DHT11_EDGES_PREAMBLE +
+				dht11->num_edges - DHT11_EDGES_PER_READ;
+		for (; offset >= 0; --offset) {
+			ret = dht11_decode(dht11, offset);
+			if (!ret)
+				break;
+		}
+
+		if (ret)
+			goto err;
+	}
+
+	vals[0] = dht11->temperature;
+	vals[1] = dht11->humidity;
+	
+	/* put data into iio_buffer */
+	iio_push_to_buffers(iio_dev, vals);
+	
+err:
+	dht11->num_edges = -1;
+	mutex_unlock(&dht11->lock);
+	
+	/* re-start work */
+	if (ret)
+	{
+		/* 有错误 */
+		schedule_delayed_work(&dht11->work, 0);
+	}
+	else
+	{
+		schedule_delayed_work(&dht11->work, HZ);
+	}
+}
+
+static const unsigned long dht11_scan_masks[] = {0x3, 0};
+
+static int dht11_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct dht11 *dht11;
+	struct iio_dev *iio;
+
+	iio = devm_iio_device_alloc(dev, sizeof(*dht11));
+	if (!iio) {
+		dev_err(dev, "Failed to allocate IIO device\n");
+		return -ENOMEM;
+	}
+
+	dht11 = iio_priv(iio);
+	dht11->dev = dev;
+	dht11->iio = iio;
+
+	dht11->gpiod = devm_gpiod_get(dev, NULL, GPIOD_IN);
+	if (IS_ERR(dht11->gpiod))
+		return PTR_ERR(dht11->gpiod);
+
+
+	dht11->irq = gpiod_to_irq(dht11->gpiod);
+	if (dht11->irq < 0) {
+		dev_err(dev, "GPIO %d has no interrupt\n", desc_to_gpio(dht11->gpiod));
+		return -EINVAL;
+	}
+
+	dht11->timestamp = ktime_get_boottime_ns() - DHT11_DATA_VALID_TIME - 1;
+	dht11->num_edges = -1;
+
+	platform_set_drvdata(pdev, iio);
+
+	init_completion(&dht11->completion);
+	mutex_init(&dht11->lock);
+	iio->name = pdev->name;
+	iio->dev.parent = &pdev->dev;
+	iio->info = &dht11_iio_info;
+	iio->modes = INDIO_DIRECT_MODE | INDIO_BUFFER_SOFTWARE;
+	iio->channels = dht11_chan_spec;
+	iio->num_channels = ARRAY_SIZE(dht11_chan_spec);
+	iio->available_scan_masks = dht11_scan_masks;
+
+	dht11_buffer_init(iio);
+
+	/* init work */
+	INIT_DELAYED_WORK(&dht11->work, dht11_work);
+
+	return devm_iio_device_register(dev, iio);
+}
+
+static struct platform_driver dht11_driver = {
+	.driver = {
+		.name	= DRIVER_NAME,
+		.of_match_table = dht11_dt_ids,
+	},
+	.probe  = dht11_probe,
+};
+
+module_platform_driver(dht11_driver);
+
+MODULE_AUTHOR("Harald Geyer <harald@ccbib.org>");
+MODULE_DESCRIPTION("DHT11 humidity/temperature sensor driver");
+MODULE_LICENSE("GPL v2");

STM32MP157/source/A7/14_iio/05_dht11_iio_event/dht11.dts

@@ -0,0 +1,4 @@
+humidity_sensor {
+	compatible = "dht11";
+    gpios = <&gpioa 5 GPIO_ACTIVE_HIGH>;
+};

STM32MP157/source/A7/14_iio/05_dht11_iio_event/dht11_test.c

@@ -0,0 +1,50 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <string.h>
+
+#include <sys/ioctl.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include <linux/types.h>
+#include <linux/iio/events.h>
+
+int main(int argc, char **argv)
+{
+	int fd;
+	int ret;
+	int event_fd;
+	struct iio_event_data event;
+	
+	if (argc != 2)
+	{
+		printf("Usage: %s /dev/iio\\:deviceX\n", argv[0]);
+		return 0;
+	}
+
+	fd = open(argv[1], O_RDWR);  // /dev/iio:device2
+	if (fd < 0) {
+		printf("can not open %s\n", argv[1]);
+		return -1;
+	}
+
+	ret = ioctl(fd, IIO_GET_EVENT_FD_IOCTL, &event_fd);
+	if (ret < 0) {
+		printf("can not get event fd\n");
+		return -1;
+	}
+
+	while (1)
+	{
+		ret = read(event_fd, &event, sizeof(event));
+		if (ret == sizeof(event))
+		{
+			printf("Get event: 0x%lx\n", event.id);
+		}
+	}
+
+	return 0;
+}
+

STM32MP157/source/A7/14_iio/06_dht11_iio_event_课堂现场编写/dht11.c

@@ -0,0 +1,746 @@
+/*
+ * DHT11/DHT22 bit banging GPIO driver
+ *
+ * Copyright (c) Harald Geyer <harald@ccbib.org>
+ */
+
+#include <linux/err.h>
+#include <linux/interrupt.h>
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/printk.h>
+#include <linux/slab.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/sysfs.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/wait.h>
+#include <linux/bitops.h>
+#include <linux/completion.h>
+#include <linux/mutex.h>
+#include <linux/delay.h>
+#include <linux/gpio/consumer.h>
+#include <linux/timekeeping.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/kfifo_buf.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/iio/triggered_buffer.h>
+#include <linux/iio/events.h>
+#include <linux/iio/triggered_event.h>
+
+#define DRIVER_NAME	"dht11"
+
+#define DHT11_DATA_VALID_TIME	2000000000  /* 2s in ns */
+
+#define DHT11_EDGES_PREAMBLE 2
+#define DHT11_BITS_PER_READ 40
+/*
+ * Note that when reading the sensor actually 84 edges are detected, but
+ * since the last edge is not significant, we only store 83:
+ */
+#define DHT11_EDGES_PER_READ (2 * DHT11_BITS_PER_READ + \
+			      DHT11_EDGES_PREAMBLE + 1)
+
+/*
+ * Data transmission timing:
+ * Data bits are encoded as pulse length (high time) on the data line.
+ * 0-bit: 22-30uS -- typically 26uS (AM2302)
+ * 1-bit: 68-75uS -- typically 70uS (AM2302)
+ * The acutal timings also depend on the properties of the cable, with
+ * longer cables typically making pulses shorter.
+ *
+ * Our decoding depends on the time resolution of the system:
+ * timeres > 34uS ... don't know what a 1-tick pulse is
+ * 34uS > timeres > 30uS ... no problem (30kHz and 32kHz clocks)
+ * 30uS > timeres > 23uS ... don't know what a 2-tick pulse is
+ * timeres < 23uS ... no problem
+ *
+ * Luckily clocks in the 33-44kHz range are quite uncommon, so we can
+ * support most systems if the threshold for decoding a pulse as 1-bit
+ * is chosen carefully. If somebody really wants to support clocks around
+ * 40kHz, where this driver is most unreliable, there are two options.
+ * a) select an implementation using busy loop polling on those systems
+ * b) use the checksum to do some probabilistic decoding
+ */
+#define DHT11_START_TRANSMISSION_MIN	18000  /* us */
+#define DHT11_START_TRANSMISSION_MAX	20000  /* us */
+#define DHT11_MIN_TIMERES	34000  /* ns */
+#define DHT11_THRESHOLD		49000  /* ns */
+#define DHT11_AMBIG_LOW		23000  /* ns */
+#define DHT11_AMBIG_HIGH	30000  /* ns */
+
+struct dht11 {
+	struct device			*dev;
+
+	struct gpio_desc		*gpiod;
+	int				irq;
+
+	struct completion		completion;
+	/* The iio sysfs interface doesn't prevent concurrent reads: */
+	struct mutex			lock;
+
+	s64				timestamp;
+	int				temperature;
+	int				humidity;
+
+	/* num_edges: -1 means "no transmission in progress" */
+	int				num_edges;
+	struct {s64 ts; int value; }	edges[DHT11_EDGES_PER_READ];
+	struct delayed_work		work;
+	struct iio_dev *iio;
+	int temp_ev_enable;
+	int temp_thres_up;
+	int temp_thres_down;
+};
+
+#ifdef CONFIG_DYNAMIC_DEBUG
+/*
+ * dht11_edges_print: show the data as actually received by the
+ *                    driver.
+ */
+static void dht11_edges_print(struct dht11 *dht11)
+{
+	int i;
+
+	dev_dbg(dht11->dev, "%d edges detected:\n", dht11->num_edges);
+	for (i = 1; i < dht11->num_edges; ++i) {
+		dev_dbg(dht11->dev, "%d: %lld ns %s\n", i,
+			dht11->edges[i].ts - dht11->edges[i - 1].ts,
+			dht11->edges[i - 1].value ? "high" : "low");
+	}
+}
+#endif /* CONFIG_DYNAMIC_DEBUG */
+
+static unsigned char dht11_decode_byte(char *bits)
+{
+	unsigned char ret = 0;
+	int i;
+
+	for (i = 0; i < 8; ++i) {
+		ret <<= 1;
+		if (bits[i])
+			++ret;
+	}
+
+	return ret;
+}
+
+static int dht11_decode(struct dht11 *dht11, int offset)
+{
+	int i, t;
+	char bits[DHT11_BITS_PER_READ];
+	unsigned char temp_int, temp_dec, hum_int, hum_dec, checksum;
+
+	for (i = 0; i < DHT11_BITS_PER_READ; ++i) {
+		t = dht11->edges[offset + 2 * i + 2].ts -
+			dht11->edges[offset + 2 * i + 1].ts;
+		if (!dht11->edges[offset + 2 * i + 1].value) {
+			dev_dbg(dht11->dev,
+				"lost synchronisation at edge %d\n",
+				offset + 2 * i + 1);
+			return -EIO;
+		}
+		bits[i] = t > DHT11_THRESHOLD;
+	}
+
+	hum_int = dht11_decode_byte(bits);
+	hum_dec = dht11_decode_byte(&bits[8]);
+	temp_int = dht11_decode_byte(&bits[16]);
+	temp_dec = dht11_decode_byte(&bits[24]);
+	checksum = dht11_decode_byte(&bits[32]);
+
+	if (((hum_int + hum_dec + temp_int + temp_dec) & 0xff) != checksum) {
+		dev_dbg(dht11->dev, "invalid checksum\n");
+		return -EIO;
+	}
+
+	dht11->timestamp = ktime_get_boottime_ns();
+	if (hum_int < 4) {  /* DHT22: 100000 = (3*256+232)*100 */
+		dht11->temperature = (((temp_int & 0x7f) << 8) + temp_dec) *
+					((temp_int & 0x80) ? -100 : 100);
+		dht11->humidity = ((hum_int << 8) + hum_dec) * 100;
+	} else  {
+		dht11->temperature = temp_int;
+		dht11->humidity = hum_int;
+	}
+
+	return 0;
+}
+
+/*
+ * IRQ handler called on GPIO edges
+ */
+static irqreturn_t dht11_handle_irq(int irq, void *data)
+{
+	struct iio_dev *iio = data;
+	struct dht11 *dht11 = iio_priv(iio);
+
+	/* TODO: Consider making the handler safe for IRQ sharing */
+	if (dht11->num_edges < DHT11_EDGES_PER_READ && dht11->num_edges >= 0) {
+		dht11->edges[dht11->num_edges].ts = ktime_get_boottime_ns();
+		dht11->edges[dht11->num_edges++].value =
+						gpiod_get_value(dht11->gpiod);
+
+		if (dht11->num_edges >= DHT11_EDGES_PER_READ)
+			complete(&dht11->completion);
+	}
+
+	return IRQ_HANDLED;
+}
+
+static int dht11_read_raw(struct iio_dev *iio_dev,
+			  const struct iio_chan_spec *chan,
+			int *val, int *val2, long m)
+{
+	struct dht11 *dht11 = iio_priv(iio_dev);
+	int ret, timeres, offset;
+
+	mutex_lock(&dht11->lock);
+	if (dht11->timestamp + DHT11_DATA_VALID_TIME < ktime_get_boottime_ns()) {
+		timeres = ktime_get_resolution_ns();
+		dev_dbg(dht11->dev, "current timeresolution: %dns\n", timeres);
+		if (timeres > DHT11_MIN_TIMERES) {
+			dev_err(dht11->dev, "timeresolution %dns too low\n",
+				timeres);
+			/* In theory a better clock could become available
+			 * at some point ... and there is no error code
+			 * that really fits better.
+			 */
+			ret = -EAGAIN;
+			goto err;
+		}
+		if (timeres > DHT11_AMBIG_LOW && timeres < DHT11_AMBIG_HIGH)
+			dev_warn(dht11->dev,
+				 "timeresolution: %dns - decoding ambiguous\n",
+				 timeres);
+
+		reinit_completion(&dht11->completion);
+
+		dht11->num_edges = 0;
+		ret = gpiod_direction_output(dht11->gpiod, 0);
+		if (ret)
+			goto err;
+		usleep_range(DHT11_START_TRANSMISSION_MIN,
+			     DHT11_START_TRANSMISSION_MAX);
+		ret = gpiod_direction_input(dht11->gpiod);
+		if (ret)
+			goto err;
+
+		ret = request_irq(dht11->irq, dht11_handle_irq,
+				  IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
+				  iio_dev->name, iio_dev);
+		if (ret)
+			goto err;
+
+		ret = wait_for_completion_killable_timeout(&dht11->completion,
+							   HZ);
+
+		free_irq(dht11->irq, iio_dev);
+
+#ifdef CONFIG_DYNAMIC_DEBUG
+		dht11_edges_print(dht11);
+#endif
+
+		if (ret == 0 && dht11->num_edges < DHT11_EDGES_PER_READ - 1) {
+			dev_err(dht11->dev, "Only %d signal edges detected\n",
+				dht11->num_edges);
+			ret = -ETIMEDOUT;
+		}
+		if (ret < 0)
+			goto err;
+
+		offset = DHT11_EDGES_PREAMBLE +
+				dht11->num_edges - DHT11_EDGES_PER_READ;
+		for (; offset >= 0; --offset) {
+			ret = dht11_decode(dht11, offset);
+			if (!ret)
+				break;
+		}
+
+		if (ret)
+			goto err;
+	}
+
+	ret = IIO_VAL_INT;
+	if (chan->type == IIO_TEMP)
+		*val = dht11->temperature;
+	else if (chan->type == IIO_HUMIDITYRELATIVE)
+		*val = dht11->humidity;
+	else
+		ret = -EINVAL;
+err:
+	dht11->num_edges = -1;
+	mutex_unlock(&dht11->lock);
+	return ret;
+}
+
+static int dht11_read_event_config(struct iio_dev *idev,
+					const struct iio_chan_spec *chan,
+					enum iio_event_type type,
+					enum iio_event_direction dir)
+{
+	struct dht11 *dht11 = iio_priv(idev);
+
+	return !!dht11->temp_ev_enable;
+}
+
+static int dht11_write_event_config(struct iio_dev *idev,
+					 const struct iio_chan_spec *chan,
+					 enum iio_event_type type,
+					 enum iio_event_direction dir, int state)
+{
+	struct dht11 *dht11 = iio_priv(idev);
+
+	dht11->temp_ev_enable = state;
+
+	return 0;
+}
+
+static int dht11_read_event_value(struct iio_dev *idev,
+				   const struct iio_chan_spec *chan,
+				   enum iio_event_type type,
+				   enum iio_event_direction dir,
+				   enum iio_event_info info,
+				   int *val, int *val2)
+{
+	struct dht11 *dht11 = iio_priv(idev);
+
+	if (chan->type == IIO_TEMP)
+	{
+		if (dir == IIO_EV_DIR_FALLING) {
+			*val = dht11->temp_thres_down;
+		} else {
+			*val = dht11->temp_thres_up;
+		}
+	}
+
+	return IIO_VAL_INT;
+}
+
+static int dht11_write_event_value(struct iio_dev *idev,
+					const struct iio_chan_spec *chan,
+					enum iio_event_type type,
+					enum iio_event_direction dir,
+					enum iio_event_info info,
+					int val, int val2)
+{
+	struct dht11 *dht11 = iio_priv(idev);
+
+	if (chan->type == IIO_TEMP)
+	{
+		if (dir == IIO_EV_DIR_FALLING) {
+			dht11->temp_thres_down = val;
+		} else {
+			dht11->temp_thres_up = val;
+		}
+	}
+
+	return IIO_VAL_INT;
+}
+
+static const struct iio_info dht11_iio_info = {
+	.read_raw		= dht11_read_raw,
+	.write_event_value = dht11_write_event_value,
+	.read_event_value  = dht11_read_event_value,
+	.read_event_config = dht11_read_event_config,
+	.write_event_config = dht11_write_event_config,	
+};
+
+static const struct iio_event_spec dht11_temp_events[] = {
+	{
+		.type = IIO_EV_TYPE_THRESH,
+		.dir = IIO_EV_DIR_RISING,
+		.mask_separate = BIT(IIO_EV_INFO_VALUE),
+	}, {
+		.type = IIO_EV_TYPE_THRESH,
+		.dir = IIO_EV_DIR_FALLING,
+		.mask_separate = BIT(IIO_EV_INFO_VALUE),
+	}, {
+		.type = IIO_EV_TYPE_THRESH,
+		.dir = IIO_EV_DIR_EITHER,
+		.mask_separate = BIT(IIO_EV_INFO_ENABLE),
+	},
+};
+
+static const struct iio_chan_spec dht11_chan_spec[] = {
+	{ .type = IIO_TEMP,
+		.scan_index = 0,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), 
+		.scan_type = {
+			.sign = 's',
+			.realbits = 8,
+			.storagebits = 8,
+		},
+		.event_spec = dht11_temp_events,
+		.num_event_specs = ARRAY_SIZE(dht11_temp_events),		
+	},
+	{ .type = IIO_HUMIDITYRELATIVE,
+		.scan_index = 1,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), 
+		.scan_type = {
+			.sign = 's',
+			.realbits = 8,
+			.storagebits = 8,
+		},
+	}
+};
+
+static const struct of_device_id dht11_dt_ids[] = {
+	{ .compatible = "dht11", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, dht11_dt_ids);
+
+static int dht11_buf_preenable(struct iio_dev *indio_dev)
+{
+	return 0;
+}
+
+static int dht11_buf_postenable(struct iio_dev *indio_dev)
+{
+	struct dht11 *dht11 = iio_priv(indio_dev);
+	
+	/* start work */
+	schedule_delayed_work(&dht11->work, 1);
+	
+	return 0;
+}
+
+static int dht11_buf_postdisable(struct iio_dev *indio_dev)
+{
+	struct dht11 *dht11 = iio_priv(indio_dev);
+
+	/* cancel work */
+	cancel_delayed_work_sync(&dht11->work);
+	return 0;
+}
+
+
+static const struct iio_buffer_setup_ops dht11_buf_setup_ops = {
+	.preenable = dht11_buf_preenable,
+	.postenable = dht11_buf_postenable,
+	.postdisable = dht11_buf_postdisable,
+};
+
+static irqreturn_t dht11_triggered_buf_handle(int irq, void * p)
+{
+	struct iio_poll_func *pf = p;
+	pf->timestamp = iio_get_time_ns(pf->indio_dev);
+	return IRQ_WAKE_THREAD;
+}
+
+static irqreturn_t dht11_triggered_buf_thread(int irq, void * p)
+{
+	/* read data */
+	struct iio_poll_func *pf = p;
+	struct iio_dev *iio_dev = pf->indio_dev;	
+	struct dht11 *dht11 = iio_priv(iio_dev);
+	
+	int ret, timeres, offset;
+	uint8_t vals[2];
+	
+	/* read dht11 */
+	mutex_lock(&dht11->lock);
+	if (dht11->timestamp + DHT11_DATA_VALID_TIME < ktime_get_boottime_ns()) {
+		timeres = ktime_get_resolution_ns();
+		dev_dbg(dht11->dev, "current timeresolution: %dns\n", timeres);
+		if (timeres > DHT11_MIN_TIMERES) {
+			dev_err(dht11->dev, "timeresolution %dns too low\n",
+				timeres);
+			/* In theory a better clock could become available
+			 * at some point ... and there is no error code
+			 * that really fits better.
+			 */
+			ret = -EAGAIN;
+			goto err;
+		}
+		if (timeres > DHT11_AMBIG_LOW && timeres < DHT11_AMBIG_HIGH)
+			dev_warn(dht11->dev,
+				 "timeresolution: %dns - decoding ambiguous\n",
+				 timeres);
+
+		reinit_completion(&dht11->completion);
+
+		dht11->num_edges = 0;
+		ret = gpiod_direction_output(dht11->gpiod, 0);
+		if (ret)
+			goto err;
+		usleep_range(DHT11_START_TRANSMISSION_MIN,
+				 DHT11_START_TRANSMISSION_MAX);
+		ret = gpiod_direction_input(dht11->gpiod);
+		if (ret)
+			goto err;
+
+		ret = request_irq(dht11->irq, dht11_handle_irq,
+				  IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
+				  iio_dev->name, iio_dev);
+		if (ret)
+			goto err;
+
+		ret = wait_for_completion_killable_timeout(&dht11->completion,
+							   HZ);
+
+		free_irq(dht11->irq, iio_dev);
+
+#ifdef CONFIG_DYNAMIC_DEBUG
+		dht11_edges_print(dht11);
+#endif
+
+		if (ret == 0 && dht11->num_edges < DHT11_EDGES_PER_READ - 1) {
+			dev_err(dht11->dev, "Only %d signal edges detected\n",
+				dht11->num_edges);
+			ret = -ETIMEDOUT;
+		}
+		if (ret < 0)
+			goto err;
+
+		offset = DHT11_EDGES_PREAMBLE +
+				dht11->num_edges - DHT11_EDGES_PER_READ;
+		for (; offset >= 0; --offset) {
+			ret = dht11_decode(dht11, offset);
+			if (!ret)
+				break;
+		}
+
+		if (ret)
+			goto err;
+	}
+
+	vals[0] = dht11->temperature;
+	vals[1] = dht11->humidity;
+	
+	/* put data into iio_buffer */
+	iio_push_to_buffers(iio_dev, vals);
+
+	if (dht11->temp_ev_enable)
+	{
+		if (vals[0] > dht11->temp_thres_up)
+		{
+			iio_push_event(iio_dev,
+					   IIO_UNMOD_EVENT_CODE(IIO_TEMP, 0,
+							IIO_EV_TYPE_THRESH, IIO_EV_DIR_RISING),
+					   iio_get_time_ns(iio_dev));
+		}
+
+		if (vals[0] < dht11->temp_thres_down)
+		{
+			iio_push_event(iio_dev,
+					   IIO_UNMOD_EVENT_CODE(IIO_TEMP, 0,
+							IIO_EV_TYPE_THRESH, IIO_EV_DIR_FALLING),
+					   iio_get_time_ns(iio_dev));
+		}
+    }
+		
+err:
+	dht11->num_edges = -1;
+	mutex_unlock(&dht11->lock);
+
+	iio_trigger_notify_done(iio_dev->trig);
+
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t dht11_event_handler(int irq, void *private)
+{
+	struct iio_poll_func *pf = private;
+	struct iio_dev *idev = pf->indio_dev;
+
+	iio_push_event(idev,
+			   IIO_UNMOD_EVENT_CODE(IIO_TEMP, 0,
+					IIO_EV_TYPE_THRESH, IIO_EV_DIR_RISING),
+			   iio_get_time_ns(idev));
+
+	iio_trigger_notify_done(idev->trig);
+
+	return IRQ_HANDLED;
+}
+
+static int dht11_buffer_init(struct iio_dev *indio_dev)
+{
+#if 0
+	struct iio_buffer *buffer;
+
+	buffer = iio_kfifo_allocate();
+	if (!buffer)
+		return -ENOMEM;
+
+	iio_device_attach_buffer(indio_dev, buffer);
+
+	/* Ring buffer functions - here trigger setup related */
+	indio_dev->setup_ops = &dht11_buf_setup_ops;
+
+	return 0;
+#else
+	//int ret = iio_triggered_event_setup(indio_dev, NULL, dht11_event_handler);
+	//if (ret)
+	//	return ret;
+	
+	return iio_triggered_buffer_setup(indio_dev, dht11_triggered_buf_handle, dht11_triggered_buf_thread, NULL);
+#endif	
+}
+
+static void dht11_work(struct work_struct *work)
+{
+	struct dht11 *dht11 = container_of(work, struct dht11, work.work);
+	int ret, timeres, offset;
+	struct iio_dev *iio_dev = dht11->iio;
+	uint8_t vals[2];
+	
+	/* read dht11 */
+	mutex_lock(&dht11->lock);
+	if (dht11->timestamp + DHT11_DATA_VALID_TIME < ktime_get_boottime_ns()) {
+		timeres = ktime_get_resolution_ns();
+		dev_dbg(dht11->dev, "current timeresolution: %dns\n", timeres);
+		if (timeres > DHT11_MIN_TIMERES) {
+			dev_err(dht11->dev, "timeresolution %dns too low\n",
+				timeres);
+			/* In theory a better clock could become available
+			 * at some point ... and there is no error code
+			 * that really fits better.
+			 */
+			ret = -EAGAIN;
+			goto err;
+		}
+		if (timeres > DHT11_AMBIG_LOW && timeres < DHT11_AMBIG_HIGH)
+			dev_warn(dht11->dev,
+				 "timeresolution: %dns - decoding ambiguous\n",
+				 timeres);
+
+		reinit_completion(&dht11->completion);
+
+		dht11->num_edges = 0;
+		ret = gpiod_direction_output(dht11->gpiod, 0);
+		if (ret)
+			goto err;
+		usleep_range(DHT11_START_TRANSMISSION_MIN,
+			     DHT11_START_TRANSMISSION_MAX);
+		ret = gpiod_direction_input(dht11->gpiod);
+		if (ret)
+			goto err;
+
+		ret = request_irq(dht11->irq, dht11_handle_irq,
+				  IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
+				  iio_dev->name, iio_dev);
+		if (ret)
+			goto err;
+
+		ret = wait_for_completion_killable_timeout(&dht11->completion,
+							   HZ);
+
+		free_irq(dht11->irq, iio_dev);
+
+#ifdef CONFIG_DYNAMIC_DEBUG
+		dht11_edges_print(dht11);
+#endif
+
+		if (ret == 0 && dht11->num_edges < DHT11_EDGES_PER_READ - 1) {
+			dev_err(dht11->dev, "Only %d signal edges detected\n",
+				dht11->num_edges);
+			ret = -ETIMEDOUT;
+		}
+		if (ret < 0)
+			goto err;
+
+		offset = DHT11_EDGES_PREAMBLE +
+				dht11->num_edges - DHT11_EDGES_PER_READ;
+		for (; offset >= 0; --offset) {
+			ret = dht11_decode(dht11, offset);
+			if (!ret)
+				break;
+		}
+
+		if (ret)
+			goto err;
+	}
+
+	vals[0] = dht11->temperature;
+	vals[1] = dht11->humidity;
+	
+	/* put data into iio_buffer */
+	iio_push_to_buffers(iio_dev, vals);
+	
+err:
+	dht11->num_edges = -1;
+	mutex_unlock(&dht11->lock);
+	
+	/* re-start work */
+	if (ret)
+	{
+		/* 有错误 */
+		schedule_delayed_work(&dht11->work, 0);
+	}
+	else
+	{
+		schedule_delayed_work(&dht11->work, HZ);
+	}
+}
+
+static const unsigned long dht11_scan_masks[] = {0x3, 0};
+
+static int dht11_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct dht11 *dht11;
+	struct iio_dev *iio;
+
+	iio = devm_iio_device_alloc(dev, sizeof(*dht11));
+	if (!iio) {
+		dev_err(dev, "Failed to allocate IIO device\n");
+		return -ENOMEM;
+	}
+
+	dht11 = iio_priv(iio);
+	dht11->dev = dev;
+	dht11->iio = iio;
+
+	dht11->gpiod = devm_gpiod_get(dev, NULL, GPIOD_IN);
+	if (IS_ERR(dht11->gpiod))
+		return PTR_ERR(dht11->gpiod);
+
+
+	dht11->irq = gpiod_to_irq(dht11->gpiod);
+	if (dht11->irq < 0) {
+		dev_err(dev, "GPIO %d has no interrupt\n", desc_to_gpio(dht11->gpiod));
+		return -EINVAL;
+	}
+
+	dht11->timestamp = ktime_get_boottime_ns() - DHT11_DATA_VALID_TIME - 1;
+	dht11->num_edges = -1;
+
+	platform_set_drvdata(pdev, iio);
+
+	init_completion(&dht11->completion);
+	mutex_init(&dht11->lock);
+	iio->name = pdev->name;
+	iio->dev.parent = &pdev->dev;
+	iio->info = &dht11_iio_info;
+	iio->modes = INDIO_DIRECT_MODE | INDIO_BUFFER_SOFTWARE;
+	iio->channels = dht11_chan_spec;
+	iio->num_channels = ARRAY_SIZE(dht11_chan_spec);
+	iio->available_scan_masks = dht11_scan_masks;
+
+	dht11_buffer_init(iio);
+
+	/* init work */
+	INIT_DELAYED_WORK(&dht11->work, dht11_work);
+
+	return devm_iio_device_register(dev, iio);
+}
+
+static struct platform_driver dht11_driver = {
+	.driver = {
+		.name	= DRIVER_NAME,
+		.of_match_table = dht11_dt_ids,
+	},
+	.probe  = dht11_probe,
+};
+
+module_platform_driver(dht11_driver);
+
+MODULE_AUTHOR("Harald Geyer <harald@ccbib.org>");
+MODULE_DESCRIPTION("DHT11 humidity/temperature sensor driver");
+MODULE_LICENSE("GPL v2");

STM32MP157/source/A7/14_iio/06_dht11_iio_event_课堂现场编写/dht11.dts

@@ -0,0 +1,4 @@
+humidity_sensor {
+	compatible = "dht11";
+    gpios = <&gpioa 5 GPIO_ACTIVE_HIGH>;
+};