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IMX6ULL/doc_pic/14_IIO/03_iio_trigger的使用.md

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+# iio_trigger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`
+
+
+
+## 1. iio_trigger的引入与体验
+
+### 1.1 问题引入
+
+在上一个驱动程序里，我们使用工作队列：读DHT11、写Buffer。
+
+工作队列的本质是：在一个内核线程(worker线程)里，执行我们提供的work函数。
+
+![image-20241120143037699](pic/image-20241120143037699.png)
+
+我们想使用更多的读数据方式，怎么办？比如：
+
+* 类似我们实现的使用内核线程不断读硬件、写buffer
+* 用户手工触发一次读硬件、写buffer
+* 使用其他中断，比如按键，按一下触发一次读硬件、写buffer
+* 定时触发一次读硬件、写buffer
+
+内核里已经实现了多种"iio-trigger"，比如：
+
+* iio-trig-loop：本质就是使用一个内核线程，不断读硬件、写buffer
+* iio-trig-sysfs：用户写一下某个sysfs文件，就读一次硬件、写buffer
+* iio-trig-interrupt：可以使用其他中断来读硬件、写buffer
+* iio-trig-hrtimer：使用定时器，周期性地读硬件、写buffer
+
+
+
+### 1.2 trigger的概念
+
+要使用trigger，首先得有驱动程序：配置内核，把如下驱动选上
+
+![image-20241120152309404](pic/image-20241120152309404.png)
+
+
+
+然后创建trigger：比如按照驱动程序iio-trig-loop.ko后，还需要执行如下命令来创建触发器：
+
+```shell
+mkdir  /sys/kernel/config/iio/triggers/loop/loop0
+```
+
+
+
+然后，要设置IIO设备使用触发器，比如：
+
+```shell
+insmod /root/dht11.ko
+cd /sys/bus/iio/devices/iio\:device2/
+echo loop0 > trigger/current_trigger                        # 在设备上使用trigger
+```
+
+
+
+最后：使能iio device的buffer、读设备
+
+
+
+### 1.3 上机体验
+
+IMX6ULL的源码：
+
+![image-20241120144844917](pic/image-20241120144844917.png)
+
+STM32MP157的源码：
+
+![image-20241120144923584](pic/image-20241120144923584.png)
+
+#### 1.3.1 IMX6ULL
+
+```shell
+insmod /root/iio-trig-loop.ko
+mkdir  /sys/kernel/config/iio/triggers/loop/loop0  # 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 loop0 > 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
+```
+
+
+
+#### 1.3.2 STM32MP157
+
+```SHELL
+insmod /root/iio-trig-loop.ko
+mkdir  /sys/kernel/config/iio/triggers/loop/loop0  # 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 loop0 > 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
+```
+
+
+
+
+
+## 2. iio_trigger内部机制
+
+以`drivers\iio\trigger\iio-trig-loop.c`为例进行分析：
+
+### 2.1 核心：虚拟中断控制器
+
+iio_trigger的核心是使用"虚拟中断控制器"来实现驱动的分离：
+
+![image-20241122105554105](pic/image-20241122105554105.png)
+
+以iio_trig-loop.c为例：
+
+* iio_trig-loop.c实现了一个虚拟中断控制器
+* DHT11提供虚拟的中断处理函数
+* 当使能DHT11的buffer时，向虚拟中断控制器注册中断
+* iio_trig-loop.c的线程调用`iio_trigger_poll_chained`函数直接调用中断处理函数
+* **注意**：没有真正的中断产生
+
+![image-20241122102016616](pic/image-20241122102016616.png)
+
+### 2.2 注册iio_trigger驱动
+
+执行如下命令：
+
+```shell
+insmod /root/iio-trig-loop.ko
+```
+
+会生成一个目录（以后在此目录下mkdir，就会创建trigger设备，即创建虚拟中断控制器）：
+
+```shell
+/sys/kernel/config/iio/triggers/loop
+```
+
+![image-20241120162213861](pic/image-20241120162213861.png)
+
+### 2.3 创建trigger设备：创建虚拟中断控制器
+
+执行如下命令：
+
+```shell
+mkdir  /sys/kernel/config/iio/triggers/loop/loop0  # 创建trigger
+cat /sys/bus/iio/devices/trigger1/name             # 可以看到这个trigger
+```
+
+就会创建trigger设备，就是创建虚拟中断控制器：
+
+![image-20241122102856636](pic/image-20241122102856636.png)
+
+
+
+### 2.4 iio_device使用trigger设备
+
+iio_device要使用trigger功能，就是去注册一个中断，这个中断是trigger设备提供的虚拟的中断。
+
+#### 2.4.1 准备中断函数
+
+创建buffer时提供handler、thread_fn：
+
+![image-20241122103612419](pic/image-20241122103612419.png)
+
+#### 2.4.2 注册中断函数
+
+使能buffer时注册中断函数，执行如下命令时：
+
+```shell
+echo 1 > scan_elements/in_humidityrelative_en
+echo 1 > scan_elements/in_temp_en
+echo 1 > buffer/enable
+```
+
+会有如下调用：
+
+![image-20241122104728332](pic/image-20241122104728332.png)
+
+### 2.5 trigger设备调用中断处理函数
+
+使能buffer时，会设置trigger的状态为true：
+
+![image-20241122174847707](pic/image-20241122174847707.png)
+
+对于iio-trig-loop.c:
+
+![image-20241122175029650](pic/image-20241122175029650.png)
+
+
+
+iio_trigger_poll_chained会直接调用iio_device提供的中断处理函数：
+
+![image-20241122175306406](pic/image-20241122175306406.png)
+
+
+
+
+
+## 3. iio-trig-hrtimer分析
+
+### 3.1 注册trigger驱动
+
+```shell
+insmod iio-trig-hrtimer.ko
+ls /sys/kernel/config/iio/triggers/hrtimer/
+```
+
+
+
+
+
+### 3.2 创建trigger设备
+
+```shell
+cd /sys/kernel/config/iio/triggers/hrtimer/
+mkdir timer_abc
+
+# ls /sys/bus/iio/devices/trigger1/
+name                power/              sampling_frequency  subsystem/          uevent
+# cat /sys/bus/iio/devices/trigger1/name
+timer_abc
+
+```
+
+
+
+
+
+### 3.3 使用
+
+#### 3.3.1 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
+
+# 修改频率
+cd /sys/bus/iio/devices/trigger1
+echo 1000000000 > sampling_frequency  # 单位ns
+```
+
+
+
+#### 3.3.2 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
+
+# 修改频率
+cd /sys/bus/iio/devices/trigger1
+echo 1000000000 > sampling_frequency  # 单位ns
+```
+
+
+
+
+
+## 4. 修改DHT11驱动使用iio_trigger
+
+IMX6ULL的源码：
+
+![image-20241125103916918](pic/image-20241125103916918.png)
+
+
+
+STM32MP157的源码：
+
+![image-20241125103834678](pic/image-20241125103834678.png)
+
+### 4.1 设置triggered_buffer
+
+核心有2点：
+
+* 设置pollfunc结构体，里面记录有虚拟中断处理函数：handle、thread_fn
+* 提供setup_ops，它里面有postenable函数指针，用来在使能buffer时注册虚拟的中断
+
+IIO子系统里提供了现成的函数：
+
+![image-20241125105034175](pic/image-20241125105034175.png)
+
+
+
+### 4.2 实现中断处理函数
+
+先实现handle函数：
+
+![image-20241125105104461](pic/image-20241125105104461.png)
+
+
+
+再实现thread_fn函数：
+
+![image-20241125105301615](pic/image-20241125105301615.png)
+
+
+
+### 4.3 上机实验
+
+#### 4.3.1 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
+
+# 修改频率
+cd /sys/bus/iio/devices/trigger1
+echo 1000000000 > sampling_frequency  # 单位ns
+```
+
+
+
+#### 4.3.2 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
+
+# 修改频率
+cd /sys/bus/iio/devices/trigger1
+echo 1000000000 > sampling_frequency  # 单位ns
+```
+
+
+
+### 4.4 代码调用流程回顾
+
+
+

IMX6ULL/source/14_iio/03_dht11_iio_trigger/dht11.c

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+/*
+ * 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>
+
+#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_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,
+		},
+	},
+	{ .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,
+};
+
+irqreturn_t dht11_irq_handler(int irq, void *p)
+{
+	return IRQ_WAKE_THREAD;
+}
+
+/**
+ * Transfer data from hardware to KFIFO.
+ */
+irqreturn_t dht11_read_datas(int irq, void *p)
+{
+	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);
+	
+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_irq_handler,
+						dht11_read_datas,
+						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 | INDIO_BUFFER_TRIGGERED;
+	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/03_dht11_iio_trigger/dht11.dts

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

IMX6ULL/source/14_iio/04_dht11_iio_trigger_课堂现场编写/dht11.c

@@ -0,0 +1,637 @@
+/*
+ * 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>
+
+#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_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,
+		},
+	},
+	{ .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);
+	
+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/04_dht11_iio_trigger_课堂现场编写/dht11.dts

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

README.md

@@ -914,6 +914,15 @@ git clone https://e.coding.net/weidongshan/linux/doc_and_source_for_drivers.git
   02.3_实现iio_buffer的写入
   ```
 
+* 2024.11.25  发布IIO"子系统"
+
+  ```shell
+  03.1_iio_trigger的引入与体验
+  03.2_iio_trigger内部机制
+  03.3_iio-trig-hrtimer分析
+  03.4_修改DHT11驱动使用iio_trigger
+  ```
+
   
 
 ## 6. 联系方式

STM32MP157/doc_pic/14_IIO/03_iio_trigger的使用.md

@@ -0,0 +1,389 @@
+# iio_trigger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`
+
+
+
+## 1. iio_trigger的引入与体验
+
+### 1.1 问题引入
+
+在上一个驱动程序里，我们使用工作队列：读DHT11、写Buffer。
+
+工作队列的本质是：在一个内核线程(worker线程)里，执行我们提供的work函数。
+
+![image-20241120143037699](pic/image-20241120143037699.png)
+
+我们想使用更多的读数据方式，怎么办？比如：
+
+* 类似我们实现的使用内核线程不断读硬件、写buffer
+* 用户手工触发一次读硬件、写buffer
+* 使用其他中断，比如按键，按一下触发一次读硬件、写buffer
+* 定时触发一次读硬件、写buffer
+
+内核里已经实现了多种"iio-trigger"，比如：
+
+* iio-trig-loop：本质就是使用一个内核线程，不断读硬件、写buffer
+* iio-trig-sysfs：用户写一下某个sysfs文件，就读一次硬件、写buffer
+* iio-trig-interrupt：可以使用其他中断来读硬件、写buffer
+* iio-trig-hrtimer：使用定时器，周期性地读硬件、写buffer
+
+
+
+### 1.2 trigger的概念
+
+要使用trigger，首先得有驱动程序：配置内核，把如下驱动选上
+
+![image-20241120152309404](pic/image-20241120152309404.png)
+
+
+
+然后创建trigger：比如按照驱动程序iio-trig-loop.ko后，还需要执行如下命令来创建触发器：
+
+```shell
+mkdir  /sys/kernel/config/iio/triggers/loop/loop0
+```
+
+
+
+然后，要设置IIO设备使用触发器，比如：
+
+```shell
+insmod /root/dht11.ko
+cd /sys/bus/iio/devices/iio\:device2/
+echo loop0 > trigger/current_trigger                        # 在设备上使用trigger
+```
+
+
+
+最后：使能iio device的buffer、读设备
+
+
+
+### 1.3 上机体验
+
+IMX6ULL的源码：
+
+![image-20241120144844917](pic/image-20241120144844917.png)
+
+STM32MP157的源码：
+
+![image-20241120144923584](pic/image-20241120144923584.png)
+
+#### 1.3.1 IMX6ULL
+
+```shell
+insmod /root/iio-trig-loop.ko
+mkdir  /sys/kernel/config/iio/triggers/loop/loop0  # 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 loop0 > 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
+```
+
+
+
+#### 1.3.2 STM32MP157
+
+```SHELL
+insmod /root/iio-trig-loop.ko
+mkdir  /sys/kernel/config/iio/triggers/loop/loop0  # 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 loop0 > 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
+```
+
+
+
+
+
+## 2. iio_trigger内部机制
+
+以`drivers\iio\trigger\iio-trig-loop.c`为例进行分析：
+
+### 2.1 核心：虚拟中断控制器
+
+iio_trigger的核心是使用"虚拟中断控制器"来实现驱动的分离：
+
+![image-20241122105554105](pic/image-20241122105554105.png)
+
+以iio_trig-loop.c为例：
+
+* iio_trig-loop.c实现了一个虚拟中断控制器
+* DHT11提供虚拟的中断处理函数
+* 当使能DHT11的buffer时，向虚拟中断控制器注册中断
+* iio_trig-loop.c的线程调用`iio_trigger_poll_chained`函数直接调用中断处理函数
+* **注意**：没有真正的中断产生
+
+![image-20241122102016616](pic/image-20241122102016616.png)
+
+### 2.2 注册iio_trigger驱动
+
+执行如下命令：
+
+```shell
+insmod /root/iio-trig-loop.ko
+```
+
+会生成一个目录（以后在此目录下mkdir，就会创建trigger设备，即创建虚拟中断控制器）：
+
+```shell
+/sys/kernel/config/iio/triggers/loop
+```
+
+![image-20241120162213861](pic/image-20241120162213861.png)
+
+### 2.3 创建trigger设备：创建虚拟中断控制器
+
+执行如下命令：
+
+```shell
+mkdir  /sys/kernel/config/iio/triggers/loop/loop0  # 创建trigger
+cat /sys/bus/iio/devices/trigger1/name             # 可以看到这个trigger
+```
+
+就会创建trigger设备，就是创建虚拟中断控制器：
+
+![image-20241122102856636](pic/image-20241122102856636.png)
+
+
+
+### 2.4 iio_device使用trigger设备
+
+iio_device要使用trigger功能，就是去注册一个中断，这个中断是trigger设备提供的虚拟的中断。
+
+#### 2.4.1 准备中断函数
+
+创建buffer时提供handler、thread_fn：
+
+![image-20241122103612419](pic/image-20241122103612419.png)
+
+#### 2.4.2 注册中断函数
+
+使能buffer时注册中断函数，执行如下命令时：
+
+```shell
+echo 1 > scan_elements/in_humidityrelative_en
+echo 1 > scan_elements/in_temp_en
+echo 1 > buffer/enable
+```
+
+会有如下调用：
+
+![image-20241122104728332](pic/image-20241122104728332.png)
+
+### 2.5 trigger设备调用中断处理函数
+
+使能buffer时，会设置trigger的状态为true：
+
+![image-20241122174847707](pic/image-20241122174847707.png)
+
+对于iio-trig-loop.c:
+
+![image-20241122175029650](pic/image-20241122175029650.png)
+
+
+
+iio_trigger_poll_chained会直接调用iio_device提供的中断处理函数：
+
+![image-20241122175306406](pic/image-20241122175306406.png)
+
+
+
+
+
+## 3. iio-trig-hrtimer分析
+
+### 3.1 注册trigger驱动
+
+```shell
+insmod iio-trig-hrtimer.ko
+ls /sys/kernel/config/iio/triggers/hrtimer/
+```
+
+
+
+
+
+### 3.2 创建trigger设备
+
+```shell
+cd /sys/kernel/config/iio/triggers/hrtimer/
+mkdir timer_abc
+
+# ls /sys/bus/iio/devices/trigger1/
+name                power/              sampling_frequency  subsystem/          uevent
+# cat /sys/bus/iio/devices/trigger1/name
+timer_abc
+
+```
+
+
+
+
+
+### 3.3 使用
+
+#### 3.3.1 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
+
+# 修改频率
+cd /sys/bus/iio/devices/trigger1
+echo 1000000000 > sampling_frequency  # 单位ns
+```
+
+
+
+#### 3.3.2 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
+
+# 修改频率
+cd /sys/bus/iio/devices/trigger1
+echo 1000000000 > sampling_frequency  # 单位ns
+```
+
+
+
+
+
+## 4. 修改DHT11驱动使用iio_trigger
+
+IMX6ULL的源码：
+
+![image-20241125103916918](pic/image-20241125103916918.png)
+
+
+
+STM32MP157的源码：
+
+![image-20241125103834678](pic/image-20241125103834678.png)
+
+### 4.1 设置triggered_buffer
+
+核心有2点：
+
+* 设置pollfunc结构体，里面记录有虚拟中断处理函数：handle、thread_fn
+* 提供setup_ops，它里面有postenable函数指针，用来在使能buffer时注册虚拟的中断
+
+IIO子系统里提供了现成的函数：
+
+![image-20241125105034175](pic/image-20241125105034175.png)
+
+
+
+### 4.2 实现中断处理函数
+
+先实现handle函数：
+
+![image-20241125105104461](pic/image-20241125105104461.png)
+
+
+
+再实现thread_fn函数：
+
+![image-20241125105301615](pic/image-20241125105301615.png)
+
+
+
+### 4.3 上机实验
+
+#### 4.3.1 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
+
+# 修改频率
+cd /sys/bus/iio/devices/trigger1
+echo 1000000000 > sampling_frequency  # 单位ns
+```
+
+
+
+#### 4.3.2 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
+
+# 修改频率
+cd /sys/bus/iio/devices/trigger1
+echo 1000000000 > sampling_frequency  # 单位ns
+```
+
+
+
+### 4.4 代码调用流程回顾
+
+
+

STM32MP157/source/A7/14_iio/03_dht11_iio_trigger/dht11.c

@@ -0,0 +1,617 @@
+/*
+ * 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>
+
+#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_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,
+		},
+	},
+	{ .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);
+	
+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_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/03_dht11_iio_trigger/dht11.dts

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

STM32MP157/source/A7/14_iio/04_dht11_iio_trigger_课堂现场编写/dht11.c

@@ -0,0 +1,617 @@
+/*
+ * 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>
+
+#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_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,
+		},
+	},
+	{ .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);
+	
+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_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/04_dht11_iio_trigger_课堂现场编写/dht11.dts

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