add 09_UART/13

STM32MP157/doc_pic/09_UART/13_编写虚拟UART驱动程序_框架.md

@@ -0,0 +1,77 @@
+## 编写虚拟UART驱动程序_框架
+
+* 参考代码
+
+  ```shell
+  硬件相关：
+  drivers/tty/serial/imx.c
+  drivers/tty/serial/stm32-usart.c
+  
+  串口核心层：
+  drivers/tty/serial/serial_core.c
+  
+  TTY层:
+  drivers/tty/tty_io.c
+  ```
+
+  
+
+* 本节课程源码在GIT仓库里
+
+  ```shell
+  doc_and_source_for_drivers\IMX6ULL\source\09_UART
+  	04_virtual_uart_driver
+  doc_and_source_for_drivers\STM32MP157\source\A7\09_UART
+  	04_virtual_uart_driver
+  ```
+  
+  
+
+### 1. 框架回顾
+
+![image-20210724153515059](pic/09_UART/24_tty_driver_level_2.png)
+
+
+
+### 2. 编写UART驱动要做的事
+
+![image-20210730142813809](pic/09_UART/39_uart_driver.png)
+
+
+
+* 注册一个uart_driver：它里面有名字、主次设备号等
+* 对于每一个port，调用uart_add_one_port，里面的核心是uart_ops，提供了硬件操作函数
+  * uart_add_one_port由platform_driver的probe函数调用
+  * 所以：
+    * 编写设备树节点
+    * 注册platform_driver
+
+
+
+### 3. 虚拟的UART
+
+![image-20210730150445225](pic/09_UART/40_virtual_uart.png)
+
+为了做实验，我们还要创建一个虚拟文件：/proc/virt_uart_buf
+
+* 要发数据给虚拟串口时，执行：echo "xxx" > /proc/virt_uart_buf
+* 要读取虚拟串口的数据时，执行：cat /proc/virt_uart_buf
+
+
+
+
+
+### 4. 编程
+
+#### 4.1 编写设备树
+
+#### 4.2 编写uart_driver
+
+#### 4.3 编写platform_driver
+
+#### 4.4 实现uart_ops
+
+#### 4.5 实现/proc/virt_uart_buf
+
+
+

STM32MP157/source/A7/09_UART/04_virtual_uart_driver/virtual_uart.c

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+#include <linux/module.h>
+#include <linux/ioport.h>
+#include <linux/init.h>
+#include <linux/console.h>
+#include <linux/sysrq.h>
+#include <linux/platform_device.h>
+#include <linux/tty.h>
+#include <linux/tty_flip.h>
+#include <linux/serial_core.h>
+#include <linux/serial.h>
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/rational.h>
+#include <linux/reset.h>
+#include <linux/slab.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/io.h>
+#include <linux/dma-mapping.h>
+
+#include <asm/irq.h>
+
+static struct uart_driver virt_uart_drv = {
+	.owner          = THIS_MODULE,
+	.driver_name    = "VIRT_UART",
+	.dev_name       = "ttyVIRT",
+	.major          = 0,
+	.minor          = 0,
+	.nr             = 1,
+};
+
+
+static int virtual_uart_probe(struct platform_device *pdev)
+{	
+	uart_add_one_port(struct uart_driver * drv, struct uart_port * uport);
+	
+	return 0;
+}
+static int virtual_uart_remove(struct platform_device *pdev)
+{
+	
+	return 0;
+}
+
+
+
+static const struct of_device_id virtual_uart_of_match[] = {
+	{ .compatible = "100ask,virtual_uart", },
+	{ },
+};
+
+
+static struct platform_driver virtual_uart_driver = {
+	.probe		= virtual_uart_probe,
+	.remove		= virtual_uart_remove,
+	.driver		= {
+		.name	= "100ask_virtual_uart",
+		.of_match_table = of_match_ptr(virtual_uart_of_match),
+	}
+};
+
+
+/* 1. 入口函数 */
+static int __init virtual_uart_init(void)
+{	
+	printk("%s %s %d\n", __FILE__, __FUNCTION__, __LINE__);
+	
+	int ret = uart_register_driver(&virt_uart_drv);
+
+	if (ret)
+		return ret;
+	
+	/* 1.1 注册一个platform_driver */
+	return platform_driver_register(&virtual_uart_driver);
+}
+
+
+/* 2. 出口函数 */
+static void __exit virtual_uart_exit(void)
+{
+	printk("%s %s %d\n", __FILE__, __FUNCTION__, __LINE__);
+	/* 2.1 反注册platform_driver */
+	platform_driver_unregister(&virtual_uart_driver);
+}
+
+module_init(virtual_uart_init);
+module_exit(virtual_uart_exit);
+
+MODULE_LICENSE("GPL");
+
+

STM32MP157/source/A7/09_UART/04_virtual_uart_driver/virtual_uart.dts

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+
+
+/{
+	virtual_uart: virtual_uart_100ask {
+		compatible = "100ask,virtual_uart";
+		
+		interrupt-parent = <&intc>;
+		interrupts = <GIC_SPI 99 IRQ_TYPE_LEVEL_HIGH>;
+		
+	};
+	
+	
+};