驱动实例2

Linux USB gadget设备驱动解析（4）--编写一个gadget驱动作者：刘洪涛，华清远见嵌入式学院讲师。

一、编写计划通过前面几节的基础，本节计划编写一个简单的gadget驱动。

重在让大家快速了解gadget驱动结构。

上节中简单介绍了zero.c程序。

这个程序考虑到了多配置、高速传输、USB OTG等因素。

应该说写的比较清楚，是我们了解gadget驱动架构的一个非常好的途径。

但把这些东西都放在一起，对很多初学人员来说还是不能快速理解。

那就再把它简化一些，针对S3C2410平台，只实现一个配置、一个接口、一个端点，不考虑高速及OTG的情况。

只完成单向从host端接收数据的功能，但要把字符设备驱动结合在里面。

这需要有一个host端的驱动，来完成向device端发送数据。

关于在主机端编写一个简单的USB设备驱动程序，有很多的资料。

相信大家很快就会完成的。

二、功能展示1、PC端编写了一个usbtransfer.ko，能够向device端发送数据2、对目标平台编写一个gadget驱动，名称是g_zero.ko3、测试步骤在目标平台（基于S3C2410）上加载gadget驱动# insmod g_zero.koname=ep1-bulksmdk2410_udc: Pull-up enable# mknod /dev/usb_rcv c 251 0#在PC主机上加载驱动usbtransfer.ko#insmod usbtransfer.ko#mknod /dev/usbtransfer c 266 0连接设备，目标平台的终端显示：connected目标平台读取数据# cat /dev/usb_rcvPC端发送数据#echo “12345” > /dev/usbtransfer#echo “abcd” > /dev/usbtransfer设备端会显示收到的数据# cat /dev/usb_rcv12345abcd三、代码分析下面的代码是在原有的zero.c基础上做了精简、修改的。

一些结构的名称还是保留以前的，但含义有所变化。

如：loopback_config，不再表示loopback，而只是单向的接收数据。

/** zero.c -- Gadget Zero, for simple USB development* lht@* All rights reserved.*//* #define VERBOSE_DEBUG */#include <linux/kernel.h>#include <linux/utsname.h>#include <linux/device.h>#include <linux/usb/ch9.h>#include <linux/usb/gadget.h>#include "gadget_chips.h"#include <linux/slab.h>#include <linux/module.h>#include <linux/init.h>#include <linux/usb/input.h>#include <linux/cdev.h>#include <asm/uaccess.h>#include <linux/fs.h>#include <linux/poll.h>#include <linux/types.h> /* size_t */#include <linux/errno.h> /* error codes */#include <asm/system.h>#include <asm/io.h>#include <linux/sched.h>/*-------------------------------------------------------------------------*/ static const char shortname[] = "zero";static const char loopback[] = "loop input to output";static const char longname[] = "Gadget Zero";static const char source_sink[] = "source and sink data";#define STRING_MANUFACTURER 25#define STRING_PRODUCT 42#define STRING_SERIAL 101#define STRING_SOURCE_SINK 250#define STRING_LOOPBACK 251//#define DRIVER_VENDOR_NUM 0x0525 /* NetChip *///#define DRIVER_PRODUCT_NUM 0xa4a0 /* Linux-USB "Gadget Zero" */ #define DRIVER_VENDOR_NUM 0x5345 /* NetChip */#define DRIVER_PRODUCT_NUM 0x1234 /* Linux-USB "Gadget Zero" */ static int usb_zero_major = 251;/*-------------------------------------------------------------------------*/static const char *EP_OUT_NAME; /* sink *//*-------------------------------------------------------------------------*//* big enough to hold our biggest descriptor */#define USB_BUFSIZ 256struct zero_dev { //zero设备结构spinlock_t lock;struct usb_gadget *gadget;struct usb_request *req; /* for control responses */struct usb_ep *out_ep;struct cdev cdev;unsigned char data[128];unsigned int data_size;wait_queue_head_t bulkrq;};#define CONFIG_LOOPBACK 2static struct usb_device_descriptor device_desc = { //设备描述符.bLength = sizeof device_desc,.bDescriptorType = USB_DT_DEVICE,.bcdUSB = __constant_cpu_to_le16(0x0110),.bDeviceClass = USB_CLASS_VENDOR_SPEC,.idVendor = __constant_cpu_to_le16(DRIVER_VENDOR_NUM),.idProduct = __constant_cpu_to_le16(DRIVER_PRODUCT_NUM),.iManufacturer = STRING_MANUFACTURER,.iProduct = STRING_PRODUCT,.iSerialNumber = STRING_SERIAL,.bNumConfigurations = 1,};static struct usb_endpoint_descriptor fs_sink_desc = { //端点描述符.bLength = USB_DT_ENDPOINT_SIZE,.bDescriptorType = USB_DT_ENDPOINT,.bEndpointAddress = USB_DIR_OUT, //对主机端来说，输出.bmAttributes = USB_ENDPOINT_XFER_BULK,};static struct usb_config_descriptor loopback_config = { //配置描述符.bLength = sizeof loopback_config,.bDescriptorType = USB_DT_CONFIG,/* compute wTotalLength on the fly */.bNumInterfaces = 1,.bConfigurationValue = CONFIG_LOOPBACK,.iConfiguration = STRING_LOOPBACK,.bmAttributes = USB_CONFIG_ATT_ONE | USB_CONFIG_ATT_SELFPOWER, .bMaxPower = 1, /* self-powered */};static const struct usb_interface_descriptor loopback_intf = { //接口描述符.bLength = sizeof loopback_intf,.bDescriptorType = USB_DT_INTERFACE,.bNumEndpoints = 1,.bInterfaceClass = USB_CLASS_VENDOR_SPEC,.iInterface = STRING_LOOPBACK,};/* static strings, in UTF-8 */#define STRING_MANUFACTURER 25#define STRING_PRODUCT 42#define STRING_SERIAL 101#define STRING_SOURCE_SINK 250#define STRING_LOOPBACK 251static char manufacturer[50];/* default serial number takes at least two packets */static char serial[] = "0123456789.0123456789.0123456789"; static struct usb_string strings[] = { //字符串描述符{ STRING_MANUFACTURER, manufacturer, },{ STRING_PRODUCT, longname, },{ STRING_SERIAL, serial, },{ STRING_LOOPBACK, loopback, },{ STRING_SOURCE_SINK, source_sink, },{ } /* end of list */};static struct usb_gadget_strings stringtab = {.language = 0x0409, /* en-us */.strings = strings,};static const struct usb_descriptor_header *fs_loopback_function[] = { (struct usb_descriptor_header *) &loopback_intf,(struct usb_descriptor_header *) &fs_sink_desc,NULL,};static intusb_zero_open (struct inode *inode, struct file *file) //打开设备{struct zero_dev *dev =container_of (inode->i_cdev, struct zero_dev, cdev);file->private_data = dev;init_waitqueue_head (&dev->bulkrq);return 0;}static intusb_zero_release (struct inode *inode, struct file *file) //关闭设备{return 0;}static void free_ep_req(struct usb_ep *ep, struct usb_request *req){kfree(req->buf);usb_ep_free_request(ep, req);}static struct usb_request *alloc_ep_req(struct usb_ep *ep, unsigned length)//分配请求 {struct usb_request *req;req = usb_ep_alloc_request(ep, GFP_ATOMIC);if (req) {req->length = length;req->buf = kmalloc(length, GFP_ATOMIC);if (!req->buf) {usb_ep_free_request(ep, req);req = NULL;}}return req;}static void source_sink_complete(struct usb_ep *ep, struct usb_request *req)//请求完成函数 {struct zero_dev *dev = ep->driver_data;int status = req->status;switch (status) {case 0: /* normal completion */if (ep == dev->out_ep) {memcpy(dev->data, req->buf, req-> actual);//返回数据拷贝到req->buf 中， //dev->data_size=req->length; dev->data_size=req->actual; //实际长度为req-> actual；需要确认req –>short_not_ok为0。