Android4.0 USB挂载内核驱动层流程分析（一）

http://blog.csdn.net/airk000/article/details/7887645

1.platform_device
在arch/arm/mach-msm/Board-xx.c中：

 static struct platform_device android_usb_device = {
 .name = "android_usb",
 .id = -1,
 .dev = {
 .platform_data = &android_usb_pdata,  //@1
 }

 };
 static struct android_usb_platform_data android_usb_pdata = {
 .update_pid_and_serial_num = usb_diag_update_pid_and_serial_num,
 };

在rpc_hsusb.c中：

 int usb_diag_update_pid_and_serial_num(uint32_t pid, const char *snum)
 {
 int ret;

 ret = msm_hsusb_send_productID(pid);
 if (ret)
 return ret;

 if (!snum) {
 ret = msm_hsusb_is_serial_num_null(1);
 if (ret)
 return ret;
 return 0;
 }

 ret = msm_hsusb_is_serial_num_null(0);
 if (ret)
 return ret;
 ret = msm_hsusb_send_serial_number(snum);
 if (ret)
 return ret;

 return 0;
 }

在内核初始化时，先注册了名为android_usb的设备。

2.platform_driver

在drivers/usb/gadget/Android.c中：

 static struct platform_driver android_platform_driver = {
 .driver = { .name = "android_usb"},
 };

注册了名为android_usb的paltform_driver。但是并不像其他硬件驱动那样，有.probe函数用来匹配驱动。不要着急，慢慢看。

3.module_init

其实Android.c用的是module_init的方式：

 static int __init init(void)
 {
 struct android_dev *dev;
 int err;

 android_class = class_create(THIS_MODULE, "android_usb");    //在sys/class下创建android_usb目录
 if (IS_ERR(android_class))    //错误处理
 return PTR_ERR(android_class);

 dev = kzalloc(sizeof(*dev), GFP_KERNEL);
 if (!dev)
 return -ENOMEM;

 dev->functions = supported_functions;    //设备支持的一些功能，功能列表
 /*
 *static struct android_usb_function *supported_functions[] = {
 * &rmnet_smd_function,
 * &rmnet_sdio_function,
 * &rmnet_smd_sdio_function,
 * &rmnet_function,
 * &diag_function,
 * &serial_function,
 * &adb_function,
 * &ccid_function,
 *// &acm_function,
 * &mtp_function,
 * &ptp_function,
 * &rndis_function,
 * &mass_storage_function,
 * &accessory_function,
 * NULL
 *};
 */
 INIT_LIST_HEAD(&dev->enabled_functions);    //应该是加入到队列里的意思吧，使能这些功能
 INIT_WORK(&dev->work, android_work);

 err = android_create_device(dev);    //创建dev，按内核目录来看：
 /*
 *localhost android_usb # ls
 *android0          f_diag            f_rmnet           f_rndis
 *f_accessory       f_mass_storage    f_rmnet_sdio      f_serial
 *f_adb             f_mtp             f_rmnet_smd
 *f_ccid            f_ptp             f_rmnet_smd_sdio
 *localhost android_usb #
 */
 if (err) {
 class_destroy(android_class);
 kfree(dev);
 return err;
 }

 _android_dev = dev;

 /* Override composite driver functions */
 composite_driver.setup = android_setup;
 composite_driver.disconnect = android_disconnect;

 platform_driver_probe(&android_platform_driver, android_probe);    //驱动是通过platform_driver_probe方式进行匹配的，匹配函数位android_probe:
 /*
 *static int __devinit android_probe(struct platform_device *pdev)
 *{
 * struct android_usb_platform_data *pdata = pdev->dev.platform_data;    //见@1
 * struct android_dev *dev = _android_dev;
 *
 * dev->pdata = pdata;
 *
 * return 0;
 *}
 */

 return usb_composite_probe(&android_usb_driver, android_bind);    //万能USB驱动，用android_bind进行绑定
 }
 module_init(init);

 static void __exit cleanup(void)
 {
 usb_composite_unregister(&android_usb_driver);
 class_destroy(android_class);
 kfree(_android_dev);
 _android_dev = NULL;
 }
 module_exit(cleanup);

我认为是有两个重点，一个是supported_functions，另一个是android_bind。下一篇博客继续分析。