arm 驱动进阶：usb驱动程序设计过程与实现

usb驱动程序设计实现步骤：

 

usb总线驱动内核代码分析过程：

hub_irq
    kick_khubd
        hub_thread
            hub_events
                hub_port_connect_change
                
                        udev = usb_alloc_dev(hdev, hdev->bus, port1);
                                dev->dev.bus = &usb_bus_type;
                
                        choose_address(udev); // 给新设备分配编号(地址)
                    
                    
                        hub_port_init   // usb 1-1: new full speed USB device using s3c2410-ohci and address 3
                        
                            hub_set_address  // 把编号(地址)告诉USB设备
                        
                            usb_get_device_descriptor(udev, 8); // 获取设备描述符
                            retval = usb_get_device_descriptor(udev, USB_DT_DEVICE_SIZE);
                        
                        usb_new_device(udev)   
                            err = usb_get_configuration(udev); // 把所有的描述符都读出来，并解析
                            usb_parse_configuration
                            
                            device_add  // 把device放入usb_bus_type的dev链表, 
                                        // 从usb_bus_type的driver链表里取出usb_driver，
                                        // 把usb_interface和usb_driver的id_table比较
                                        // 如果能匹配，调用usb_driver的probe

 

usb驱动程序代码实现：

/*
 * drivers\hid\usbhid\usbmouse.c
 */

#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/usb/input.h>
#include <linux/hid.h>

static struct input_dev *uk_dev;
static char *usb_buf;
static dma_addr_t usb_buf_phys;
static int len;
static struct urb *uk_urb;

static struct usb_device_id usbmouse_as_key_id_table [] = {
    { USB_INTERFACE_INFO(USB_INTERFACE_CLASS_HID, USB_INTERFACE_SUBCLASS_BOOT,
        USB_INTERFACE_PROTOCOL_MOUSE) },
    //{USB_DEVICE(0x1234,0x5678)},
    { }    /* Terminating entry */
};

static void usbmouse_as_key_irq(struct urb *urb)
{
    static unsigned char pre_val;
#if 0    
    int i;
    static int cnt = 0;
    printk("data cnt %d: ", ++cnt);
    for (i = 0; i < len; i++)
    {
        printk("%02x ", usb_buf[i]);
    }
    printk("\n");
#endif
    /* USB鼠标数据含义
     * data[0]: bit0-左键, 1-按下, 0-松开
     *          bit1-右键, 1-按下, 0-松开
     *          bit2-中键, 1-按下, 0-松开 
     *
     */
    if ((pre_val & (1<<0)) != (usb_buf[0] & (1<<0)))
    {
        /* 左键发生了变化 */
        input_event(uk_dev, EV_KEY, KEY_L, (usb_buf[0] & (1<<0)) ? 1 : 0);
        input_sync(uk_dev);
    }

    if ((pre_val & (1<<1)) != (usb_buf[0] & (1<<1)))
    {
        /* 右键发生了变化 */
        input_event(uk_dev, EV_KEY, KEY_S, (usb_buf[0] & (1<<1)) ? 1 : 0);
        input_sync(uk_dev);
    }

    if ((pre_val & (1<<2)) != (usb_buf[0] & (1<<2)))
    {
        /* 中键发生了变化 */
        input_event(uk_dev, EV_KEY, KEY_ENTER, (usb_buf[0] & (1<<2)) ? 1 : 0);
        input_sync(uk_dev);
    }
    
    pre_val = usb_buf[0];

    /* 重新提交urb */
    usb_submit_urb(uk_urb, GFP_KERNEL);
}

static int usbmouse_as_key_probe(struct usb_interface *intf, const struct usb_device_id *id)
{
    struct usb_device *dev;
    struct usb_host_interface *interface;
    struct usb_endpoint_descriptor *endpoint;
    int pipe;
    
    dev                = interface_to_usbdev(intf);
    interface     = intf->cur_altsetting;
    endpoint     = &interface->endpoint[0].desc;

    /* a. 分配一个input_dev */
    uk_dev = input_allocate_device();
    
    /* b. 设置 */
    /* b.1 能产生哪类事件 */
    set_bit(EV_KEY, uk_dev->evbit);
    set_bit(EV_REP, uk_dev->evbit);
    
    /* b.2 能产生哪些事件 */
    set_bit(KEY_L, uk_dev->keybit);
    set_bit(KEY_S, uk_dev->keybit);
    set_bit(KEY_ENTER, uk_dev->keybit);
    
    /* c. 注册 */
    input_register_device(uk_dev);
    
    /* d. 硬件相关操作 */
    /* 数据传输3要素: 源,目的,长度 */
    /* 源: USB设备的某个端点 */
    pipe = usb_rcvintpipe(dev, endpoint->bEndpointAddress);

    /* 长度: */
    len = endpoint->wMaxPacketSize;

    /* 目的: */
    usb_buf = usb_buffer_alloc(dev, len, GFP_ATOMIC, &usb_buf_phys);    // GFP_KERNEL, 是一个内存申请的 flag, 通常内存申请都用这个 flag, 除非是中断上下文 , 不能睡眠 , 那就得用 GPF_ATOMIC

    /* 使用"3要素" */
    /* 分配usb request block */
    uk_urb = usb_alloc_urb(0, GFP_KERNEL);
    /* 使用"3要素设置urb" */
    usb_fill_int_urb(uk_urb, dev, pipe, usb_buf, len, usbmouse_as_key_irq, NULL, endpoint->bInterval);
    uk_urb->transfer_dma = usb_buf_phys;
    uk_urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;

    /* 使用URB */
    usb_submit_urb(uk_urb, GFP_KERNEL);
    
    return 0;
}

static void usbmouse_as_key_disconnect(struct usb_interface *intf)
{
    struct usb_device *dev = interface_to_usbdev(intf);

    //printk("disconnect usbmouse!\n");
    usb_kill_urb(uk_urb);
    usb_free_urb(uk_urb);

    usb_buffer_free(dev, len, usb_buf, usb_buf_phys);
    input_unregister_device(uk_dev);
    input_free_device(uk_dev);
}

/* 1. 分配/设置usb_driver */
static struct usb_driver usbmouse_as_key_driver = {
    .name        = "usbmouse_as_key_",
    .probe        = usbmouse_as_key_probe,
    .disconnect    = usbmouse_as_key_disconnect,
    .id_table    = usbmouse_as_key_id_table,
};


static int usbmouse_as_key_init(void)
{
    /* 2. 注册 */
    usb_register(&usbmouse_as_key_driver);
    return 0;
}

static void usbmouse_as_key_exit(void)
{
    usb_deregister(&usbmouse_as_key_driver);    
}

module_init(usbmouse_as_key_init);
module_exit(usbmouse_as_key_exit);

MODULE_LICENSE("GPL");