USB驱动——鼠标驱动程序（中断传输）

    本文以 usbmouse.c 为例，简单分析usb鼠标驱动程序。

static int __init usb_mouse_init(void)
{
int retval = usb_register(&usb_mouse_driver);
if (retval == 0)
printk(KERN_INFO KBUILD_MODNAME ": " DRIVER_VERSION ":"
DRIVER_DESC "\n");
return retval;
}

    使用 usb_register 注册到内核的驱动程序都是对应于一个usb设备的接口（逻辑设备）。

static struct usb_driver usb_mouse_driver = {
.name		= "usbmouse",
.probe		= usb_mouse_probe,
.disconnect	= usb_mouse_disconnect,
.id_table	= usb_mouse_id_table,
};

    id_table 中指明了这个驱动程序支持哪些类型的接口

static struct usb_device_id usb_mouse_id_table [] = {
{ USB_INTERFACE_INFO(USB_INTERFACE_CLASS_HID, USB_INTERFACE_SUBCLASS_BOOT,
USB_INTERFACE_PROTOCOL_MOUSE) },
{ }	/* Terminating entry */
};

    USB_INTERFACE_INFO ，通过接口信息来匹配，内核里还有一些其它的宏，例如 USB_DEVICE ，使用它可以根据厂商ID、设备ID来匹配，让你的驱动程序仅仅支持某一个厂家的某一款设备。还有一些其它的匹配方法不再赘述。

    匹配成功之后，便会调用 probe 函数。

static int usb_mouse_probe(struct usb_interface *intf, const struct usb_device_id *id)
{
/* 得到设备 */
struct usb_device *dev = interface_to_usbdev(intf);

/* 一个接口的当前设置 */
struct usb_host_interface *interface;

/* 端点描述符 */
struct usb_endpoint_descriptor *endpoint;

struct usb_mouse *mouse;

/* 输入设备 */
struct input_dev *input_dev;
int pipe, maxp;
int error = -ENOMEM;

/* 获取接口的当前设置 */
interface = intf->cur_altsetting;

/* 获得当前设置的第一个端点的描述符，usb鼠标除了端点0就这一个端点 */
endpoint = &interface->endpoint[0].desc;

/* 获得端点对应的管道 */
pipe = usb_rcvintpipe(dev, endpoint->bEndpointAddress);

/* 返回这个端点的传输最大包大小 */
maxp = usb_maxpacket(dev, pipe, usb_pipeout(pipe));

/* 输入子系统 */
input_dev = input_allocate_device();

/* 用一个 usb_mouse 结构来保存 urb buffer irq 等信息 */
mouse = kzalloc(sizeof(struct usb_mouse), GFP_KERNEL);

/* 分配空间 */
mouse->data = usb_buffer_alloc(dev, 8, GFP_ATOMIC, &mouse->data_dma);

/* 分配urb */
mouse->irq = usb_alloc_urb(0, GFP_KERNEL);

mouse->usbdev = dev;
mouse->dev = input_dev;

/* 一些设备信息的拷贝，无关紧要 */
if (dev->manufacturer)
strlcpy(mouse->name, dev->manufacturer, sizeof(mouse->name));

if (dev->product) {
if (dev->manufacturer)
strlcat(mouse->name, " ", sizeof(mouse->name));
strlcat(mouse->name, dev->product, sizeof(mouse->name));
}

if (!strlen(mouse->name))
snprintf(mouse->name, sizeof(mouse->name),
"USB HIDBP Mouse %04x:%04x",
le16_to_cpu(dev->descriptor.idVendor),
le16_to_cpu(dev->descriptor.idProduct));

usb_make_path(dev, mouse->phys, sizeof(mouse->phys));
strlcat(mouse->phys, "/input0", sizeof(mouse->phys));

/* 输入子系统的一些设置 */
input_dev->name = mouse->name;
input_dev->phys = mouse->phys;
usb_to_input_id(dev, &input_dev->id);
input_dev->dev.parent = &intf->dev;

/* 设置支持哪些类型的事件。以及那些事件 */
input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_REL);
input_dev->keybit[BIT_WORD(BTN_MOUSE)] = BIT_MASK(BTN_LEFT) |
BIT_MASK(BTN_RIGHT) | BIT_MASK(BTN_MIDDLE);
input_dev->relbit[0] = BIT_MASK(REL_X) | BIT_MASK(REL_Y);
input_dev->keybit[BIT_WORD(BTN_MOUSE)] |= BIT_MASK(BTN_SIDE) |
BIT_MASK(BTN_EXTRA);
input_dev->relbit[0] |= BIT_MASK(REL_WHEEL);

input_set_drvdata(input_dev, mouse);

/* 输入设备的Open close 函数，open函数中会提交urb */
input_dev->open = usb_mouse_open;
input_dev->close = usb_mouse_close;

/* 填充中断传输类型的urb */
usb_fill_int_urb(mouse->irq, dev, pipe, mouse->data,
(maxp > 8 ? 8 : maxp),
usb_mouse_irq, mouse, endpoint->bInterval);
mouse->irq->transfer_dma = mouse->data_dma;
mouse->irq->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;

/* 注册输入设备 */
error = input_register_device(mouse->dev);

usb_set_intfdata(intf, mouse);
return 0;
}

static int usb_mouse_open(struct input_dev *dev)
{
struct usb_mouse *mouse = input_get_drvdata(dev);

mouse->irq->dev = mouse->usbdev;
if (usb_submit_urb(mouse->irq, GFP_KERNEL))
return -EIO;

return 0;
}

    open 输入设备的时候，urb 就被提交了。每次鼠标有信息要提交给usb主机时，就会调用到 

static void usb_mouse_irq(struct urb *urb)
{
struct usb_mouse *mouse = urb->context;
signed char *data = mouse->data;
struct input_dev *dev = mouse->dev;
int status;

switch (urb->status) {
case 0:			/* success */
break;
case -ECONNRESET:	/* unlink */
case -ENOENT:
case -ESHUTDOWN:
return;
/* -EPIPE:  should clear the halt */
default:		/* error */
goto resubmit;
}
/* 根据data里的内容，上报不同事件 */
input_report_key(dev, BTN_LEFT,   data[0] & 0x01);
input_report_key(dev, BTN_RIGHT,  data[0] & 0x02);
input_report_key(dev, BTN_MIDDLE, data[0] & 0x04);
input_report_key(dev, BTN_SIDE,   data[0] & 0x08);
input_report_key(dev, BTN_EXTRA,  data[0] & 0x10);

input_report_rel(dev, REL_X,     data[1]);
input_report_rel(dev, REL_Y,     data[2]);
input_report_rel(dev, REL_WHEEL, data[3]);

input_sync(dev);
resubmit:
status = usb_submit_urb (urb, GFP_ATOMIC);// 重新提交 urb
if (status)
err ("can't resubmit intr, %s-%s/input0, status %d",
mouse->usbdev->bus->bus_name,
mouse->usbdev->devpath, status);
}