为linux添加自己的USB驱动

本来想为mini2440添加自己的USB驱动，然后通过手柄做一些控制，结果一开始就遇到自己写的驱动被抢占了，google了几天未果，在csdn发了一个求助帖（http://topic.csdn.net/u/20100926/15/b5c7fc3b-e4f9-4843-89d2-b88ea484b9f3.html?34584），deep_pro兄提供了一个方法，借助这个方法我打开了胜利之门。

1、驱动编写不用多说，不会的参照usb-skeleton.c。我的模块名是joystick，所以编译后的模块是joystick.ko。

2、安装模块。

insmod&dmesg发现自己驱动的probe没有被调用，下面被抢占的输出：

usb 5-1.4: new low speed USB device using uhci_hcd and address 6
usb 5-1.4: New USB device found, idVendor=0e8f, idProduct=0002
usb 5-1.4: New USB device strings: Mfr=1, Product=2, SerialNumber=0
usb 5-1.4: Product: BETOP USB GAMEPAD
usb 5-1.4: Manufacturer: GreenAsia Inc.
input: GreenAsia Inc. BETOP USB GAMEPAD as /devices/pci0000:00/0000:00:1d.0/usb5/5-1/5-1.4/5-1.4:1.0/input/input12
generic-usb 0003:0E8F:0002.0004: input,hidraw1: USB HID v1.10 Joystick [GreenAsia Inc. BETOP USB GAMEPAD] on usb-0000:00:1d.0-1.4/input0

之后deep_pro提供了一个方法（http://hi.baidu.com/deep_pro/blog/item/415ec217bdead20c4b90a77d.html），找到抢占设备的模块是usbhid，如果禁用此模块的话插入别的usbhid设备也用不了了，比如鼠标和键盘，所以只能让该模块忽略掉特定的设备，于是就开始读内核源码。刚开始我钻到了死角，一直在内核源码树下drivers/hid目录下找，把所有关于GREENASIA和PANTHERLORD的#define都注释了，还是未能解决，后来step out and look back，整理一下思路，钻到drivers/hid/usbhid里面找（之前也进去过，只是没怎么研究），用过函数嵌套关系一层一层回溯，终于到了顶点，在usbhid/hid-core.c里面的usbhid_probe（这是usbhid模块的probe函数）发现，如果不为设备调用hid_add_device，那该设备就不被usbhid模块抢占，所以我在usbhid模块的probe函数开头加了一段过滤代码，问题就解决了。

修改后的代码：

static struct usb_device_id ignored_list[] = {
{USB_DEVICE(USB_VENDOR_ID_GREENASIA, 0x0002)},
{ },
};
static int is_ignored_device(unsigned short idVendor, unsigned short idProduct)
{
int index;
for(index = 0;ignored_list[index].idVendor;index++)
{
if((ignored_list[index].idVendor == idVendor) && (ignored_list[index].idProduct == idProduct))
return 1;
}
return 0;
}
static int usbhid_probe(struct usb_interface *intf, const struct usb_device_id *id)
{
struct usb_host_interface *interface = intf->cur_altsetting;
struct usb_device *dev = interface_to_usbdev(intf);
struct usbhid_device *usbhid;
struct hid_device *hid;
unsigned int n, has_in = 0;
size_t len;
int ret;
dbg_hid("HID probe called for ifnum %d/n",
intf->altsetting->desc.bInterfaceNumber);
//ignore the device should not be handled by usbhid module
if(is_ignored_device(dev->descriptor.idVendor, dev->descriptor.idProduct))
{
printk("*** Device ignored ***/n");
printk("VendorID = %04X, ProductID = %04X/n", dev->descriptor.idVendor, dev->descriptor.idProduct);
printk("%s/n", dev->manufacturer);
printk("%s/n", dev->product);
//printk("%s/n", );
printk("**********************/n");
return -ENODEV;
}
for (n = 0; n < interface->desc.bNumEndpoints; n++)
if (usb_endpoint_is_int_in(&interface->endpoint
.desc))
has_in++;
if (!has_in) {
dev_err(&intf->dev, "couldn't find an input interrupt "
"endpoint/n");
return -ENODEV;
}
hid = hid_allocate_device();
if (IS_ERR(hid))
return PTR_ERR(hid);
usb_set_intfdata(intf, hid);
hid->ll_driver = &usb_hid_driver;
hid->hid_output_raw_report = usbhid_output_raw_report;
hid->ff_init = hid_pidff_init;
#ifdef CONFIG_USB_HIDDEV
hid->hiddev_connect = hiddev_connect;
hid->hiddev_disconnect = hiddev_disconnect;
hid->hiddev_hid_event = hiddev_hid_event;
hid->hiddev_report_event = hiddev_report_event;
#endif
hid->dev.parent = &intf->dev;
hid->bus = BUS_USB;
hid->vendor = le16_to_cpu(dev->descriptor.idVendor);
hid->product = le16_to_cpu(dev->descriptor.idProduct);
hid->name[0] = 0;
if (intf->cur_altsetting->desc.bInterfaceProtocol ==
USB_INTERFACE_PROTOCOL_MOUSE)
hid->type = HID_TYPE_USBMOUSE;
if (dev->manufacturer)
strlcpy(hid->name, dev->manufacturer, sizeof(hid->name));
if (dev->product) {
if (dev->manufacturer)
strlcat(hid->name, " ", sizeof(hid->name));
strlcat(hid->name, dev->product, sizeof(hid->name));
}
if (!strlen(hid->name))
snprintf(hid->name, sizeof(hid->name), "HID %04x:%04x",
le16_to_cpu(dev->descriptor.idVendor),
le16_to_cpu(dev->descriptor.idProduct));
usb_make_path(dev, hid->phys, sizeof(hid->phys));
strlcat(hid->phys, "/input", sizeof(hid->phys));
len = strlen(hid->phys);
if (len < sizeof(hid->phys) - 1)
snprintf(hid->phys + len, sizeof(hid->phys) - len,
"%d", intf->altsetting[0].desc.bInterfaceNumber);
if (usb_string(dev, dev->descriptor.iSerialNumber, hid->uniq, 64) <= 0)
hid->uniq[0] = 0;
usbhid = kzalloc(sizeof(*usbhid), GFP_KERNEL);
if (usbhid == NULL) {
ret = -ENOMEM;
goto err;
}
hid->driver_data = usbhid;
usbhid->hid = hid;
ret = hid_add_device(hid);
if (ret) {
if (ret != -ENODEV)
dev_err(&intf->dev, "can't add hid device: %d/n", ret);
goto err_free;
}
return 0;
err_free:
kfree(usbhid);
err:
hid_destroy_device(hid);
return ret;
}

ignored_list和is_ignored_device是我自己添加的。

重新编译usbhid模块和joystick模块，安装，插入手柄，输出如下：

usb 1-1: new low speed USB device using s3c2410-ohci and address 11

usb 1-1: New USB device found, idVendor=0e8f, idProduct=0002

usb 1-1: New USB device strings: Mfr=1, Product=2, SerialNumber=0

usb 1-1: Product: BETOP USB GAMEPAD

usb 1-1: Manufacturer: GreenAsia Inc.

usb 1-1: configuration #1 chosen from 1 choice

*** Device ignored ***

VendorID = 0E8F, ProductID = 0002

GreenAsia Inc.

BETOP USB GAMEPAD

**********************

*************** Probe for joystick. ****************

bNumEndpoints: 1

direction: (81)Endpoint type: intterupt

MaxPacketSize: 8

嘿嘿，自己驱动的probe函数被调用了，接着就可以和设备通信了，至于怎么通信，还是看usb-skeleton.c