usb触摸屏驱动 - usbtouchscreen

驱动编译：

目前的kernel中都是自带了usbtouchscreen驱动的，我的版本3.1.10

源码位于：/kernel/drivers/input/touchscreen/usbtouchscreen.c

从这个路径可以看出所属驱动分支，我这边平台本身是没放开的，并没有编译进kernel，谁会想到触摸电视呢~

可以在make menuconfig之后，通过Device Drivers——>Input device support——>Touchscreens——>USB Touchscreen Driver 然后选取需要的touchscreen类型

通过查看相关目录下的的Kconfig Makefile，可参考：Kernel 编译配置机制

注册usb驱动：

熟悉linux驱动的都知道模块入口：module_init(usbtouch_init) ，这里看下这个init：

static int __init usbtouch_init(void)
{return usb_register(&usbtouch_driver);  //调用了usb 核心的注册函数，传入的是一个usb_driver结构体指针
} int __init usbtouch_init(void)
{return usb_register(&usbtouch_driver);  //调用了usb 核心的注册函数，传入的是一个usb_driver结构体指针
}

usb_register实现在/kernel/include/linux/usb.h中：

static inline int usb_register(struct usb_driver *driver)
{return usb_register_driver(driver, THIS_MODULE, KBUILD_MODNAME);//这里再往后就是usb核心驱动的事，注册这个module驱动到usb总线上
} inline int usb_register(struct usb_driver *driver)
{return usb_register_driver(driver, THIS_MODULE, KBUILD_MODNAME);//这里再往后就是usb核心驱动的事，注册这个module驱动到usb总线上
}

这里必须是要先注册的总线，当一个USB设备被插入的时候，USB设备驱动，也就是usb_generic_driver会跟USB设备交互，得到其所有的各种描述符，并为每个接口都定义成为一个device，之后再加载到usb_bus上，让其去匹配其对应的接口驱动程序,有兴趣可以去看下/kernel/drivers/base/bus.c中的 bus_for_each_drv

函数。

这里注册到总线的接口驱动就是 usbtouch_driver

usbtouch_driver：

这个usb_driver类型的变量 usbtouch_driver就是整个usbtouchscreen的灵魂核心,可以在上面说到的usb.h中查看usb_driver结构原型，

这里usbtouch_driver使用了部分接口：

static struct usb_driver usbtouch_driver = {.name       = "usbtouchscreen", //driver name.probe      = usbtouch_probe,  //probe接口，用于总线上匹配检测到这个驱动对应的设备之后，/kernel/drivers/usb/core/driver.c中的usb_probe_interface调用到我们这个驱动的接口.disconnect = usbtouch_disconnect,  //与probe相反，断开的时候调用.suspend  = usbtouch_suspend, //usb 设备挂起.resume      = usbtouch_resume,  // 和上面挂起相反，唤醒.reset_resume  = usbtouch_reset_resume,  // 重置唤醒.id_table = usbtouch_devices, //支持的设备ID表.supports_autosuspend = 1,
};
 struct usb_driver usbtouch_driver = {.name     = "usbtouchscreen", //driver name.probe      = usbtouch_probe,  //probe接口，用于总线上匹配检测到这个驱动对应的设备之后，/kernel/drivers/usb/core/driver.c中的usb_probe_interface调用到我们这个驱动的接口.disconnect = usbtouch_disconnect,  //与probe相反，断开的时候调用.suspend  = usbtouch_suspend, //usb 设备挂起.resume      = usbtouch_resume,  // 和上面挂起相反，唤醒.reset_resume  = usbtouch_reset_resume,  // 重置唤醒.id_table = usbtouch_devices, //支持的设备ID表.supports_autosuspend = 1,
};

id_table：

首先可以关注一下 id_table 这个变量，代表支持的设备id列表，数据类型为：

struct usb_device_id {/* which fields to match against? */__u16      match_flags;/* Used for product specific matches; range is inclusive */__u16        idVendor;__u16      idProduct;__u16     bcdDevice_lo;__u16      bcdDevice_hi;/* Used for device class matches */__u8        bDeviceClass;__u8       bDeviceSubClass;__u8        bDeviceProtocol;/* Used for interface class matches */__u8      bInterfaceClass;__u8        bInterfaceSubClass;__u8     bInterfaceProtocol;/* not matched against */kernel_ulong_t  driver_info;
}; usb_device_id {/* which fields to match against? */__u16      match_flags;/* Used for product specific matches; range is inclusive */__u16        idVendor;__u16      idProduct;__u16     bcdDevice_lo;__u16      bcdDevice_hi;/* Used for device class matches */__u8        bDeviceClass;__u8       bDeviceSubClass;__u8        bDeviceProtocol;/* Used for interface class matches */__u8      bInterfaceClass;__u8        bInterfaceSubClass;__u8     bInterfaceProtocol;/* not matched against */kernel_ulong_t  driver_info;
};

这些设备信息会被上面说到的usb bus 来匹配对应的驱动，只有这里的信息跟usb设备驱动那边收集到的设备信息匹配上，才会调用进这个驱动.

目前已有的 id_table:

static const struct usb_device_id usbtouch_devices[] = {
#ifdef CONFIG_TOUCHSCREEN_USB_EGALAX/* ignore the HID capable devices, handled by usbhid */{USB_DEVICE_HID_CLASS(0x0eef, 0x0001), .driver_info = DEVTYPE_IGNORE},{USB_DEVICE_HID_CLASS(0x0eef, 0x0002), .driver_info = DEVTYPE_IGNORE},
...
#endif
...
};
 const struct usb_device_id usbtouch_devices[] = {
#ifdef CONFIG_TOUCHSCREEN_USB_EGALAX/* ignore the HID capable devices, handled by usbhid */{USB_DEVICE_HID_CLASS(0x0eef, 0x0001), .driver_info = DEVTYPE_IGNORE},{USB_DEVICE_HID_CLASS(0x0eef, 0x0002), .driver_info = DEVTYPE_IGNORE},
...
#endif
...
};

其中可以看到两个字节的十六进制数字，第一个代表idVendor 厂商ID，idProduct 产品ID ，这两个一般作为设备的标识.

driver_info：

像上面的 usbtouch_devices的数组中driver_info 设置为枚举值：

/* device types */
enum {DEVTYPE_IGNORE = -1,DEVTYPE_EGALAX,DEVTYPE_PANJIT,DEVTYPE_3M,DEVTYPE_ITM,DEVTYPE_ETURBO,DEVTYPE_GUNZE,DEVTYPE_DMC_TSC10,DEVTYPE_IRTOUCH,DEVTYPE_IDEALTEK,DEVTYPE_GENERAL_TOUCH,DEVTYPE_GOTOP,DEVTYPE_JASTEC,DEVTYPE_E2I,DEVTYPE_ZYTRONIC,DEVTYPE_TC45USB,DEVTYPE_NEXIO,
};
enum {DEVTYPE_IGNORE = -1,DEVTYPE_EGALAX,DEVTYPE_PANJIT,DEVTYPE_3M,DEVTYPE_ITM,DEVTYPE_ETURBO,DEVTYPE_GUNZE,DEVTYPE_DMC_TSC10,DEVTYPE_IRTOUCH,DEVTYPE_IDEALTEK,DEVTYPE_GENERAL_TOUCH,DEVTYPE_GOTOP,DEVTYPE_JASTEC,DEVTYPE_E2I,DEVTYPE_ZYTRONIC,DEVTYPE_TC45USB,DEVTYPE_NEXIO,
};

那么这些driver 的真正的info保存在哪里呢？在注册的时候，现在只是注册上去一个枚举数字而已，

真正有设备识别到的时候这些个枚举值就起到作用了！在下面的 usbtouch_probe会介绍！

usbtouch_probe：

在前面有稍微提到，usbtouchscreen驱动是怎么被映射到的，这个过程暂时不做深入，作为这个驱动中的第一个接入点就是usbtouch_probe.

static int usbtouch_probe(struct usb_interface *intf,const struct usb_device_id *id)
{struct usbtouch_usb *usbtouch;  //usbtouch 设备struct input_dev *input_dev;  //输入设备struct usb_endpoint_descriptor *endpoint;  //usb 的端点struct usb_device *udev = interface_to_usbdev(intf);  //从usb接口获取对应的设备struct usbtouch_device_info *type;   //这个就是上面说的真正的 driver info了endpoint = usbtouch_get_input_endpoint(intf->cur_altsetting);  //获取端点if (!endpoint)return -ENXIO;usbtouch = kzalloc(sizeof(struct usbtouch_usb), GFP_KERNEL);input_dev = input_allocate_device();  //分配内存，申请input 设备结构
...type = &usbtouch_dev_info[id->driver_info];   // 这里就用到了 上面说到的枚举值了， 真正的info 是放在这个数组里面的！
...usbtouch->irq = usb_alloc_urb(0, GFP_KERNEL);  //分配了一个urb 用于 获得触摸屏设备返回的触摸事件的数据，urb的概念可参考usb driverif (!usbtouch->irq) {dbg("%s - usb_alloc_urb failed: usbtouch->irq", __func__);goto out_free_buffers;}
...
//往下都是一些分配内存，input注册，初始化操作了input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS); //这里是就是input设备触摸坐标的初始化赋值了，为ABS 绝对坐标input_dev->keybit[BIT_WORD(BTN_TOUCH)] = BIT_MASK(BTN_TOUCH);input_set_abs_params(input_dev, ABS_X, type->min_xc, type->max_xc, 0, 0);input_set_abs_params(input_dev, ABS_Y, type->min_yc, type->max_yc, 0, 0);
...if (usb_endpoint_type(endpoint) == USB_ENDPOINT_XFER_INT)usb_fill_int_urb(usbtouch->irq, udev,usb_rcvintpipe(udev, endpoint->bEndpointAddress),usbtouch->data, type->rept_size,usbtouch_irq, usbtouch, endpoint->bInterval);elseusb_fill_bulk_urb(usbtouch->irq, udev,usb_rcvbulkpipe(udev, endpoint->bEndpointAddress),usbtouch->data, type->rept_size,usbtouch_irq, usbtouch);  //初始化urb的回调函数为 usbtouch_irqusbtouch->irq->dev = udev;usbtouch->irq->transfer_dma = usbtouch->data_dma;usbtouch->irq->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
...
}
int usbtouch_probe(struct usb_interface *intf,const struct usb_device_id *id)
{struct usbtouch_usb *usbtouch;  //usbtouch 设备struct input_dev *input_dev;  //输入设备struct usb_endpoint_descriptor *endpoint;  //usb 的端点struct usb_device *udev = interface_to_usbdev(intf);  //从usb接口获取对应的设备struct usbtouch_device_info *type;   //这个就是上面说的真正的 driver info了endpoint = usbtouch_get_input_endpoint(intf->cur_altsetting);  //获取端点if (!endpoint)return -ENXIO;usbtouch = kzalloc(sizeof(struct usbtouch_usb), GFP_KERNEL);input_dev = input_allocate_device();  //分配内存，申请input 设备结构
...type = &usbtouch_dev_info[id->driver_info];   // 这里就用到了 上面说到的枚举值了， 真正的info 是放在这个数组里面的！
...usbtouch->irq = usb_alloc_urb(0, GFP_KERNEL);  //分配了一个urb 用于 获得触摸屏设备返回的触摸事件的数据，urb的概念可参考usb driverif (!usbtouch->irq) {dbg("%s - usb_alloc_urb failed: usbtouch->irq", __func__);goto out_free_buffers;}
...
//往下都是一些分配内存，input注册，初始化操作了input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS); //这里是就是input设备触摸坐标的初始化赋值了，为ABS 绝对坐标input_dev->keybit[BIT_WORD(BTN_TOUCH)] = BIT_MASK(BTN_TOUCH);input_set_abs_params(input_dev, ABS_X, type->min_xc, type->max_xc, 0, 0);input_set_abs_params(input_dev, ABS_Y, type->min_yc, type->max_yc, 0, 0);
...if (usb_endpoint_type(endpoint) == USB_ENDPOINT_XFER_INT)usb_fill_int_urb(usbtouch->irq, udev,usb_rcvintpipe(udev, endpoint->bEndpointAddress),usbtouch->data, type->rept_size,usbtouch_irq, usbtouch, endpoint->bInterval);elseusb_fill_bulk_urb(usbtouch->irq, udev,usb_rcvbulkpipe(udev, endpoint->bEndpointAddress),usbtouch->data, type->rept_size,usbtouch_irq, usbtouch);  //初始化urb的回调函数为 usbtouch_irqusbtouch->irq->dev = udev;usbtouch->irq->transfer_dma = usbtouch->data_dma;usbtouch->irq->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
...
}

usbtouch_device_info:

这个就是上面driver_info 以及usbtouch_probe 中抽取的驱动模块的info数组，不同的usbtouchscreen 注册的时候就是注册了一个枚举值，这个值就是 usbtouch_dev_info数组的第几元素.

struct usbtouch_device_info {int min_xc, max_xc;int min_yc, max_yc;int min_press, max_press;int rept_size;/** Always service the USB devices irq not just when the input device is* open. This is useful when devices have a watchdog which prevents us* from periodically polling the device. Leave this unset unless your* touchscreen device requires it, as it does consume more of the USB* bandwidth.*/bool irq_always;void (*process_pkt) (struct usbtouch_usb *usbtouch, unsigned char *pkt, int len);  //这个函数指针是用来接收处理中断的。/** used to get the packet len. possible return values:* > 0: packet len* = 0: skip one byte* < 0: -return value more bytes needed*/int  (*get_pkt_len) (unsigned char *pkt, int len);int  (*read_data)   (struct usbtouch_usb *usbtouch, unsigned char *pkt);int  (*alloc)       (struct usbtouch_usb *usbtouch);int  (*init)     (struct usbtouch_usb *usbtouch);void (*exit)        (struct usbtouch_usb *usbtouch);
};
  int min_xc, max_xc;int min_yc, max_yc;int min_press, max_press;int rept_size;/** Always service the USB devices irq not just when the input device is* open. This is useful when devices have a watchdog which prevents us* from periodically polling the device. Leave this unset unless your* touchscreen device requires it, as it does consume more of the USB* bandwidth.*/bool irq_always;void (*process_pkt) (struct usbtouch_usb *usbtouch, unsigned char *pkt, int len);  //这个函数指针是用来接收处理中断的。/** used to get the packet len. possible return values:* > 0: packet len* = 0: skip one byte* < 0: -return value more bytes needed*/int  (*get_pkt_len) (unsigned char *pkt, int len);int  (*read_data)   (struct usbtouch_usb *usbtouch, unsigned char *pkt);int  (*alloc)      (struct usbtouch_usb *usbtouch);int  (*init)     (struct usbtouch_usb *usbtouch);void (*exit)        (struct usbtouch_usb *usbtouch);
};

usbtouch_dev_info

数组：

static struct usbtouch_device_info usbtouch_dev_info[] = {
#ifdef CONFIG_TOUCHSCREEN_USB_EGALAX[DEVTYPE_EGALAX] = {.min_xc        = 0x0,.max_xc      = 0x07ff,.min_yc       = 0x0,.max_yc      = 0x07ff,.rept_size    = 16,.process_pkt  = usbtouch_process_multi,//用于中断回调函数，用于处理中断，得到input的event，上传数据.get_pkt_len = egalax_get_pkt_len,.read_data    = egalax_read_data, //用于中断回调函数，用于读取数据},
#endif
...
#ifdef CONFIG_TOUCHSCREEN_USB_IRTOUCH[DEVTYPE_IRTOUCH] = {.min_xc      = 0x0,.max_xc      = 0x0fff,.min_yc       = 0x0,.max_yc      = 0x0fff,.rept_size    = 8,.read_data = irtouch_read_data,},
#endif
...
};
 struct usbtouch_device_info usbtouch_dev_info[] = {
#ifdef CONFIG_TOUCHSCREEN_USB_EGALAX[DEVTYPE_EGALAX] = {.min_xc        = 0x0,.max_xc      = 0x07ff,.min_yc       = 0x0,.max_yc      = 0x07ff,.rept_size    = 16,.process_pkt  = usbtouch_process_multi,//用于中断回调函数，用于处理中断，得到input的event，上传数据.get_pkt_len = egalax_get_pkt_len,.read_data    = egalax_read_data, //用于中断回调函数，用于读取数据},
#endif
...
#ifdef CONFIG_TOUCHSCREEN_USB_IRTOUCH[DEVTYPE_IRTOUCH] = {.min_xc      = 0x0,.max_xc      = 0x0fff,.min_yc       = 0x0,.max_yc      = 0x0fff,.rept_size    = 8,.read_data = irtouch_read_data,},
#endif
...
};

可以看到这个数组的成员都是以前面说到的注册枚举值来区分的！这些x，y 参数以及回调函数，都在上面说到的 usbtouch_probe 中被抽离出来使用.

usbtouch_irq:

这个函数作为中断响应函数，在上面的 usbtouch_probe中初始化，看下函数主要实现：

static void usbtouch_irq(struct urb *urb)
{
...usbtouch->type->process_pkt(usbtouch, usbtouch->data, urb->actual_length);
//这个type的类型就是 usbtouch_device_info，此时的process_pkt指针自然指向的是上面对应的函数，如果此时是触发的设备type为 DEVTYPE_EGALAX，那么这里调用的 usbtouch_process_multi
//如果此时是DEVTYPE_IRTOUCH 那么就是执行 usbtouch_process_pkt函数，因为usbtouch_probe中：
//  if (!type->process_pkt)
//      type->process_pkt = usbtouch_process_pkt;
...
}
q(struct urb *urb)
{
...usbtouch->type->process_pkt(usbtouch, usbtouch->data, urb->actual_length);
//这个type的类型就是 usbtouch_device_info，此时的process_pkt指针自然指向的是上面对应的函数，如果此时是触发的设备type为 DEVTYPE_EGALAX，那么这里调用的 usbtouch_process_multi
//如果此时是DEVTYPE_IRTOUCH 那么就是执行 usbtouch_process_pkt函数，因为usbtouch_probe中：
//  if (!type->process_pkt)
//      type->process_pkt = usbtouch_process_pkt;
...
}

接下来的都会调用到usbtouch_process_pkt中，通过type->read_data，和上面一样的指针读取，然后调用input_report_key发送，input_sync用于同步.

关于usbtouchscreen的驱动部分就分析到这里。