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一直很好奇 USB 如此復(fù)雜的協(xié)議，在 Linux 中如何寫(xiě) USB 設(shè)備驅(qū)動(dòng)。剛好是微信所關(guān)注的一些 Linux 公眾號(hào)有提到 usb 骨架程序 usb-skeleton.c ，發(fā)現(xiàn)沒(méi)有想象中那么難。從網(wǎng)上查了一些相關(guān)的資料，先大概摸一下流程，就選了 USB 鼠標(biāo)的驅(qū)動(dòng)。有個(gè)大體的印象，再接著嘗試深入學(xué)習(xí)。USB設(shè)備那么流行，搞清楚了益處多多啊。哈哈。。。
#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>
/* for apple IDs */
#ifdef CONFIG_USB_HID_MODULE
#include "../hid-ids.h"
#endif
/*
* Version Information
*/
#define DRIVER_VERSION "v1.6"
#define DRIVER_AUTHOR "Vojtech Pavlik <vojtech@ucw.cz>"
#define DRIVER_DESC "USB HID Boot Protocol mouse driver"
#define DRIVER_LICENSE "GPL"
MODULE_AUTHOR(DRIVER_AUTHOR);
MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_LICENSE(DRIVER_LICENSE);
/*****************************
* 大體流程：
* 1、聲明USB設(shè)備列表
* 2、注冊(cè) USB 設(shè)備驅(qū)動(dòng)
* 3、USB 設(shè)備接入被檢測(cè)到
* 4、創(chuàng)建并填充 input 設(shè)備
* 5、設(shè)置 USB 數(shù)據(jù)獲取回調(diào)
* 6、通過(guò) input 上報(bào)相應(yīng)的鍵值
*****************************/
struct usb_mouse
{
char name[128];
char phys[64];
struct usb_device *usbdev;
struct input_dev *dev;
struct urb *irq;
signed char *data;
dma_addr_t data_dma;
};
/* 這個(gè)函數(shù)其實(shí)是回調(diào)函數(shù)而不是中斷 */
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;
// 檢查 USB 傳輸是否成功
switch (urb->status)
{
case 0: /* success */
break;
case -ECONNRESET: /* unlink */
case -ENOENT:
case -ESHUTDOWN:
return;
/* -EPIPE: should clear the halt */
default: /* error */
goto resubmit;
}
// 報(bào)告鼠標(biāo)按鍵情況 利用輸入子系統(tǒng)向系統(tǒng)發(fā)送鍵值
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: // 提交下次傳輸
status = usb_submit_urb (urb, GFP_ATOMIC);
if (status)
{
err ("can't resubmit intr, %s-%s/input0, status %d",
mouse->usbdev->bus->bus_name,
mouse->usbdev->devpath, status);
}
return ;
}
static int usb_mouse_open(struct input_dev *dev)
{
struct usb_mouse *mouse = input_get_drvdata(dev);
// 提交 URB 傳輸，這樣才會(huì)從 USB 鼠標(biāo)拿到數(shù)據(jù)
mouse->irq->dev = mouse->usbdev;
if (usb_submit_urb(mouse->irq, GFP_KERNEL))
return -EIO;
return 0;
}
static void usb_mouse_close(struct input_dev *dev)
{
struct usb_mouse *mouse = input_get_drvdata(dev);
// 停止傳輸
usb_kill_urb(mouse->irq);
}
static int usb_mouse_probe(struct usb_interface *intf, const struct usb_device_id *id)
{
// 設(shè)備描述
struct usb_device *dev = interface_to_usbdev(intf);
// 接口設(shè)置描述
struct usb_host_interface *interface;
// 端點(diǎn)描述
struct usb_endpoint_descriptor *endpoint;
struct usb_mouse *mouse;
struct input_dev *input_dev;
int pipe, maxp;
int error = -ENOMEM;
// 獲取當(dāng)前接口設(shè)置
interface = intf->cur_altsetting;
// 根據(jù) HID 規(guī)范，鼠標(biāo)只有一個(gè)端點(diǎn)(不包含0號(hào)控制端點(diǎn))
if (interface->desc.bNumEndpoints != 1)
return -ENODEV;
// 獲取端點(diǎn) 0 描述符
endpoint = &interface->endpoint[0].desc;
// 根據(jù) HID 規(guī)范，鼠標(biāo)唯一的端點(diǎn)應(yīng)為中斷端點(diǎn)并且為輸入的斷點(diǎn)
if (!usb_endpoint_is_int_in(endpoint))
return -ENODEV;
// 生成中斷管道
pipe = usb_rcvintpipe(dev, endpoint->bEndpointAddress);
// 返回該端點(diǎn)能夠傳輸?shù)淖畲蟮陌L(zhǎng)度，鼠標(biāo)的返回的最大數(shù)據(jù)包為 4 字節(jié)
maxp = usb_maxpacket(dev, pipe, usb_pipeout(pipe));
// 創(chuàng)建 input 設(shè)備
mouse = kzalloc(sizeof(struct usb_mouse), GFP_KERNEL);
input_dev = input_allocate_device();
if (!mouse || !input_dev)
goto fail1;
// 申請(qǐng)內(nèi)存空間用于數(shù)據(jù)傳輸, data 為指向該空間的地址
mouse->data = usb_alloc_coherent(dev, 8, GFP_ATOMIC, &mouse->data_dma);
if (!mouse->data)
goto fail1;
// 分配 URB
mouse->irq = usb_alloc_urb(0, GFP_KERNEL);
if (!mouse->irq)
goto fail2;
// 保存 USB 設(shè)備和 input 設(shè)備
mouse->usbdev = dev;
mouse->dev = input_dev;
// 這里拷貝字符串主要是為給輸入子系統(tǒng)命名的
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 用來(lái)獲取 USB 設(shè)備在 Sysfs 中的路徑
usb_make_path(dev, mouse->phys, sizeof(mouse->phys));
strlcat(mouse->phys, "/input0", sizeof(mouse->phys));
// 輸入設(shè)備驅(qū)動(dòng)
input_dev->name = mouse->name;
input_dev->phys = mouse->phys;
usb_to_input_id(dev, &input_dev->id);
input_dev->dev.parent = &intf->dev;
// 聲明此輸出設(shè)備所具有的特性，如按鍵、坐標(biāo)值等
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);
input_dev->open = usb_mouse_open; // 當(dāng)上層打開(kāi)時(shí)，會(huì)啟動(dòng)USB控制器從USB鼠標(biāo)中取數(shù)據(jù)
input_dev->close = usb_mouse_close; // 當(dāng)上層關(guān)閉時(shí)，會(huì)停止USB控制器從USB鼠標(biāo)中取數(shù)據(jù)
// 初始化中斷 URB
// pipe:取數(shù)據(jù)的地方 mouse->data:數(shù)據(jù)存放地方
// 當(dāng)從 USB 取完數(shù)據(jù)之后，調(diào)用 usb_mouse_irq()
usb_fill_int_urb(mouse->irq, dev, pipe, mouse->data, (maxp > 8 ? 8 : maxp), usb_mouse_irq, mouse, endpoint->bInterval);
// DMA 相關(guān)
mouse->irq->transfer_dma = mouse->data_dma;
// USB控制器自帶 transfer_dma 所以需要設(shè)置 URB_NO_TRANSFER_DMA_MAP 標(biāo)志，告知 HCD 不需要做 DMA 映射
mouse->irq->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
// 將 mouse 指針保存到 intf 的 dev 成員中
error = input_register_device(mouse->dev);
if (error)
goto fail3;
// 將 mouse 指針保存到 intf 的 dev 成遠(yuǎn)中
usb_set_intfdata(intf, mouse);
return 0;
fail3:
usb_free_urb(mouse->irq);
fail2:
usb_free_coherent(dev, 8, mouse->data, mouse->data_dma);
fail1:
input_free_device(input_dev);
kfree(mouse);
return error;
}
static void usb_mouse_disconnect(struct usb_interface *intf)
{
struct usb_mouse *mouse = usb_get_intfdata (intf);
// 當(dāng) USB 鼠標(biāo)被拔掉之后，需要釋放 USB 和 input
usb_set_intfdata(intf, NULL);
if (mouse)
{
usb_kill_urb(mouse->irq);
input_unregister_device(mouse->dev);
usb_free_urb(mouse->irq);
usb_free_coherent(interface_to_usbdev(intf), 8, mouse->data, mouse->data_dma);
kfree(mouse);
}
}
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 */
};
MODULE_DEVICE_TABLE (usb, usb_mouse_id_table);
static struct usb_driver usb_mouse_driver =
{
.name = "usbmouse",
.probe = usb_mouse_probe, // 當(dāng)檢測(cè)到USB鼠標(biāo)接入之后會(huì)進(jìn)行準(zhǔn)備工作
.disconnect = usb_mouse_disconnect, // USB 設(shè)備拔出
.id_table = usb_mouse_id_table, // USB 設(shè)備列表
};
// 注冊(cè)USB設(shè)備驅(qū)動(dòng)
module_usb_driver(usb_mouse_driver);
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