Linux驱动子系统之输入子系统

来源：互联网发布：nginx禁止某个ip访问编辑：程序博客网时间：2024/05/21 11:17

Gpio-keys是基于input架构实现的一个通用GPIO按键驱动。该驱动基于platform_driver架构，实现了驱动和设备分离，符合Linux设备驱动模型的思想。工程中的按键驱动我们一般都会基于gpio-keys来写，所以我们有必要对gpio_keys进行分析。

[gpio-keys驱动分析]

Gpio-keys的代码在drivers/input/keyboard/gpio_keys.c中，具体分析一下probe函数，probe函数会在platformdriver和platform device匹配上后被调用。

1.static int __devinit gpio_keys_probe(structplatform_device *pdev)
2.{
3.         structgpio_keys_platform_data *pdata = pdev->dev.platform_data;
4.         structgpio_keys_drvdata *ddata;
5.         structinput_dev *input;
6.         inti, error;
7.         intwakeup = 0;
8.
9.         /*kzalloc 对kmalloc的封装，会清0分配的空间*/
10.         ddata= kzalloc(sizeof(struct gpio_keys_drvdata) +
11.                            pdata->nbuttons* sizeof(struct gpio_button_data),
12.                            GFP_KERNEL);
13.
14.         /*分配一个input设备*/
15.         input= input_allocate_device();
16.         if(!ddata || !input) {
17.                   error= -ENOMEM;
18.                   gotofail1;
19.         }
20.
21.         platform_set_drvdata(pdev,ddata);
22.
23./* 设置input设备属性 */
24.         input->name= pdev->name;
25.         input->phys= "gpio-keys/input0";
26.         input->dev.parent= &pdev->dev;
27.
28.         input->id.bustype= BUS_HOST;
29.         input->id.vendor= 0x0001;
30.         input->id.product= 0x0001;
31.         input->id.version= 0x0100;
32.
33.         /*Enable auto repeat feature of Linux input subsystem */
34.         if(pdata->rep)
35.                   __set_bit(EV_REP,input->evbit);
36.
37.         ddata->input= input;
38.
39.         for(i = 0; i < pdata->nbuttons; i++) {
40.                   structgpio_keys_button *button = &pdata->buttons[i];
41.                   structgpio_button_data *bdata = &ddata->data[i];
42.                   intirq;
43.                   unsignedint type = button->type ?: EV_KEY;
44.
45.                   bdata->input= input;
46.                   bdata->button= button;
47.                   setup_timer(&bdata->timer,
48.                                gpio_keys_timer, (unsigned long)bdata);
49.                   /*初始化工作队列 */
50.                   INIT_WORK(&bdata->work,gpio_keys_report_event);
51.
52.                   /*申请GPIO口*/
53.error = gpio_request(button->gpio, button->desc ?:"gpio_keys");
54.                   if(error < 0) {
55.                            pr_err("gpio-keys:failed to request GPIO %d,"
56.                                     "error %d\n", button->gpio, error);
57.                            gotofail2;
58.                   }
59.                /* 把GPIO设为输入 */
60.                   error= gpio_direction_input(button->gpio);
61.                   if(error < 0) {
62.                            pr_err("gpio-keys:failed to configure input"
63.                                     "direction for GPIO %d, error %d\n",
64.                                     button->gpio,error);
65.                            gpio_free(button->gpio);
66.                            gotofail2;
67.                   }
68.                   /*获取GPIO对应的中断*/
69.                   irq= gpio_to_irq(button->gpio);
70.                   if(irq < 0) {
71.                            error= irq;
72.                            pr_err("gpio-keys:Unable to get irq number"
73.                                     "for GPIO %d, error %d\n",
74.                                     button->gpio,error);
75.                            gpio_free(button->gpio);
76.                            gotofail2;
77.                   }
78.                   /*注册中断 */
79.                   error= request_irq(irq, gpio_keys_isr,
80.                                         IRQF_SHARED |
81.                                         IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
82.                                         button->desc ? button->desc :"gpio_keys",
83.                                         bdata);
84.                   if(error) {
85.                            pr_err("gpio-keys:Unable to claim irq %d; error %d\n",
86.                                     irq,error);
87.                            gpio_free(button->gpio);
88.                            gotofail2;
89.                   }
90.
91.                   if(button->wakeup)
92.                            wakeup= 1;
93.
94.                   /*设置设备对事件的支持，比如设置对键1和键2的支持*/
95.                   input_set_capability(input,type, button->code);
96.         }
97.
98.         /*注册input设备*/
99.         error= input_register_device(input);
100.         if(error) {
101.                   pr_err("gpio-keys:Unable to register input device, "
102.                            "error:%d\n", error);
103.                   gotofail2;
104.         }
105.
106.         device_init_wakeup(&pdev->dev,wakeup);
107.
108.         return0;
109.         ……
110.         returnerror;
111.}

[中断服务例程]

1.static irqreturn_t gpio_keys_isr(int irq,void *dev_id)
2.{
3.         structgpio_button_data *bdata = dev_id;
4.         structgpio_keys_button *button = bdata->button;
5.
6.         BUG_ON(irq!= gpio_to_irq(button->gpio));
7.
8.         /*检测是否在platform device设置了去抖动www.linuxidc.com*/
9.if(button->debounce_interval)
10.                   mod_timer(&bdata->timer, /* 延迟msecs_to_jiffies(button->debounce_interval)个jiffies后执行schedule_work()*/
11.                            jiffies+ msecs_to_jiffies(button->debounce_interval));
12.         else
13.                   schedule_work(&bdata->work);
14.
15.         returnIRQ_HANDLED;
16.}

这里的中断被分成了上半部和下半部，上半部(中断处理例程)对中断进行了快速的相应，马上调度work上报事件信息：

1.static void gpio_keys_report_event(structwork_struct *work)
2.{
3.         structgpio_button_data *bdata =
4.                   container_of(work,struct gpio_button_data, work);
5.         structgpio_keys_button *button = bdata->button;
6.         structinput_dev *input = bdata->input;
7.         unsignedint type = button->type ?: EV_KEY;
8.         intstate = (gpio_get_value(button->gpio) ? 1 : 0) ^ button->active_low;
9.
10.         input_event(input,type, button->code, !!state);
11.         input_sync(input);
12.}

[两个结构体]

1.struct gpio_keys_button {
2.         /*Configuration parameters */
3.         intcode;            /* 输入事件代码(KEY_*, SW_*) */
4.         intgpio;             /* gpio口 */
5.         intactive_low; /* 低电平有效*/
6.         char*desc;      /* 功能描述 */
7.         inttype;            /* 输入事件类型(EV_KEY, EV_SW) */
8.         intwakeup;               /* configure thebutton as a wake-up source */
9.         intdebounce_interval;    /* 去抖动间隔，单位微秒*/
10.};
11.
12.struct gpio_keys_platform_data {
13.         structgpio_keys_button *buttons;
14.         intnbuttons;
15.         unsignedint rep:1;           /* enable inputsubsystem auto repeat */
16.};

到此基本上分析完了

[工程中的实现]

上面只是分析了gpio-keys的作用，但是我们要如何使用呢？下面是具体的platform device的实现：

1.static struct gpio_keys_button sc_buttons[]= {
2.    {
3.       .gpio   = S3C2410_GPG(0),   /* K1 */
4.       .code   = KEY_1,
5.       .desc   = "KEY1",
6.       .active_low = 1,
7.   },
8.    {
9.       .gpio   = S3C2410_GPG(3),   /* K2 */
10.       .code   = KEY_2,
11.       .desc   = "KEY2",
12.       .active_low = 1,
13.   },
14.    {
15.       .gpio   = S3C2410_GPG(5),   /* K3 */
16.       .code   = KEY_3,
17.        .desc = "KEY3",
18.       .active_low = 1,
19.   },
20.    {
21.       .gpio   = S3C2410_GPG(6),   /* K4 */
22.       .code   = KEY_4,
23.       .desc   = "KEY4",
24.       .active_low = 1,
25.   },
26.    {
27.       .gpio   = S3C2410_GPG(7),   /* K5 */
28.       .code   = KEY_5,
29.       .desc   = "KEY5",
30.       .active_low = 1,
31.   },
32.};
33.
34.static struct gpio_keys_platform_datasc_button_data = {
35.   .buttons    = sc_buttons,
36.   .nbuttons   =ARRAY_SIZE(sc_buttons),
37.};
38.
39.static struct platform_device sc_button_device= {
40.   .name   = "gpio-keys",   /* 与platform driver的名字要相同 */
41.   .id = -1,
42.   .dev    = {
43.       .platform_data =&sc_button_data,
44.    }
45.};
46.
47.static struct platform_device*mini2440_devices[] __initdata = {
48.         ……
49.   &sc_button_device,
50.};

最后记得把内核中对应的配置选项选上就OK。

本篇文章来源于 Linux公社网站(www.linuxidc.com) 原文链接：http://www.linuxidc.com/Linux/2011-11/47650p3.htm