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46.Linux-分析rc红外遥控平台驱动框架,修改内核…

2018-10-14 10:49:13来源：博客园阅读 ()

内核版本 : Linux 3.10.14
rc红外接收类型: GPIO 类型的NEC红外编码

本章内容

1) rc体系结构分析
2) 分析红外platform_driver平台驱动框架
3) 分析内核自带的NEC红外解码过程
4) 修改内核自带的NEC红外解码BUG,实现按键重复按下

下章内容

1) 自己创建一个红外platform_device平台设备
2) 试验

在分析之前,先来复习下NEC红外编码的发送波形(在后面分析NEC解码会用到)

基本数据格式如下:

如果一直按住一个按钮时,会每隔100ms一直发送引导重复码.

一个完整的数据波形如下所示:

1.rc体系结构分析

rc相关文件位于kernel\drivers\media\rc

1.1首先来看kernel\drivers\media\rc\Makefile

如上图所示,由于我们板子上的红外接收编码是NEC格式,并且是GPIO类型

所以Make menuconfig配置宏:

  ->Device Drivers                                                                                           
    -> Multimedia support (MEDIA_SUPPORT [=y])                                                               
       -> Remote controller decoders (RC_DECODERS [=y])
            [*]   Enable IR raw decoder for the NEC protocol  
                 //选择NEC协议, ,使CONFIG_IR_NEC_DECODER=y

  ->Device Drivers                                                                                           
    -> Multimedia support (MEDIA_SUPPORT [=y])                                                               
        -> Remote Controller devices (RC_DEVICES [=y])
             [*]   GPIO IR remote control         
                //选择GPIO接收类型,使CONFIG_IR_GPIO_CIR=y

1.2然后在drivers\media\rc\keymaps里存了各种不同的键映射文件

先来看看drivers\media\rc\keymaps\Makefile:

如上图所示,可以看到把keymaps文件夹里的文件全部包含了.

它们用途在于:

1) 当内核解码后,通过我们红外平台设备的dev.platform_data里map_name成员去匹配这些文件.

其中红外平台设备platform_data对应的结构体为:

struct gpio_ir_recv_platform_data {
 int          gpio_nr;          //红外接收管对应的管脚
 bool         active_low;      //数据是否低电平有效
 u64          allowed_protos;  //该红外允许接收的编码协议,比如有NEC, SANYO, RC5等,可以填0,表示支持所有
 const char       *map_name;
           //该红外接收管对应的键值映射表名,内核会通过该名字去匹配keymaps文件夹里的编码对应的文件.从而注册该文件的键值映射表,以后解出来的编码则去找该键值映射表
};

2) 找到对应的文件,然后便通过该文件里的rc_map_list匹配编码

我们以rc-trekstor.c文件为例,该文件内容如下所示:

3)如果匹配到支持接收的编码,便会上报input事件按键.

PS: 在下章创建红外平台设备时,会详细讲解如何使用

2.分析红外platform_driver平台驱动框架

我们选择的是CONFIG_IR_GPIO_CIR宏,所以接下来分析GPIO类型的rc驱动框架,该宏对应的驱动文件为:

2.1 分析gpio-ir-recv.c的init入口函数

如上图所示,其中module_platform_driver()宏定义位于platform_device.h

最终module_platform_driver(gpio_ir_recv_driver)展开后等于:

static int __init gpio_ir_recv_driver_init(void)
{
        return platform_driver_register(&gpio_ir_recv_driver);
}
module_init(gpio_ir_recv_driver_init);
//…

该平台驱动的.name定义如下所示:

 #define GPIO_IR_DRIVER_NAME  "gpio-rc-recv"

所以我们后面创建红外platform_device平台设备时, .name也要写成"gpio-rc-recv"

2.2 分析gpio-ir-recv.c的probe函数

PS:在probe函数里,主要是获取平台设备pdev->dev.platform_data内容.该内容在1.2小结讲解过了.

代码如下:

static int gpio_ir_recv_probe(struct platform_device *pdev)
{
         struct gpio_rc_dev *gpio_dev;
         struct rc_dev *rcdev;
         const struct gpio_ir_recv_platform_data *pdata =pdev->dev.platform_data;  
                         //获取gpio_ir_recv_platform_data结构体

         int rc;
         //… …
         if (pdata->gpio_nr < 0)            //判断管脚有效性
                  return -EINVAL;

         gpio_dev = kzalloc(sizeof(struct gpio_rc_dev), GFP_KERNEL);
         if (!gpio_dev)
                  return -ENOMEM;
         rcdev = rc_allocate_device();
         if (!rcdev) {
                  rc = -ENOMEM;
                  goto err_allocate_device;
         }

         rcdev->priv = gpio_dev;
         rcdev->driver_type = RC_DRIVER_IR_RAW;
         rcdev->input_name = GPIO_IR_DEVICE_NAME;
         rcdev->input_phys = GPIO_IR_DEVICE_NAME "/input0";
         rcdev->input_id.bustype = BUS_HOST;
         rcdev->input_id.vendor = 0x0001;
         rcdev->input_id.product = 0x0001;
         rcdev->input_id.version = 0x0100;
         rcdev->dev.parent = &pdev->dev;
         rcdev->driver_name = GPIO_IR_DRIVER_NAME;
         if (pdata->allowed_protos)
                  rcdev->allowed_protos = pdata->allowed_protos;
         else
                  rcdev->allowed_protos = RC_BIT_ALL;         // allowed_protos==0,表示支持所有协议类型
         rcdev->map_name = pdata->map_name ?: RC_MAP_EMPTY; 

         gpio_dev->rcdev = rcdev;                                
         gpio_dev->gpio_nr = pdata->gpio_nr;
         gpio_dev->active_low = pdata->active_low;

         rc = gpio_request(pdata->gpio_nr, "gpio-ir-recv");               //申请IO管脚
         if (rc < 0)
                  goto err_gpio_request;
         rc  = gpio_direction_input(pdata->gpio_nr);                        //设置为输入
         if (rc < 0) 
                  goto err_gpio_direction_input;

         rc = rc_register_device(rcdev);
         if (rc < 0) {
                  dev_err(&pdev->dev, "failed to register rc device\n");
                  goto err_register_rc_device;
         }
         platform_set_drvdata(pdev, gpio_dev);

         rc = request_any_context_irq(gpio_to_irq(pdata->gpio_nr),
                                   gpio_ir_recv_irq,
                          IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING,
                                            "gpio-ir-recv-irq", gpio_dev);                 
                 //创建gpio_ir_recv_irq中断函数,为上下沿触发
         return 0;
        //… …
}

接下来,我们来看看gpio_ir_recv_irq()函数,看看如何实现解码的

2.3 分析gpio-ir-recv.c的gpio_ir_recv_irq函数

static irqreturn_t gpio_ir_recv_irq(int irq, void *dev_id)
{
         struct gpio_rc_dev *gpio_dev = dev_id;
         int gval;
         int rc = 0;
         enum raw_event_type type = IR_SPACE; //默认定义类型为IR_SPACE (红外接收的间隔信号)

         gval = gpio_get_value_cansleep(gpio_dev->gpio_nr);         //获取GPIO的值
         if (gval < 0)
                  goto err_get_value;
         if (gpio_dev->active_low)               //低电平有效
                  gval = !gval;                       //取反
         if (gval == 1)
                  type = IR_PULSE;                //收到的是脉冲信号

         rc = ir_raw_event_store_edge(gpio_dev->rcdev, type);  //通过内核时间,计算出当前波形的持续时间,并保存
         if (rc < 0)
                  goto err_get_value;

         ir_raw_event_handle(gpio_dev->rcdev);               //启动内核解码对应的线程,来处理波形
err_get_value:
         return IRQ_HANDLED;
}

接下来分析ir_raw_event_handle()函数如何处理波形的.

2.4 gpio_ir_recv_irq ()->ir_raw_event_handle()函数

该函数如下所示:

如上图所示,最终会唤醒一个线程,该线程对应的函数为ir_raw_event_thread():

static int ir_raw_event_thread(void *data)
{
         struct ir_raw_handler *handler;                    
         … …
        list_for_each_entry(handler, &ir_raw_handler_list, list)     
          // ir_raw_handler_list: 存储内核里注册的各个解码协议ir_raw_handler结构体,比如NEC, SANYO, RC5等
          handler->decode(raw->dev, ev);                     //调用解码函数    
         … …
};

2.5 接下来,我们看看解码文件是如何添加到ir_raw_handler_list表的

由于我们选择的是NEC协议(CONFIG_IR_NEC_DECODER=y),所以以/drivers/media/rc/ir-nec-decoder.c为例

1)首先查看ir-nec-decoder.c的init函数:

如上图所示,可以看到通过ir_raw_handler_register()来注册.

2) 然后ir_raw_handler_register()里,则将该nec_handler添加到ir_raw_handler_list表:

3.接下来,我们来分析ir_nec_decode()解码函数如何解码的.

3.1分析ir_nec_decode()解码函数

static int ir_nec_decode(struct rc_dev *dev, struct ir_raw_event ev)
{
         struct nec_dec *data = &dev->raw->nec;
         u32 scancode;
         u8 address, not_address, command, not_command;
         bool send_32bits = false;

         if (!(dev->enabled_protocols & RC_BIT_NEC))              //判断协议是否支持
                  return 0;
         //… …
         switch (data->state) {

         case STATE_INACTIVE:
                  if (!ev.pulse)
                          break;

                  if (eq_margin(ev.duration, NEC_HEADER_PULSE, NEC_UNIT * 2)) {           //判断ev.duration 是否等于9ms头引导码
                          data->is_nec_x = false;           //标记当前格式不是NECX编码格式
                          data->necx_repeat = false;
                  } else if (eq_margin(ev.duration, NECX_HEADER_PULSE, NEC_UNIT / 2)) //另一种不常见的NECX引导码
                          data->is_nec_x = true;                     //标记是NECX编码格式
                  else
                          break;

                  data->count = 0;
                  data->state = STATE_HEADER_SPACE;  //进入判断引导码间隔值,是4.5ms还是2.25ms ?           
                  return 0;

         case STATE_HEADER_SPACE:
                  if (ev.pulse)
                          break;

                  if (eq_margin(ev.duration, NEC_HEADER_SPACE, NEC_UNIT)) {    //如果ev.duration=4.5ms  间隔引导码
                          data->state = STATE_BIT_PULSE;                      //进入解析32bit模式
                          return 0; 
                  } else if (eq_margin(ev.duration, NEC_REPEAT_SPACE, NEC_UNIT / 2)) {  //如果ev.duration=2.5ms  ,表示重复引导码
                          if (!dev->keypressed) {                 //dev->keypressed是松开的,则放弃(这里有BUG,后面会分析到)
                                   IR_dprintk(1, "Discarding last key repeat: event after key up\n");
                          } else {
                                   rc_repeat(dev);               //dev->keypressed是未松开,则上报事件
                                   IR_dprintk(1, "Repeat last key\n");
                                   data->state = STATE_TRAILER_PULSE;
                          }
                          return 0;
                  }
                  break;

         case STATE_BIT_PULSE:                                    //接收数据位的脉冲数据
                  if (!ev.pulse)
                          break;
                  if (!eq_margin(ev.duration, NEC_BIT_PULSE, NEC_UNIT / 2))         //不等于0.56ms,则忽略掉
                          break;

                  data->state = STATE_BIT_SPACE;                            //等于0.56ms,接下来进入STATE_BIT_SPACE,开始解析数据bit
                  return 0;

         case STATE_BIT_SPACE:         
                  if (ev.pulse)
                          break;

                  if (data->necx_repeat && data->count == NECX_REPEAT_BITS &&
                          geq_margin(ev.duration,
                          NEC_TRAILER_SPACE, NEC_UNIT / 2)) {                //解析NECX编码格式
                                   IR_dprintk(1, "Repeat last key\n");
                                   rc_repeat(dev);
                                   data->state = STATE_INACTIVE;
                                   return 0;

                  } else if (data->count > NECX_REPEAT_BITS)
                          data->necx_repeat = false;

                  data->bits <<= 1;
                  if (eq_margin(ev.duration, NEC_BIT_1_SPACE, NEC_UNIT / 2))          // 1.68ms  数据1
                          data->bits |= 1;
                  else if (!eq_margin(ev.duration, NEC_BIT_0_SPACE, NEC_UNIT / 2)) // 既不等于1.68ms,也不等于0.56ms,则是无效数据
                          break;
                  data->count++;

                  if (data->count == NEC_NBITS)                             //data->count == 32,则表示数据接收完成
                          data->state = STATE_TRAILER_PULSE;
                  else
                          data->state = STATE_BIT_PULSE;
                  return 0;

         case STATE_TRAILER_PULSE:
                  if (!ev.pulse)
                          break;
                  if (!eq_margin(ev.duration, NEC_TRAILER_PULSE, NEC_UNIT / 2))
                          break;
                  data->state = STATE_TRAILER_SPACE;
                  return 0;

         case STATE_TRAILER_SPACE:
                  if (ev.pulse)
                          break;

                  if (!geq_margin(ev.duration, NEC_TRAILER_SPACE, NEC_UNIT / 2))
                          break;

                  address     = bitrev8((data->bits >> 24) & 0xff);                        
                  not_address = bitrev8((data->bits >> 16) & 0xff);
                  command            = bitrev8((data->bits >>  8) & 0xff);
                  not_command = bitrev8((data->bits >>  0) & 0xff);

                  if ((command ^ not_command) != 0xff) {                    //解析数据
                          IR_dprintk(1, "NEC checksum error: received 0x%08x\n",
                                      data->bits);
                          send_32bits = true;
                  }

                  if (send_32bits) {
                          /* NEC transport, but modified protocol, used by at
                           * least Apple and TiVo remotes */
                          scancode = data->bits;
                          IR_dprintk(1, "NEC (modified) scancode 0x%08x\n", scancode);
                  } else if ((address ^ not_address) != 0xff) {
                          /* Extended NEC */
                          scancode = address     << 16 |
                                      not_address <<  8 |
                                      command;
                          IR_dprintk(1, "NEC (Ext) scancode 0x%06x\n", scancode);
                  } else {
                          /* Normal NEC */
                          scancode = address << 8 | command;
                          IR_dprintk(1, "NEC scancode 0x%04x\n", scancode);
                  }

                  if (data->is_nec_x)
                          data->necx_repeat = true;

                  rc_keydown(dev, scancode, 0);              //通过scancode编码来上报按键事件
                  data->state = STATE_INACTIVE;
                  return 0;
         }
    //… …
}

3.2接下来分析ir_nec_decode ()->rc_keydown()如何通过scancode编码来上报按键事件

void rc_keydown(struct rc_dev *dev, int scancode, u8 toggle)
{
         unsigned long flags;
         u32 keycode = rc_g_keycode_from_table(dev, scancode); //从键映射表里找到编码对应的键值

         spin_lock_irqsave(&dev->keylock, flags);

         if(keycode){                               //如果找到键值
                  ir_do_keydown(dev, scancode, keycode, toggle); //上报按键事件

                  if (dev->keypressed) {       //如果是按下,则启动timer_keyup定时器, IR_KEYPRESS_TIMEOUT(20ms)后上报key松开事件
                          dev->keyup_jiffies = jiffies + msecs_to_jiffies(IR_KEYPRESS_TIMEOUT);
                          mod_timer(&dev->timer_keyup, dev->keyup_jiffies);
                  }
         }else{
                  dev->last_scancode = 0;
                  dev->last_toggle = 0;
                  dev->last_keycode = 0;
         }
         spin_unlock_irqrestore(&dev->keylock, flags);
}

上个函数里的dev->timer_keyup定时器对应的函数为ir_timer_keyup(),该函数会去调用一次ir_do_keyup()函数,上报key松开事件,该函数如下:

如上图所示,我们发现dev->keypressed = false,这就是解码函数出现的BUG:

1)比如当遥控器当按下按键时,会上报一次按键按下事件,并启动20ms定时器,用来自动上报按键自动按起事件,并标记dev->keypressed = false.

2)然后,如果遥控器一直按下不松手的话,会隔110ms发送一次9ms+2.25ms重复引导码

3) 然后内核将会调用ir_nec_decode()进行解码2.25ms

4. 修改ir_nec_decode()函数

接下来,我们修改ir_nec_decode()函数,实现按键重复按下,并实现rc_map->repeat_key.

为什么要实现rc_map->repeat_key？

因为rc_map->scan里存储的键值表仅仅表示可支持按下的按键, 而rc_map->repeat_key里存储的才是表示可重复按下的按键.

修改后的代码如下所示:

static int ir_nec_decode(struct rc_dev *dev, struct ir_raw_event ev)
{
    struct nec_dec *data = &dev->raw->nec;
     u32 scancode=0;
    u8 address, not_address, command, not_command;
    bool send_32bits = false;
    static int es9038_c28=0,es9038_c29=0,es9038_c30=0,es9038_c31=0;

    if (!(dev->enabled_protocols & RC_BIT_NEC))
       return 0;

    if (!is_timing_event(ev)) {
       if (ev.reset)
           data->state = STATE_INACTIVE;
       return 0;
    }

    IR_dprintk(2, "NEC decode started at state %d (%uus %s)\n",
          data->state, TO_US(ev.duration), TO_STR(ev.pulse));

    switch (data->state) {

    case STATE_INACTIVE:
       if (!ev.pulse)
           break;

       if (eq_margin(ev.duration, NEC_HEADER_PULSE, NEC_UNIT * 2)) {
           data->is_nec_x = false;
           data->necx_repeat = false;
       } else if (eq_margin(ev.duration, NECX_HEADER_PULSE, NEC_UNIT / 2))
       {   data->is_nec_x = true;
       }
       else
       break;

       data->count = 0;
       data->state = STATE_HEADER_SPACE;
       return 0;

    case STATE_HEADER_SPACE:
       if (ev.pulse)
           break;

       if (eq_margin(ev.duration, NEC_HEADER_SPACE, NEC_UNIT)) {
           data->state = STATE_BIT_PULSE;
           return 0;
       } else if (eq_margin(ev.duration, NEC_REPEAT_SPACE, NEC_UNIT / 2)) {       //处理重复编码

           data->state = STATE_TRAILER_SPACE;
           IR_dprintk(1, "Discarding last key repeat: event after key up\n");
           return 0;
       }
       else
           break;

    case STATE_BIT_PULSE:
       if (!ev.pulse)
           break;
       if (!eq_margin(ev.duration, NEC_BIT_PULSE, NEC_UNIT / 2))
           break;

       data->state = STATE_BIT_SPACE;
       return 0;

    case STATE_BIT_SPACE:
       if (ev.pulse)
           break;

       if (data->necx_repeat && data->count == NECX_REPEAT_BITS &&
           geq_margin(ev.duration,
           NEC_TRAILER_SPACE, NEC_UNIT / 2)) {
              IR_dprintk(1, "Repeat last key\n");
              rc_repeat(dev);
              data->state = STATE_INACTIVE;
              return 0;
       } else if (data->count > NECX_REPEAT_BITS)
           data->necx_repeat = false;

       data->bits <<= 1;

       if (eq_margin(ev.duration, NEC_BIT_1_SPACE, NEC_UNIT / 2))
           data->bits |= 1;

       else if (!eq_margin(ev.duration, NEC_BIT_0_SPACE, NEC_UNIT / 2))
           break;

       data->count++;

       if (data->count == NEC_NBITS)
           data->state = STATE_TRAILER_SPACE;
       else
           data->state = STATE_BIT_PULSE;
       return 0;

    case STATE_TRAILER_SPACE:
       {
       struct rc_map *rc_map = &dev->rc_map;
       struct rc_map_table *repeat_key = rc_map->repeat_key;
       unsigned int repeat_size = rc_map->repeat_size;         //获取 repeat_size,是否有支持重复按下的按键
           scancode=data->bits;

       if (!ev.pulse)
           break;

       if (!eq_margin(ev.duration, NEC_TRAILER_PULSE, NEC_UNIT / 2))
           break;
       printk("NEC scancode=0x%x\n",scancode);

       if(!scancode)
           break;
       if (data->is_nec_x)
           data->necx_repeat = true;

       rc_keydown(dev, scancode, 0);                 //上报事件
        if(repeat_key){               
           int i = 0;
           while(repeat_size){
              if(scancode == repeat_key[i].scancode){
                  break;
              }
              repeat_size--;
              i++;
           }  

        if(repeat_size==0)             //repeat_size==0,表示没找到有支持重复按键,则清空data->bits
              data->bits = 0;   }
        else
            data->bits = 0;

       return 0;
       }
    }

    IR_dprintk(1, "NEC decode failed at count %d state %d (%uus %s)\n",
          data->count, data->state, TO_US(ev.duration), TO_STR(ev.pulse));
    data->state = STATE_INACTIVE;
    return -EINVAL;
}