- 內核版本 : Linux 3.10.14
- rc紅外接收類型: GPIO 類型的NEC紅外編碼
本章內容
- 1) rc體系結構分析
- 2) 分析紅外platform_driver平台驅動框架
- 3) 分析內核自帶的NEC紅外解碼過程
- 4) 修改內核自帶的NEC紅外解碼BUG,實現按鍵重復按下
下章內容
- 1) 自己創建一個紅外platform_device平台設備
- 2) 試驗
在分析之前,先來復習下NEC紅外編碼的發送波形(在后面分析NEC解碼會用到)
基本數據格式如下:
如果一直按住一個按鈕時,會每隔100ms一直發送引導重復碼.
一個完整的數據波形如下所示:
1.rc體系結構分析
rc相關文件位於kernel\drivers\media\rc
1.1首先來看kernel\drivers\media\rc\Makefile
如上圖所示,由於我們板子上的紅外接收編碼是NEC格式,並且是GPIO類型
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 //選擇NEC協議, ,使CONFIG_IR_NEC_DECODER=y ->Device Drivers -> Multimedia support (MEDIA_SUPPORT [=y]) -> Remote Controller devices (RC_DEVICES [=y]) [*] GPIO IR remote control //選擇GPIO接收類型,使CONFIG_IR_GPIO_CIR=y
1.2然后在drivers\media\rc\keymaps里存了各種不同的鍵映射文件
先來看看drivers\media\rc\keymaps\Makefile:
如上圖所示,可以看到把keymaps文件夾里的文件全部包含了.
它們用途在於:
1) 當內核解碼后,通過我們紅外平台設備的dev.platform_data里map_name成員去匹配這些文件.
其中紅外平台設備platform_data對應的結構體為:
struct gpio_ir_recv_platform_data { int gpio_nr; //紅外接收管對應的管腳 bool active_low; //數據是否低電平有效 u64 allowed_protos; //該紅外允許接收的編碼協議,比如有NEC, SANYO, RC5等,可以填0,表示支持所有 const char *map_name; //該紅外接收管對應的鍵值映射表名,內核會通過該名字去匹配keymaps文件夾里的編碼對應的文件.從而注冊該文件的鍵值映射表,以后解出來的編碼則去找該鍵值映射表 };
2) 找到對應的文件,然后便通過該文件里的rc_map_list匹配編碼
我們以rc-trekstor.c文件為例,該文件內容如下所示:
3)如果匹配到支持接收的編碼,便會上報input事件按鍵.
PS: 在下章創建紅外平台設備時,會詳細講解如何使用
2.分析紅外platform_driver平台驅動框架
我們選擇的是CONFIG_IR_GPIO_CIR宏,所以接下來分析GPIO類型的rc驅動框架,該宏對應的驅動文件為:
2.1 分析gpio-ir-recv.c的init入口函數
如上圖所示,其中module_platform_driver()宏定義位於platform_device.h
最終module_platform_driver(gpio_ir_recv_driver)展開后等於:
static int __init gpio_ir_recv_driver_init(void) { return platform_driver_register(&gpio_ir_recv_driver); } module_init(gpio_ir_recv_driver_init); //…
該平台驅動的.name定義如下所示:
#define GPIO_IR_DRIVER_NAME "gpio-rc-recv"
所以我們后面創建紅外platform_device平台設備時, .name也要寫成"gpio-rc-recv"
2.2 分析gpio-ir-recv.c的probe函數
PS:在probe函數里,主要是獲取平台設備pdev->dev.platform_data內容.該內容在1.2小結講解過了.
代碼如下:
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;
//獲取gpio_ir_recv_platform_data結構體 int rc; //… … if (pdata->gpio_nr < 0) //判斷管腳有效性 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,表示支持所有協議類型 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"); //申請IO管腳 if (rc < 0) goto err_gpio_request; rc = gpio_direction_input(pdata->gpio_nr); //設置為輸入 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); //創建gpio_ir_recv_irq中斷函數,為上下沿觸發 return 0; //… … }
接下來,我們來看看gpio_ir_recv_irq()函數,看看如何實現解碼的
2.3 分析gpio-ir-recv.c的gpio_ir_recv_irq函數
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; //默認定義類型為IR_SPACE (紅外接收的間隔信號) gval = gpio_get_value_cansleep(gpio_dev->gpio_nr); //獲取GPIO的值 if (gval < 0) goto err_get_value; if (gpio_dev->active_low) //低電平有效 gval = !gval; //取反 if (gval == 1) type = IR_PULSE; //收到的是脈沖信號 rc = ir_raw_event_store_edge(gpio_dev->rcdev, type); //通過內核時間,計算出當前波形的持續時間,並保存 if (rc < 0) goto err_get_value; ir_raw_event_handle(gpio_dev->rcdev); //啟動內核解碼對應的線程,來處理波形 err_get_value: return IRQ_HANDLED; }
接下來分析ir_raw_event_handle()函數如何處理波形的.
2.4 gpio_ir_recv_irq ()->ir_raw_event_handle()函數
該函數如下所示:
如上圖所示,最終會喚醒一個線程,該線程對應的函數為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: 存儲內核里注冊的各個解碼協議ir_raw_handler結構體,比如NEC, SANYO, RC5等 handler->decode(raw->dev, ev); //調用解碼函數 … … };
2.5 接下來,我們看看解碼文件是如何添加到ir_raw_handler_list表的
由於我們選擇的是NEC協議(CONFIG_IR_NEC_DECODER=y),所以以/drivers/media/rc/ir-nec-decoder.c為例
1)首先查看ir-nec-decoder.c的init函數:
如上圖所示,可以看到通過ir_raw_handler_register()來注冊.
2) 然后ir_raw_handler_register()里,則將該nec_handler添加到ir_raw_handler_list表:
3.接下來,我們來分析ir_nec_decode()解碼函數如何解碼的.
3.1分析ir_nec_decode()解碼函數
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)) //判斷協議是否支持 return 0; //… … switch (data->state) { case STATE_INACTIVE: if (!ev.pulse) break; if (eq_margin(ev.duration, NEC_HEADER_PULSE, NEC_UNIT * 2)) { //判斷ev.duration 是否等於9ms頭引導碼 data->is_nec_x = false; //標記當前格式不是NECX編碼格式 data->necx_repeat = false; } else if (eq_margin(ev.duration, NECX_HEADER_PULSE, NEC_UNIT / 2)) //另一種不常見的NECX引導碼 data->is_nec_x = true; //標記是NECX編碼格式 else break; data->count = 0; data->state = STATE_HEADER_SPACE; //進入判斷引導碼間隔值,是4.5ms還是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 間隔引導碼 data->state = STATE_BIT_PULSE; //進入解析32bit模式 return 0; } else if (eq_margin(ev.duration, NEC_REPEAT_SPACE, NEC_UNIT / 2)) { //如果ev.duration=2.5ms ,表示重復引導碼 if (!dev->keypressed) { //dev->keypressed是松開的,則放棄(這里有BUG,后面會分析到) IR_dprintk(1, "Discarding last key repeat: event after key up\n"); } else { rc_repeat(dev); //dev->keypressed是未松開,則上報事件 IR_dprintk(1, "Repeat last key\n"); data->state = STATE_TRAILER_PULSE; } return 0; } break; case STATE_BIT_PULSE: //接收數據位的脈沖數據 if (!ev.pulse) break; if (!eq_margin(ev.duration, NEC_BIT_PULSE, NEC_UNIT / 2)) //不等於0.56ms,則忽略掉 break; data->state = STATE_BIT_SPACE; //等於0.56ms,接下來進入STATE_BIT_SPACE,開始解析數據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編碼格式 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 數據1 data->bits |= 1; else if (!eq_margin(ev.duration, NEC_BIT_0_SPACE, NEC_UNIT / 2)) // 既不等於1.68ms,也不等於0.56ms,則是無效數據 break; data->count++; if (data->count == NEC_NBITS) //data->count == 32,則表示數據接收完成 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) { //解析數據 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); //通過scancode編碼來上報按鍵事件 data->state = STATE_INACTIVE; return 0; } //… … }
3.2接下來分析ir_nec_decode ()->rc_keydown()如何通過scancode編碼來上報按鍵事件
void rc_keydown(struct rc_dev *dev, int scancode, u8 toggle) { unsigned long flags; u32 keycode = rc_g_keycode_from_table(dev, scancode); //從鍵映射表里找到編碼對應的鍵值 spin_lock_irqsave(&dev->keylock, flags); if(keycode){ //如果找到鍵值 ir_do_keydown(dev, scancode, keycode, toggle); //上報按鍵事件 if (dev->keypressed) { //如果是按下,則啟動timer_keyup定時器, IR_KEYPRESS_TIMEOUT(20ms)后上報key松開事件 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); }
上個函數里的dev->timer_keyup定時器對應的函數為ir_timer_keyup(),該函數會去調用一次ir_do_keyup()函數,上報key松開事件,該函數如下:
如上圖所示,我們發現dev->keypressed = false,這就是解碼函數出現的BUG:
1)比如當遙控器當按下按鍵時,會上報一次按鍵按下事件,並啟動20ms定時器,用來自動上報按鍵自動按起事件,並標記dev->keypressed = false.
2)然后,如果遙控器一直按下不松手的話,會隔110ms發送一次9ms+2.25ms重復引導碼
3) 然后內核將會調用ir_nec_decode()進行解碼2.25ms
4. 修改ir_nec_decode()函數
接下來,我們修改ir_nec_decode()函數,實現按鍵重復按下,並實現rc_map->repeat_key.
為什么要實現rc_map->repeat_key？
因為rc_map->scan里存儲的鍵值表僅僅表示可支持按下的按鍵, 而rc_map->repeat_key里存儲的才是表示可重復按下的按鍵.
修改之前需要將rc-map.h下的rc_map結構體里添加兩個成員repeat_key和repeat_size(用來實現重復按下功能)
修改后的結構體如下所示:
struct rc_map { struct rc_map_table *scan; unsigned int size; /* Max number of entries */ unsigned int len; /* Used number of entries */ unsigned int alloc; /* Size of *scan in bytes */ enum rc_type rc_type; const char *name; spinlock_t lock; struct rc_map_table *repeat_key; //add unsigned int repeat_size; //add };
然后修改ir_nec_decode(),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; static unsigned char repet_flag=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)) {
repet_flag = 0; data->state = STATE_BIT_PULSE; return 0; } else if (eq_margin(ev.duration, NEC_REPEAT_SPACE, NEC_UNIT / 2)) { //處理重復編碼
if(!repet_flag) //避免第一次按下,出現兩次編碼
{
data->state = STATE_INACTIVE;
repet_flag =1;
}
else
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; //獲取 repeat_size,是否有支持重復按下的按鍵 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); //上報事件 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,表示沒找到有支持重復按鍵,則清空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; }
接下來下章,自己創建一個紅外platform_device平台設備
創建紅外platform_device平台設備步驟為:
- 1) 創建一個platform_device設備,其中.name= "gpio-rc-recv",並注冊設備
- 2) 在drivers\media\rc\keymaps\里創建一個名字為rc-my-text.c鍵值映射文件
下章鏈接: 46.Linux-創建rc紅外遙控平台設備,實現重復功能(2)