一、閃光燈基本原理

工作模式

Camera flash led分flash和torch兩種模式。

• flash：

拍照時上光燈瞬間亮一下，電流比較大，目前是1000mA，最大電流不能超過led最大承受能力

• torch：

只用于錄video或者拿led當手電筒的情況，電流不能太大，

flash開啟需要先從torch過渡，這樣電流可以慢慢增大，減少沖擊。

二、驅動移植

1. 硬件電路

dgm3141總體來說比較簡單，只有兩個引腳用于控制：FLASH_EN、FLASH/TORCH。

• FLASH_EN

閃光燈使能引腳。

• FLASH/TORCH

此處led flash和TORCH功能共用了同一個gpio。

“

注意: 有的攝像頭是通過pwm來控制閃光燈，具體問題具體分析，不要教條

”

2. 設備樹

瑞芯微sdk中沒有專門針對sgm3141的驅動，網(wǎng)上搜了一大圈也沒有搜到，很多閃光燈都是基于I2C接口，通過I2C來設置上光燈的工作模式，好在sdk中有類似的芯片rgb13h驅動，該驅動只有一個引腳用于閃光燈，和我們的功能很類似。

參考驅動文件：leds-rgb13h.c

sgm3141設備樹節(jié)點

       flash_sgm3141:flash-sgm3141 {               status = "okay";               compatible = "sgmicro,sgm3141";               label = "gpio-flash";               pinctrl-names = "default";               pinctrl-0 = <&flash_led_gpios>;                              led-max-microamp = <20000>;               flash-max-microamp = <20000>;               flash-max-timeout-us = <1000000>;               strobe-gpios = <&gpio3 RK_PC7 GPIO_ACTIVE_HIGH>;               enable-gpios = <&gpio3 RK_PD0 GPIO_ACTIVE_HIGH>;               rockchip,camera-module-index = <0>;               rockchip,camera-module-facing = "back";        };        ov13850: ov13850@10 {         ……            flash-leds = <&flash_sgm3141>;         ……        };

pinctrl設置：

 &pinctrl {       ……       flash-led {               flash_led_gpios: flash-led {                       rockchip,pins =                       /* flash led enable*/                       <3 RK_PD0 RK_FUNC_GPIO &pcfg_pull_none>,                       <3 RK_PC6 RK_FUNC_GPIO &pcfg_pull_none>;               };       };       …… };

@drivers/leds/Makefileobj-y                  += sgm3141.o

驅動模塊直接寫死，不羅嗦

三、xml

要app支持閃光燈，還需要修改xml文件，打開該功能

@hardware/rockchip/camera/etc/camera/camera3_profiles.xml@hardware/rockchip/camera/etc/camera/camera3_profiles_rk356x.xml<flash.info.available value="TRUE"/>

這樣，打開app就可以看到上光燈的按鈕。

四、拓撲結構

拓撲結構中entity

rk3568_r:/ # media-ctl -d /dev/media0 -p……- entity 70: m01_f_ov5648 4-0036 (1 pad, 1 link)             type V4L2 subdev subtype Sensor             device node name /dev/v4l-subdev3        pad0: Source                [fmt:SBGGR10/2592x1944]                -> "rockchip-csi2-dphy0":0 []- entity 74: m00_b_ov13850 4-0010 (1 pad, 1 link)             type V4L2 subdev subtype Sensor             device node name /dev/v4l-subdev4        pad0: Source                [fmt:SBGGR10/4224x3136]                -> "rockchip-csi2-dphy0":0 []- entity 78: m00_b_gpio-flash (0 pad, 0 link)             type V4L2 subdev subtype Flash             device node name /dev/v4l-subdev5

• 攝像頭：

m00_b_ov13850、m01_f_ov5648

• 閃光燈：

m00_b_gpio-flash，v4l2子設備/dev/v4l-subdev5

第4個字母b表示后置攝像頭。

五、調試

驅動會通過sysfs創(chuàng)建文件節(jié)點

rk3568_r:/sys/class/leds/gpio-flash # lsbrightness  flash_strobe   max_brightness     power      triggerdevice      flash_timeout  max_flash_timeout  subsystem  uevent

• 亮滅燈

亮燈rk3568_r:/sys/class/leds/gpio-flash # echo 1 > brightnessecho 1 > brightness滅燈1|rk3568_r:/sys/class/leds/gpio-flash # echo 0 > brightnessecho 0 > brightness

操作對應函數(shù)調用關系

[  374.302386] Call trace:                                                                     [  374.302428] dump_backtrace+0x0/0x178                                                        [  374.302471] show_stack+0x14/0x20                                                            [  374.302518] dump_stack+0x94/0xb4                                                            [  374.302560] sgm3141_led_brightness_set+0x18/0x40                                            [  374.302592] led_set_brightness_nopm+0x14/0x48                                               [  374.302624] led_set_brightness+0x50/0x80                                                    [  374.302662] brightness_store+0x74/0xc8                                                      [  374.302691] dev_attr_store+0x18/0x28                                                        [  374.302728] sysfs_kf_write+0x48/0x58                                                        [  374.302759] kernfs_fop_write+0xf4/0x220                                                     [  374.302793] __vfs_write+0x34/0x158                                                          [  374.302810] vfs_write+0xb0/0x1d0                                                            [  374.302828] ksys_write+0x64/0xe0                                                            [  374.302860] __arm64_sys_write+0x14/0x20                                                     [  374.302904] el0_svc_common.constprop.0+0x64/0x178                                           [  374.302947] el0_svc_handler+0x28/0x78                                                       [  374.302984] el0_svc+0x8/0xc                                                                 [  425.607850] healthd: battery l=50 v=3 t=2.6 h=2 st=3 fc=100 chg=au                          [  437.663757] CPU: 3 PID: 1727 Comm: sh Not tainted 4.19.232 #326                             [  437.663869] Hardware name: Rockchip RK3568 EVB1 DDR4 V10 Board (DT)  

• 閃燈

rk3568_r:/sys/class/leds/gpio-flash # echo 1 > flash_strobeecho 1 > flash_strobe

操作對應函數(shù)調用關系

[  492.026239] Call trace:                                                                     [  492.026291] dump_backtrace+0x0/0x178                                                        [  492.026320] show_stack+0x14/0x20                                                            [  492.026354] dump_stack+0x94/0xb4                                                            [  492.026391] sgm3141_led_flash_strobe_set+0x24/0x78                                          [  492.026453] flash_strobe_store+0x88/0xd8                                                    [  492.026517] dev_attr_store+0x18/0x28                                                        [  492.026571] sysfs_kf_write+0x48/0x58                                                        [  492.026620] kernfs_fop_write+0xf4/0x220                                                     [  492.026683] __vfs_write+0x34/0x158                                                          [  492.026733] vfs_write+0xb0/0x1d0                                                            [  492.026784] ksys_write+0x64/0xe0                                                            [  492.026833] __arm64_sys_write+0x14/0x20                                                     [  492.026867] el0_svc_common.constprop.0+0x64/0x178                                           [  492.026912] el0_svc_handler+0x28/0x78                                                       [  492.026966] el0_svc+0x8/0xc                                                                 [  494.218112] CPU: 2 PID: 1727 Comm: sh Not tainted 4.19.232 #326                             [  494.218218] Hardware name: Rockchip RK3568 EVB1 DDR4 V10 Board (DT)  

“

為方便查看驅動回調函數(shù)調用順序，可以在下面3個回調函數(shù)入口增加dump_stack()， sgm3141_led_brightness_set() sgm3141_led_flash_strobe_set() sgm3141_set_ctrl()

”

六、app 測試驅動 log分析

1. 上電加載驅動log

rk3568_r:/ # dmesg | grep sgm3141dmesg | grep sgm3141[    0.853883] sgm3141-flash flash-sgm3141: driver version: 00.01.01[    0.853956] sgm3141-flash flash-sgm3141: Unable to get pwm device

2. 打開攝像頭

打開攝像頭功能，app調用ioctl命令如下：

1. V4L2_CID_FLASH_LED_MODE   ：app 設置led mode為 V4L2_FLASH_LED_MODE_FLASH(1)
2. V4L2_CID_FLASH_TIMEOUT ：設置超時時間
3. V4L2_CID_FLASH_STROBE_STOP ：停止閃光

[   36.213220] sgm3141 V4L2_CID_FLASH_LED_MODE 1[   36.213250] sgm3141_set_ctrl(),376[   36.213256] sgm3141_set_output(),78 0[   36.213265] sgm3141_led_flash_strobe_set(),166 state=1[   36.213281] sgm3141_set_output(),78 1[   36.213298] sgm3141 V4L2_CID_FLASH_TIMEOUT[   36.213300] sgm3141_set_ctrl(),412[   36.213308] sgm3141_led_flash_timeout_set(),195 timeout=500000[   36.213318] sgm3141 V4L2_CID_FLASH_STROBE_STOP 1[   36.213323] sgm3141_set_ctrl(),406[   36.213327] sgm3141_led_flash_strobe_set(),166 state=0[   36.213332] sgm3141_set_output(),78 0[   36.213461] sgm3141_timeout_work(),117

3. 拍照

拍照功能，app調用ioctl命令如下：

1. V4L2_CID_FLASH_LED_MODE ：設置led mod為 V4L2_FLASH_LED_MODE_TORCH(2),并點燈
2. V4L2_CID_FLASH_LED_MODE：到達指定超時時間（2.7秒），設置led mod為 V4L2_FLASH_LED_MODE_NONE 0
3. V4L2_CID_FLASH_LED_MODE：在此設置led mod為V4L2_FLASH_LED_MODE_FLASH(1)
4. V4L2_CID_FLASH_STROBE_STOP:停止閃光

[   90.246203] sgm3141 V4L2_CID_FLASH_LED_MODE 2[   90.246251] sgm3141_set_ctrl(),376[   90.246262] sgm3141_set_output(),78 0[   90.246277] sgm3141_set_output(),78 1[   92.902746] sgm3141 V4L2_CID_FLASH_LED_MODE 0[   92.902775] sgm3141_set_ctrl(),376[   92.902781] sgm3141_set_output(),78 0[   93.034903] sgm3141 V4L2_CID_FLASH_LED_MODE 1[   93.034929] sgm3141_set_ctrl(),376[   93.034934] sgm3141_set_output(),78 0[   93.034943] sgm3141_led_flash_strobe_set(),166 state=1[   93.034959] sgm3141_set_output(),78 1[   93.034977] sgm3141 V4L2_CID_FLASH_STROBE_STOP 1[   93.034988] sgm3141_set_ctrl(),406[   93.034993] sgm3141_led_flash_strobe_set(),166 state=0[   93.035002] sgm3141_set_output(),78 0[   93.035058] sgm3141_timeout_work(),117

從log可以看出，app拍照的時候，閃光燈操作是通過v4l2下發(fā)的命令，

而我們直接操作宏dev_attr_store創(chuàng)建的文件節(jié)點則是通過在sysfs文件節(jié)點（brightness  flash_strobe）直接調用到操作函數(shù)。

4. 退出攝像頭

[  317.882459] sgm3141 V4L2_CID_FLASH_LED_MODE 0[  317.882522] sgm3141_set_ctrl(),376[  317.882532] sgm3141_set_output(),78 0

七、驅動獲取

一口君修改過的驅動已經(jīng)上傳到gitee，獲取地址：https://gitee.com/yikoulinux/sgm3141