Android S5PV210 camera S_INPUT实现

三星平台的capture设备节点是/dev/fimc0，但是平台可能存在多个摄像头，更特殊的情况是一个video ADC芯片外接多个模拟摄像头，这几天研究了下如何选择capture的摄像头，做个总结。

先对摄像头做个分类，1. CMM CameraCompact Module 摄像头模组； 2. VIDEO ADC + 模拟摄像头

视频源的选择是通过VIDIOC_S_INPUT来实现的，这里的视频源既可以是上面第一类的CMM，也可以是第二类的ADC加一个模拟摄像头，video ADC挂几个模拟摄像头就对应几个视频源。

三星FIMC框架为每一个视频源定义了一个结构，以mach-smdkc110.c为例。

1901 static struct s3c_platform_fimc fimc_plat_lsi = {1902     .srclk_name = "mout_mpll",1903     .clk_name   = "sclk_fimc",1904     .lclk_name  = "sclk_fimc_lclk",1905     .clk_rate   = 166750000,1906 #if defined(CONFIG_VIDEO_S5K4EA)1907     .default_cam    = CAMERA_CSI_C,1908 #else1909 #ifdef CAM_ITU_CH_A1910     .default_cam    = CAMERA_PAR_A,1911 #else1912     .default_cam    = CAMERA_PAR_B,1913 #endif1914 #endif1915     .camera     = {1916 #ifdef CONFIG_VIDEO_S5K4ECGX1917             &s5k4ecgx,1918 #endif1919 #ifdef CONFIG_VIDEO_S5KA3DFX1920             &s5ka3dfx,1921 #endif1922 #ifdef CONFIG_VIDEO_S5K4BA1923             &s5k4ba,1924 #endif1925 #ifdef CONFIG_VIDEO_S5K4EA1926             &s5k4ea,1927 #endif1928 #ifdef CONFIG_VIDEO_CAM80001929             &cam8000,1930 #endif1931 #ifdef CONFIG_VIDEO_TW99121932             &tw9912_1,1933             &tw9912_2,1934 #endif1935     },1936     .hw_ver     = 0x43,1937 };

1918 ～ 1938 .camera成员定义了系统可能的视频源，其中s5k4ecgx, s5ka3dfx, s5k4ba, s5k4ea是四个CMM模组， cam8000原生代码的Video ADC，tw9912_1和tw9912_2是我定义的两个camera 视频源，为什么一个TW9912 Video ADC要定义成两个，这是因为在我的项目中TW9912存在两路输入，一个是CVBS另外一个是YPbPr，我认为他们和 TW9912组成了两个camera 视频源。

下面代码演示了如何区分这两个camera通道

1831 static struct s3c_platform_camera tw9912_1 = {1832     .id     = CAMERA_PAR_A,1833     .type       = CAM_TYPE_ITU,1834     .fmt        = ITU_656_YCBCR422_8BIT,1835     .order422   = CAM_ORDER422_8BIT_CBYCRY,1836     .i2c_busnum = 1,1837     .info       = &tw9912_1_i2c_info,1838     .pixelformat = V4L2_PIX_FMT_YUYV,1839     .srclk_name = "mout_mpll",1840     .clk_name   = "sclk_cam0",1841     .clk_rate   = 44000000,1842     .line_length = 1440,1843     .width      = 720,1844     .height     = 576,1845     .window     = {1846         .left   = 0,1847         .top    = 0,1848         .width  = 720,1849         .height = 576,1850     },18511852     /* Polarity */1853     .inv_pclk   = 0,1854     .inv_vsync  = 0,1855     .inv_href   = 0,1856     .inv_hsync  = 0,18571858     .initialized    = 0,1859     /*1860      * It is too late to call camera sensor poweron in fimc_camera_init1861      * so we move power function to board init1862      */1863     .cam_power  = NULL,1864 };1866 static struct s3c_platform_camera tw9912_2 = {1867     .id     = CAMERA_PAR_A,1868     .type       = CAM_TYPE_ITU,1869     .fmt        = ITU_656_YCBCR422_8BIT,1870     .order422   = CAM_ORDER422_8BIT_CBYCRY,1871     .i2c_busnum = 1,1872     .info       = &tw9912_2_i2c_info,1873     .pixelformat = V4L2_PIX_FMT_YUYV,1874     .srclk_name = "mout_mpll",1875     .clk_name   = "sclk_cam0",1876     .clk_rate   = 44000000,1877     .line_length = 1440,1878     .width      = 720,1879     .height     = 576,1880     .window     = {1881         .left   = 0,1882         .top    = 0,1883         .width  = 720,1884         .height = 576,1885     },18861887     /* Polarity */1888     .inv_pclk   = 0,1889     .inv_vsync  = 0,1890     .inv_href   = 0,1891     .inv_hsync  = 0,18921893     .initialized    = 0,1894     /*1895      * It is too late to call camera sensor poweron in fimc_camera_init1896      * so we move power function to board init1897      */1898     .cam_power  = NULL,1899 };

他们唯一不同的地方在于.info成员，分别为tw9912_1_i2c_info 和tw9912_2_i2c_info

1796 static struct tw9912_platform_data tw9912_1_plat = {1797     .default_width = 720,1798     .default_height = 576,1799     .pixelformat = V4L2_PIX_FMT_YUYV,1800     .ifsel = 0,1801     .ysel = 0,1802     .csel = 0,1803     .vsel = 0,1804     .cam_reset = tw9912_reset,1805 };18061807 static struct tw9912_platform_data tw9912_2_plat = {1808     .default_width = 720,1809     .default_height = 576,1810     .pixelformat = V4L2_PIX_FMT_YUYV,1811     .ifsel = 0x20,1812     .ysel = 0x08,1813     .csel = 0x2,1814     .vsel = 0,1815     .cam_reset = tw9912_reset,1816 };  18171818 static struct i2c_board_info  tw9912_1_i2c_info = {1819     I2C_BOARD_INFO("tw9912", (0x88 >> 1)),1820     .platform_data = &tw9912_1_plat,1821 };  18221823 static struct i2c_board_info  tw9912_2_i2c_info = {1824     I2C_BOARD_INFO("tw9912", (0x88 >> 1)),1825     .platform_data = &tw9912_2_plat,1826 };  

i2c_board_info不同的地方是ifsel, ysel, csel, vsel成员，这几个成员对应着tw9912 0x02寄存器（input format）寄存器位

这是tw9912_1和tw9912_2唯一有差别的地方。

当上层调用VIDIOC_S_INPUT时，调用路径如下

fimc_s_input->fimc_configure_subdev->v4l2_i2c_new_subdev_board->v4l2_subdev_call(sd, core, s_config, info->irq, info->platform_data)->

v4l2_subdev_call(sd, core, s_config, info->irq, info->platform_data)调用sd->ops->core->s_config， 这个函数需要在tw9912驱动中实现，info->platform_data就是在mach-smkvc110.c中定义的tw9912_1_i2c_info或者tw9912_2_i2c_info，因此在s_config实现中就可以根据i2c_board_info.platform_data中的ifsel, ysel, csel, vsel来设置tw9912的输入

总结一下：

1. video ADC芯片驱动要通过s_config来实现视频源的切换

2. 为video ADC的每个输入创建一个s3c_platform_camera 结构，通过i2c_board_info.platform_data来体现输入的差异性