v4l2: add automatic power line frequency detection

modules/access/v4l2/v4l2.h

@@ -32,6 +32,7 @@
 #ifndef V4L2_CTRL_FLAG_VOLATILE /* 3.2 */
 # warning Please update Video4Linux2 headers!
 # define V4L2_CTRL_FLAG_VOLATILE 0x0080
+# define V4L2_CID_POWER_LINE_FREQUENCY_AUTO 3
 # define V4L2_STD_G (V4L2_STD_PAL_G|V4L2_STD_SECAM_G)
 # define V4L2_STD_H (V4L2_STD_PAL_H|V4L2_STD_SECAM_H)
 # define V4L2_STD_L (V4L2_STD_SECAM_L|V4L2_STD_SECAM_LC)

modules/access/v4l2/video.c

@@ -140,9 +140,10 @@ static const int power_freq_vlc[] = { -1,
     V4L2_CID_POWER_LINE_FREQUENCY_DISABLED,
     V4L2_CID_POWER_LINE_FREQUENCY_50HZ,
     V4L2_CID_POWER_LINE_FREQUENCY_60HZ,
+    V4L2_CID_POWER_LINE_FREQUENCY_AUTO,
 };
 static const char *const power_freq_user[] = { N_("Unspecified"),
-    N_("Off"), N_("50 Hz"), N_("60 Hz"),
+    N_("Off"), N_("50 Hz"), N_("60 Hz"), N_("Automatic"),
 };
 #define BKLT_COMPENSATE_TEXT N_( "Backlight compensation" )
 #define BKLT_COMPENSATE_LONGTEXT N_( "Backlight compensation." )