v4l2: Add a Greyworld AWB mode.

raspberrypi inclusion
category: feature
bugzilla: 50432

--------------------------------

Adds a simple greyworld white balance preset, mainly for use
with cameras without an IR filter (eg Raspberry Pi NoIR)
Signed-off-by: NDave Stevenson <dave.stevenson@raspberrypi.org>
Signed-off-by: NFang Yafen <yafen@iscas.ac.cn>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

drivers/media/v4l2-core/v4l2-ctrls.c

@@ -275,6 +275,7 @@ const char * const *v4l2_ctrl_get_menu(u32 id)
 		"Flash",
 		"Cloudy",
 		"Shade",
+		"Greyworld",
 		NULL,
 	};
 	static const char * const camera_iso_sensitivity_auto[] = {

include/uapi/linux/v4l2-controls.h

@@ -886,6 +886,7 @@ enum v4l2_auto_n_preset_white_balance {
 	V4L2_WHITE_BALANCE_FLASH		= 7,
 	V4L2_WHITE_BALANCE_CLOUDY		= 8,
 	V4L2_WHITE_BALANCE_SHADE		= 9,
+	V4L2_WHITE_BALANCE_GREYWORLD		= 10,
 };
 
 #define V4L2_CID_WIDE_DYNAMIC_RANGE		(V4L2_CID_CAMERA_CLASS_BASE+21)