media: i2c: imx290: Add exposure time control

Support configuring the exposure time, which is expressed as the
complement of the exposure time (frame period minus integration time).
The frame period is currently fixed.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>

drivers/media/i2c/imx290.c

@@ -103,6 +103,8 @@
 #define IMX290_PGCTRL_THRU				BIT(1)
 #define IMX290_PGCTRL_MODE(n)				((n) << 4)
 
+#define IMX290_VMAX_DEFAULT				1125
+
 static const char * const imx290_supply_name[] = {
 	"vdda",
 	"vddd",
@@ -176,7 +178,7 @@ static const char * const imx290_test_pattern_menu[] = {
 
 static const struct imx290_regval imx290_global_init_settings[] = {
 	{ IMX290_CTRL_07, IMX290_WINMODE_1080P },
-	{ IMX290_VMAX, 1125 },
+	{ IMX290_VMAX, IMX290_VMAX_DEFAULT },
 	{ IMX290_EXTCK_FREQ, 0x2520 },
 	{ IMX290_WINWV_OB, 12 },
 	{ IMX290_WINPH, 0 },
@@ -480,6 +482,12 @@ static int imx290_set_ctrl(struct v4l2_ctrl *ctrl)
 	case V4L2_CID_GAIN:
 		ret = imx290_write(imx290, IMX290_GAIN, ctrl->val, NULL);
 		break;
+
+	case V4L2_CID_EXPOSURE:
+		ret = imx290_write(imx290, IMX290_SHS1,
+				   IMX290_VMAX_DEFAULT - ctrl->val - 1, NULL);
+		break;
+
 	case V4L2_CID_TEST_PATTERN:
 		if (ctrl->val) {
 			imx290_write(imx290, IMX290_BLKLEVEL, 0, &ret);
@@ -1008,12 +1016,16 @@ static int imx290_probe(struct i2c_client *client)
 	 */
 	imx290_entity_init_cfg(&imx290->sd, NULL);
 
-	v4l2_ctrl_handler_init(&imx290->ctrls, 4);
+	v4l2_ctrl_handler_init(&imx290->ctrls, 5);
 	imx290->ctrls.lock = &imx290->lock;
 
 	v4l2_ctrl_new_std(&imx290->ctrls, &imx290_ctrl_ops,
 			  V4L2_CID_GAIN, 0, 72, 1, 0);
 
+	v4l2_ctrl_new_std(&imx290->ctrls, &imx290_ctrl_ops,
+			  V4L2_CID_EXPOSURE, 1, IMX290_VMAX_DEFAULT - 2, 1,
+			  IMX290_VMAX_DEFAULT - 2);
+
 	imx290->link_freq =
 		v4l2_ctrl_new_int_menu(&imx290->ctrls, &imx290_ctrl_ops,
 				       V4L2_CID_LINK_FREQ,