media: imx355: Define the exposure offset, and use that define

The difference between frame length and max exposure time in
lines is 10. That had been used as a bare value in calculations.

Move it to a define, and use that define.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>

Author: 6by9

drivers/media/i2c/imx355.c

@@ -55,6 +55,7 @@
 #define IMX355_EXPOSURE_MIN		1
 #define IMX355_EXPOSURE_STEP		1
 #define IMX355_EXPOSURE_DEFAULT		0x0282
+#define IMX355_EXPOSURE_OFFSET		10
 
 /* Analog gain control */
 #define IMX355_REG_ANALOG_GAIN		CCI_REG16(0x0204)
@@ -615,7 +616,7 @@ static int imx355_set_ctrl(struct v4l2_ctrl *ctrl)
 	switch (ctrl->id) {
 	case V4L2_CID_VBLANK:
 		/* Update max exposure while meeting expected vblanking */
-		max = format->height + ctrl->val - 10;
+		max = format->height + ctrl->val - IMX355_EXPOSURE_OFFSET;
 		__v4l2_ctrl_modify_range(imx355->exposure,
 					 imx355->exposure->minimum,
 					 max, imx355->exposure->step, max);
@@ -1077,7 +1078,7 @@ static int imx355_init_controls(struct imx355 *imx355)
 		imx355->hblank->flags |= V4L2_CTRL_FLAG_READ_ONLY;
 
 	/* fll >= exposure time + adjust parameter (default value is 10) */
-	exposure_max = mode->fll_def - 10;
+	exposure_max = mode->fll_def - IMX355_EXPOSURE_OFFSET;
 	imx355->exposure = v4l2_ctrl_new_std(ctrl_hdlr, &imx355_ctrl_ops,
 					     V4L2_CID_EXPOSURE,
 					     IMX355_EXPOSURE_MIN, exposure_max,