[PATCH v5 12/17] media: i2c: cap exposure at height + vblank in ov8865

[Daniel Scally <djrscally@xxxxxxxxx>]

Exposure limits depend on the total height; when vblank is altered (and
thus the total height is altered), change the exposure limits to reflect
the new cap.

Signed-off-by: Daniel Scally <djrscally@xxxxxxxxx>
---
Changes in v5: 

	- (JM) Added OV8865_INTEGRATION_TIME_MARGIN to reduce the maximum
	possible exposure, without which setting values within 8 lines of max
	causes an entirely black image.

 drivers/media/i2c/ov8865.c | 28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/drivers/media/i2c/ov8865.c b/drivers/media/i2c/ov8865.c
index f4a899e463de..811438c44b58 100644
--- a/drivers/media/i2c/ov8865.c
+++ b/drivers/media/i2c/ov8865.c
@@ -143,6 +143,7 @@
 #define OV8865_EXPOSURE_CTRL_L_REG		0x3502
 #define OV8865_EXPOSURE_CTRL_L(v)		((v) & GENMASK(7, 0))
 #define OV8865_EXPOSURE_GAIN_MANUAL_REG		0x3503
+#define OV8865_INTEGRATION_TIME_MARGIN		8
 
 #define OV8865_GAIN_CTRL_H_REG			0x3508
 #define OV8865_GAIN_CTRL_H(v)			(((v) & GENMASK(12, 8)) >> 8)
@@ -677,6 +678,7 @@ struct ov8865_ctrls {
 	struct v4l2_ctrl *pixel_rate;
 	struct v4l2_ctrl *hblank;
 	struct v4l2_ctrl *vblank;
+	struct v4l2_ctrl *exposure;
 
 	struct v4l2_ctrl_handler handler;
 };
@@ -2454,6 +2456,20 @@ static int ov8865_s_ctrl(struct v4l2_ctrl *ctrl)
 	unsigned int index;
 	int ret;
 
+	/* If VBLANK is altered we need to update exposure to compensate */
+	if (ctrl->id == V4L2_CID_VBLANK) {
+		int exposure_max;
+
+		exposure_max = sensor->state.mode->output_size_y + ctrl->val -
+			       OV8865_INTEGRATION_TIME_MARGIN;
+		__v4l2_ctrl_modify_range(sensor->ctrls.exposure,
+					 sensor->ctrls.exposure->minimum,
+					 exposure_max,
+					 sensor->ctrls.exposure->step,
+					 min(sensor->ctrls.exposure->val,
+					     exposure_max));
+	}
+
 	/* Wait for the sensor to be on before setting controls. */
 	if (pm_runtime_suspended(sensor->dev))
 		return 0;
@@ -2510,8 +2526,8 @@ static int ov8865_ctrls_init(struct ov8865_sensor *sensor)
 
 	/* Exposure */
 
-	v4l2_ctrl_new_std(handler, ops, V4L2_CID_EXPOSURE, 16, 1048575, 16,
-			  512);
+	ctrls->exposure = v4l2_ctrl_new_std(handler, ops, V4L2_CID_EXPOSURE, 16,
+					    1048575, 16, 512);
 
 	/* Gain */
 
@@ -2700,6 +2716,7 @@ static int ov8865_set_fmt(struct v4l2_subdev *subdev,
 	u32 mbus_code = 0;
 	unsigned int hblank;
 	unsigned int index;
+	int exposure_max;
 	int ret = 0;
 
 	mutex_lock(&sensor->mutex);
@@ -2747,6 +2764,13 @@ static int ov8865_set_fmt(struct v4l2_subdev *subdev,
 	__v4l2_ctrl_modify_range(sensor->ctrls.hblank, hblank, hblank, 1,
 				 hblank);
 
+	exposure_max = mode->vts - OV8865_INTEGRATION_TIME_MARGIN;
+	__v4l2_ctrl_modify_range(sensor->ctrls.exposure,
+				 sensor->ctrls.exposure->minimum, exposure_max,
+				 sensor->ctrls.exposure->step,
+				 min(sensor->ctrls.exposure->val,
+				     exposure_max));
+
 complete:
 	mutex_unlock(&sensor->mutex);
 
-- 
2.25.1