linux-kernel - [PATCH v5 10/10] media: i2c: ov9282: dynamic flash

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Message-Id: <20250617-ov9282-flash-strobe-v5-10-9762da74d065@linux.dev>
Date: Tue, 17 Jun 2025 09:31:44 +0200
From: Richard Leitner <richard.leitner@...ux.dev>
To: Sakari Ailus <sakari.ailus@...ux.intel.com>, 
 Dave Stevenson <dave.stevenson@...pberrypi.com>, 
 Mauro Carvalho Chehab <mchehab@...nel.org>, Lee Jones <lee@...nel.org>, 
 Pavel Machek <pavel@...nel.org>, 
 Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: Hans Verkuil <hverkuil@...all.nl>, linux-media@...r.kernel.org, 
 linux-kernel@...r.kernel.org, linux-leds@...r.kernel.org, 
 Richard Leitner <richard.leitner@...ux.dev>
Subject: [PATCH v5 10/10] media: i2c: ov9282: dynamic flash_duration
 maximum

This patch sets the current exposure time as maximum for the
flash_duration control. As Flash/Strobes which are longer than the
exposure time have no effect.

Signed-off-by: Richard Leitner <richard.leitner@...ux.dev>
---
 drivers/media/i2c/ov9282.c | 30 ++++++++++++++++++++++++++----
 1 file changed, 26 insertions(+), 4 deletions(-)

diff --git a/drivers/media/i2c/ov9282.c b/drivers/media/i2c/ov9282.c
index 1f4bca29cd793e99c473aff9c8b7e200e3d598bc..2fd0d63b8071d434c05a98f4d0169c4fb83f7cfe 100644
--- a/drivers/media/i2c/ov9282.c
+++ b/drivers/media/i2c/ov9282.c
@@ -198,6 +198,7 @@ struct ov9282_mode {
  * @exp_ctrl: Pointer to exposure control
  * @again_ctrl: Pointer to analog gain control
  * @pixel_rate: Pointer to pixel rate control
+ * @flash_duration: Pointer to flash duration control
  * @vblank: Vertical blanking in lines
  * @noncontinuous_clock: Selection of CSI2 noncontinuous clock mode
  * @cur_mode: Pointer to current selected sensor mode
@@ -220,6 +221,7 @@ struct ov9282 {
 		struct v4l2_ctrl *again_ctrl;
 	};
 	struct v4l2_ctrl *pixel_rate;
+	struct v4l2_ctrl *flash_duration;
 	u32 vblank;
 	bool noncontinuous_clock;
 	const struct ov9282_mode *cur_mode;
@@ -611,6 +613,15 @@ static int ov9282_update_controls(struct ov9282 *ov9282,
 					mode->vblank_max, 1, mode->vblank);
 }
 
+static u32 ov9282_exposure_to_us(struct ov9282 *ov9282, u32 exposure)
+{
+	/* calculate exposure time in µs */
+	u32 frame_width = ov9282->cur_mode->width + ov9282->hblank_ctrl->val;
+	u32 trow_us = (frame_width * 1000000UL) / ov9282->pixel_rate->val;
+
+	return exposure * trow_us;
+}
+
 /**
  * ov9282_update_exp_gain() - Set updated exposure and gain
  * @ov9282: pointer to ov9282 device
@@ -622,9 +633,10 @@ static int ov9282_update_controls(struct ov9282 *ov9282,
 static int ov9282_update_exp_gain(struct ov9282 *ov9282, u32 exposure, u32 gain)
 {
 	int ret;
+	u32 exposure_us = ov9282_exposure_to_us(ov9282, exposure);
 
-	dev_dbg(ov9282->dev, "Set exp %u, analog gain %u",
-		exposure, gain);
+	dev_dbg(ov9282->dev, "Set exp %u (~%u µs), analog gain %u",
+		exposure, exposure_us, gain);
 
 	ret = ov9282_write_reg(ov9282, OV9282_REG_HOLD, 1, 1);
 	if (ret)
@@ -635,6 +647,12 @@ static int ov9282_update_exp_gain(struct ov9282 *ov9282, u32 exposure, u32 gain)
 		goto error_release_group_hold;
 
 	ret = ov9282_write_reg(ov9282, OV9282_REG_AGAIN, 1, gain);
+	if (ret)
+		goto error_release_group_hold;
+
+	ret = __v4l2_ctrl_modify_range(ov9282->flash_duration,
+				       0, exposure_us, 1,
+				       OV9282_FLASH_DURATION_DEFAULT);
 
 error_release_group_hold:
 	ov9282_write_reg(ov9282, OV9282_REG_HOLD, 1, 0);
@@ -1420,6 +1438,7 @@ static int ov9282_init_controls(struct ov9282 *ov9282)
 	struct v4l2_fwnode_device_properties props;
 	struct v4l2_ctrl *ctrl;
 	u32 hblank_min;
+	u32 exposure_us;
 	u32 lpfr;
 	int ret;
 
@@ -1495,8 +1514,11 @@ static int ov9282_init_controls(struct ov9282 *ov9282)
 			       (1 << V4L2_FLASH_LED_MODE_TORCH),
 			       V4L2_FLASH_LED_MODE_NONE);
 
-	v4l2_ctrl_new_std(ctrl_hdlr, &ov9282_ctrl_ops, V4L2_CID_FLASH_DURATION,
-			  0, 13900, 1, 8);
+	exposure_us = ov9282_exposure_to_us(ov9282, OV9282_EXPOSURE_DEFAULT);
+	ov9282->flash_duration = v4l2_ctrl_new_std(ctrl_hdlr,
+						   &ov9282_ctrl_ops, V4L2_CID_FLASH_DURATION,
+						   0, exposure_us,
+						   1, OV9282_FLASH_DURATION_DEFAULT);
 
 	ctrl = v4l2_ctrl_new_std_menu(ctrl_hdlr, &ov9282_ctrl_ops,
 				      V4L2_CID_FLASH_STROBE_SOURCE,

-- 
2.47.2