linux-kernel - Re: [PATCH v7 10/10] media: i2c: ov9282: dynamic flash

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Message-ID: <aLYNQ4W8f55G_7HP@kekkonen.localdomain>
Date: Tue, 2 Sep 2025 00:16:51 +0300
From: Sakari Ailus <sakari.ailus@...ux.intel.com>
To: Richard Leitner <richard.leitner@...ux.dev>
Cc: 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>,
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-leds@...r.kernel.org, Hans Verkuil <hverkuil@...nel.org>
Subject: Re: [PATCH v7 10/10] media: i2c: ov9282: dynamic flash_duration
 maximum

Hi Richard,

On Mon, Sep 01, 2025 at 05:05:15PM +0200, Richard Leitner wrote:
> 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 b104ae77f00e9e7777342e48b7bf3caa6d297f69..3253d9f271cb3caef6d85837ebec4f5beb466a4d 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;

Redundant parentheses.

> +
> +	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 us), 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;
>  
> @@ -1491,8 +1510,11 @@ static int ov9282_init_controls(struct ov9282 *ov9282)
>  	/* Flash/Strobe controls */
>  	v4l2_ctrl_new_std(ctrl_hdlr, &ov9282_ctrl_ops, V4L2_CID_FLASH_HW_STROBE_SIGNAL, 0, 1, 1, 0);
>  
> -	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);

Wrap this differently, please, e.g. after '='.

>  
>  	ctrl = v4l2_ctrl_new_std_menu(ctrl_hdlr, &ov9282_ctrl_ops,
>  				      V4L2_CID_FLASH_STROBE_SOURCE,
> 

To me the set looks good but I wouldn't mind about having a bit more
review.

-- 
Kind regards,

Sakari Ailus