linux-kernel - Re: [PATCH v7 02/10] media: v4l2-flash: add support for flash/strobe duration

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Message-ID: <2u6jncxsvlzbs5d6uhxslxnyvtidagspb3rfxsnhm3beb5saa5@ctq2cftpcwry>
Date: Mon, 8 Sep 2025 16:15:48 +0200
From: Richard Leitner <richard.leitner@...ux.dev>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>, 
	Lee Jones <lee@...nel.org>
Cc: Sakari Ailus <sakari.ailus@...ux.intel.com>, 
	Dave Stevenson <dave.stevenson@...pberrypi.com>, Mauro Carvalho Chehab <mchehab@...nel.org>, 
	Pavel Machek <pavel@...nel.org>, linux-media@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-leds@...r.kernel.org, Hans Verkuil <hverkuil@...nel.org>
Subject: Re: [PATCH v7 02/10] media: v4l2-flash: add support for flash/strobe
 duration

Hi Laurent,

On Sun, Sep 07, 2025 at 09:05:20PM +0200, Laurent Pinchart wrote:
> Hi Richard,
> 
> Thank you for the patch.
> 
> On Mon, Sep 01, 2025 at 05:05:07PM +0200, Richard Leitner wrote:
> > Add support for the new V4L2_CID_FLASH_DURATION control to the v4l2
> > flash led class.
> 
> I don't think this is a good idea, based on the reasoning explained in
> the review of 01/10. If V4L2_CID_FLASH_DURATION is meant to indicate the
> duration of the external flash/strobe pulse signal, it should be
> implemented by the source of the signal, and for external strobe mode
> only. The flash controller, which receives the flash/strobe pulse,
> should implement the timeout control.

You're right. From that point of view it makes no sense to have this
functions in v4l2-flash-led-class.c. I'll move the implementation to
ov9282 for v9.

If I do so I guess the patch already merged by Lee needs reverting?
6a09ae828198 (leds: flash: Add support for flash/strobe duration, 2025-05-07)
Should the revert be included in this series then?

> 
> > Signed-off-by: Richard Leitner <richard.leitner@...ux.dev>
> > ---
> >  drivers/media/v4l2-core/v4l2-flash-led-class.c | 25 +++++++++++++++++++++++++
> >  1 file changed, 25 insertions(+)
> > 
> > diff --git a/drivers/media/v4l2-core/v4l2-flash-led-class.c b/drivers/media/v4l2-core/v4l2-flash-led-class.c
> > index 355595a0fefac72c2f6941a30fa430d37dbdccfe..875d56d7190592c1e5ab7acd617b76dcec8792da 100644
> > --- a/drivers/media/v4l2-core/v4l2-flash-led-class.c
> > +++ b/drivers/media/v4l2-core/v4l2-flash-led-class.c
> > @@ -29,6 +29,7 @@ enum ctrl_init_data_id {
> >  	INDICATOR_INTENSITY,
> >  	FLASH_TIMEOUT,
> >  	STROBE_SOURCE,
> > +	FLASH_DURATION,
> >  	/*
> >  	 * Only above values are applicable to
> >  	 * the 'ctrls' array in the struct v4l2_flash.
> > @@ -298,6 +299,12 @@ static int v4l2_flash_s_ctrl(struct v4l2_ctrl *c)
> >  		 * microamperes for flash intensity units.
> >  		 */
> >  		return led_set_flash_brightness(fled_cdev, c->val);
> > +	case V4L2_CID_FLASH_DURATION:
> > +		/*
> > +		 * No conversion is needed as LED Flash class also uses
> > +		 * microseconds for flash duration units.
> > +		 */
> > +		return led_set_flash_duration(fled_cdev, c->val);
> >  	}
> >  
> >  	return -EINVAL;
> > @@ -424,6 +431,14 @@ static void __fill_ctrl_init_data(struct v4l2_flash *v4l2_flash,
> >  		ctrl_cfg->flags = V4L2_CTRL_FLAG_VOLATILE |
> >  				  V4L2_CTRL_FLAG_EXECUTE_ON_WRITE;
> >  	}
> > +
> > +	/* Init FLASH_DURATION ctrl data */
> > +	if (has_flash_op(fled_cdev, duration_set)) {
> > +		ctrl_init_data[FLASH_DURATION].cid = V4L2_CID_FLASH_DURATION;
> > +		ctrl_cfg = &ctrl_init_data[FLASH_DURATION].config;
> > +		__lfs_to_v4l2_ctrl_config(&fled_cdev->duration, ctrl_cfg);
> > +		ctrl_cfg->id = V4L2_CID_FLASH_DURATION;
> > +	}
> >  }
> >  
> >  static int v4l2_flash_init_controls(struct v4l2_flash *v4l2_flash,
> > @@ -543,6 +558,16 @@ static int __sync_device_with_v4l2_controls(struct v4l2_flash *v4l2_flash)
> >  			return ret;
> >  	}
> >  
> > +	if (ctrls[FLASH_DURATION]) {
> > +		if (WARN_ON_ONCE(!fled_cdev))
> > +			return -EINVAL;
> > +
> > +		ret = led_set_flash_duration(fled_cdev,
> > +					     ctrls[FLASH_DURATION]->val);
> > +		if (ret < 0)
> > +			return ret;
> > +	}
> > +
> >  	/*
> >  	 * For some hardware arrangements setting strobe source may affect
> >  	 * torch mode. Synchronize strobe source setting only if not in torch
> 
> -- 
> Regards,
> 
> Laurent Pinchart

thanks again for your review!

regards;rl