linux-kernel - Re: [PATCH v2 4/8] Documentation: uAPI: media: add V4L2_CID_FLASH

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Message-ID: <4w7s6g32rol2ptkchczhyhgvytyeq6baqvz4h7ikurzg2tygnr@a3q7cgeagzk4>
Date: Fri, 14 Mar 2025 11:28:33 +0100
From: Richard Leitner <richard.leitner@...ux.dev>
To: Hans Verkuil <hverkuil@...all.nl>
Cc: 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>, linux-media@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-leds@...r.kernel.org
Subject: Re: [PATCH v2 4/8] Documentation: uAPI: media: add
 V4L2_CID_FLASH_DURATION

Hi Hans,

thanks for your quick feedback!

On Fri, Mar 14, 2025 at 10:41:04AM +0100, Hans Verkuil wrote:
> On 14/03/2025 09:49, Richard Leitner wrote:
> > Add the new strobe_duration control to v4l uAPI documentation.
> > 
> > Signed-off-by: Richard Leitner <richard.leitner@...ux.dev>
> > ---
> >  Documentation/userspace-api/media/v4l/ext-ctrls-flash.rst | 5 +++++
> >  1 file changed, 5 insertions(+)
> > 
> > diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-flash.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-flash.rst
> > index d22c5efb806a183a3ad67ec3e6550b002a51659a..03a58ef94be7c870f55d5a9bb09503995dbfb402 100644
> > --- a/Documentation/userspace-api/media/v4l/ext-ctrls-flash.rst
> > +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-flash.rst
> > @@ -186,3 +186,8 @@ Flash Control IDs
> >      charged before strobing. LED flashes often require a cooldown period
> >      after strobe during which another strobe will not be possible. This
> >      is a read-only control.
> > +
> > +``V4L2_CID_FLASH_DURATION (integer)``
> > +    Duration the flash should be on when the flash LED is in flash mode
> > +    (V4L2_FLASH_LED_MODE_FLASH). The unit should be microseconds (µs)
> > +    if possible.
> > 
> 
> If this control is present, does that mean that the flash duration always have
> to be set manually? Or can there be an 'Auto' mode as well? And if so, how is
> that set?

To be honest I haven't thought about automatic flash duration. Is this
something which is required?

At least for the ov9282 sensor (which I've implemented this control for
in this series) there is no "auto" mode AFAIK.

If it's required: What would be the best solution?
Extending V4L2_CID_FLASH_LED_MODE with a new menu option? E.g.
V4L2_FLASH_LED_MODE_FLASH_{MANUAL,AUTO}?

> 
> Regards,
> 
> 	Hans

Thanks!
Richard