linux-kernel - Re: [PATCH v2 1/8] media: v4l: ctrls: add a control for flash/strobe duration

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Message-ID: <4un43tc6jdwyueefqyjyk7yzh34366uhakimtoat2lhutm3myn@ero3pn22qfm7>
Date: Tue, 25 Mar 2025 09:20:29 +0100
From: Richard Leitner <richard.leitner@...ux.dev>
To: Sakari Ailus <sakari.ailus@...ux.intel.com>
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
Subject: Re: [PATCH v2 1/8] media: v4l: ctrls: add a control for flash/strobe
 duration

Hi Dave, Hi Sakari

On Wed, Mar 19, 2025 at 10:06:28AM +0000, Sakari Ailus wrote:
> Hi Dave,
> 
> On Tue, Mar 18, 2025 at 04:39:05PM +0000, Dave Stevenson wrote:
> > Hi Sakari
> > 
> > On Tue, 18 Mar 2025 at 15:11, Sakari Ailus <sakari.ailus@...ux.intel.com> wrote:
> > >
> > > Hi Richard,
> > >
> > > On Tue, Mar 18, 2025 at 03:46:18PM +0100, Richard Leitner wrote:

...

> > > > The ov9282 driver uses the sensor in global shutter mode.
> > > >
> > > > I totally agree with your statement. This pattern is only useful for
> > > > global shutter operation.
> > >
> > > I think (nearly?) all supported sensors use a rolling shutter.
> > 
> > You've got at least two other global shutter sensors supported in
> > mainline - Omnivision ov7251 and Sony imx296.
> > Patches have been posted for OnSemi ar0144 (Laurent) and ar0234
> > (Dongcheng), which are also both global shutter sensors.
> > 
> > So yes they are in the minority, but not that uncommon.
> 
> Thanks for the list. I briefly discussed this with Laurent and I agree with
> him this information would probably be best kept with userspace (libcamera)
> without trying to enumerate it from the kernel (albeit CCS might be an
> exception, but that's an entirely different discussion then). Only changing
> the global/rolling configuration would require a control.

Thanks for the feeback and clarification!

So am I understanding this correctly that the flash/strobe duration
approach in this series is basically fine?

If so I will send a v3 later today.

regards;rl

> 
> -- 
> Regards,
> 
> Sakari Ailus