linux-kernel - Re: [PATCH v5 06/10] media: i2c: ov9282: add led

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Message-ID: <f4owcdddwjar6lg5f2urpaynykks4yrttto7h7qfnodmqg22ll@xl45pbhuyhmx>
Date: Fri, 11 Jul 2025 09:41:52 +0200
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>, Hans Verkuil <hverkuil@...all.nl>, linux-media@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-leds@...r.kernel.org
Subject: Re: [PATCH v5 06/10] media: i2c: ov9282: add led_mode v4l2 control

Hi Sakari,

On Thu, Jul 10, 2025 at 08:14:07AM +0000, Sakari Ailus wrote:
> Hi Richard,
> 
> On Thu, Jul 10, 2025 at 08:50:24AM +0200, Richard Leitner wrote:
> > Hi Sakari,
> > 
> > thanks for the feedback :)
> > 
> > On Wed, Jul 09, 2025 at 09:12:57PM +0000, Sakari Ailus wrote:
> > > Hi Richard,
> > > 
> > > Thanks for the update.
> > > 
> > > On Tue, Jun 17, 2025 at 09:31:40AM +0200, Richard Leitner wrote:
> > > > Add V4L2_CID_FLASH_LED_MODE support using the "strobe output enable"
> > > > feature of the sensor. This implements following modes:
> > > > 
> > > >  - V4L2_FLASH_LED_MODE_NONE, which disables the strobe output
> > > >  - V4L2_FLASH_LED_MODE_FLASH, which enables the strobe output
> > > 
> > > I really think you should use a different control for this. The sensor can
> > > strobe the flash but it won't control its mode.
> > > 
> > > How about calling it V4L2_FLASH_STROBE_ENABLE?
> > 
> > I agree on that. But tbh V4L2_FLASH_STROBE_ENABLE somehow sounds wrong
> > to me. As the strobe output in the ov9282 case goes high for the strobe
> > duration, what do you think about calling it V4L2_FLASH_STROBE_PULSE?
> 
> That's how the hardware strobe is supposed to work, there's nothing unusual
> in that. How about V4L2_FLASH_HW_STROBE_ENABLE?

Ah. Sorry. I believe I completely misunderstood your previous point.
You're not referring to a new menu entry in V4L2_CID_FLASH_LED_MODE,
but rather proposing a completely new boolean control, correct?

As this would be separating the V4L2_CID's of "strobe signal source"
(aka sensor) and "strobe signal consumer" (aka flash device/LEDs), that
makes perfect sense to me now! :)

What are your thoughts on naming it V4L2_FLASH_HW_STROBE_SIGNAL?

The main reason behind removing the "ENABLE" suffix is that none of
the V4L2_CID_FLASH_* controls currently include "ENABLE" in their
names. Altough, for example, V4L2_CID_FLASH_CHARGE performs a
similar function (en-/disabling the charging of the capacitor).

On the other hand, adding "SIGNAL" to the control name, in my opinion,
makes it clearer that it only enables a signal and not some kind of
flash device or LED.

> 
> > Or should it be V4L2_FLASH_LED_MODE_STROBE_PULSE?
> > 
> > Regarding disabling the strobe output: Is sticking with V4L2_FLASH_LED_MODE_NONE
> > fine? Or do you prefer an additional V4L2_FLASH_(MODE_)STROBE_DISABLE
> > or something similar?
> 
> This isn't about the LED flash mode and we shouldn't suggest it is.

Thanks for the clarification. I guess I got your point now :)

regards;rl

> 
> -- 
> Regards,
> 
> Sakari Ailus