From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-179.mta0.migadu.com (out-179.mta0.migadu.com [91.218.175.179]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 66B6C30DD0D for ; Mon, 1 Sep 2025 10:44:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.179 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756723469; cv=none; b=qwxdVSNk/vFuFlAxiZhfR8ZmDowx+ndQHdry6Um4R0FWy5tGpyUbuI09JnHEKDLkxVsGyDkMAAHdEXUKcGBB8toKoLY5sz5PGwZOl7vHNJ+1tUfHYfhBRkqFRlu0W8czTudfQFSc17usca96sfElSxrD0GgPW6jtWOtW24VOv1c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756723469; c=relaxed/simple; bh=6THE98mcDom9w0YncY2cuBO0AEoX8fSOu4k2kwNBuxY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=NCQF9vvFAMgeHeag3Z+1Rwz3POQLcUNJYY/AiJ3dtQBBYsZZCcbxsc928g/7Sx7S7dtzAD9OOK6gOyDKwMapah+XkQ05LWFn3pCa8S8MzwJK48eAqXFOjZ9oihzvMMCxe5gjmCHLQ+jdDonYKDWfCsZXI/bNGIyYtO9JRVbPFv8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=h3kw5ZHy; arc=none smtp.client-ip=91.218.175.179 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="h3kw5ZHy" Date: Mon, 1 Sep 2025 12:44:07 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1756723455; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=5S4fuRk+bvbyu3AGCXqWWILKtUl2HbqJIAPTs34e4wg=; b=h3kw5ZHyQ6ph/2Enddeqos4frNf3RhMiFacv4NTFlgzHayIdK79JES6w5APQtac8+iGVRw 5wb1DrMnIVTYbqFPyUApEMYCzqgrqTKVYzXcx4QT/ofN+6gsBuf9QVXE+NZHIAHY+iKDUQ LW0hLe3LcpS/VcLo/XSux9RlQHKXelU= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Richard Leitner To: Sakari Ailus Cc: Dave Stevenson , Mauro Carvalho Chehab , Lee Jones , Pavel Machek , Laurent Pinchart , Hans Verkuil , linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, linux-leds@vger.kernel.org Subject: Re: [PATCH v6 03/11] Documentation: uAPI: media: add V4L2_CID_FLASH_DURATION Message-ID: References: <20250716-ov9282-flash-strobe-v6-0-934f12aeff33@linux.dev> <20250716-ov9282-flash-strobe-v6-3-934f12aeff33@linux.dev> Precedence: bulk X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Migadu-Flow: FLOW_OUT On Mon, Aug 25, 2025 at 08:42:17AM +0300, Sakari Ailus wrote: > Hi Richard, > > Thanks for the update (and for the ping!). > > On Wed, Jul 16, 2025 at 11:06:53AM +0200, Richard Leitner wrote: > > Add the new strobe_duration control to v4l uAPI documentation. > > > > Signed-off-by: Richard Leitner > > --- > > 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. > > > > I think we should add this is related to the hardware strobe. > > How about: > > ``V4L2_CID_FLASH_DURATION (integer)`` > > Duration of the flash strobe from the strobe source, typically a camera > sensor. Controlling the flash LED strobe length this way requires that the > flash LED driver's :ref:`flash LED mode ` is set > to ``V4L2_FLASH_LED_MODE_FLASH`` and :ref:`strobe source > ` is set to ``V4L2_FLASH_STROBE_SOURCE_EXTERNAL``. > The unit should be microseconds (µs) if possible. > > This requires of course the appropriate labels. > > I also wonder whether we should use 0,1 µs or even ns for the unit. Thanks for the pointer. I did a quick internet search and the shortest flash duration of speedlights/studio strobes I found was Profoto D2 with 1/63000 sec ~> 15.9µs. So I IMHO we are fine with 1µs resolution here. regards;rl > > -- > Kind regards, > > Sakari Ailus