From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) (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 9070D21D3F8; Fri, 7 Nov 2025 23:34:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.167.242.64 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762558465; cv=none; b=qyenauKS9L6GUxsJ/0siqvuF7Hl/D930EXnWjkprjzrFhuwXUJDjCa8spr5nmpWjk58fyt+Tlaby+40LOkdXqJr4z27tUEiTowBl47w1JLrKuutHf0qn9W4lFGOswl4th/6qNuHThMSWozUns1wOdTALFtPaxJRFfeE19APso/c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762558465; c=relaxed/simple; bh=v+aqR0oFDtbY2RGxbmZS4i8tsceD2wMT6FgrKxFkNuE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=IPh+P6m4zHXhub7OMA55paY1oV+vCd0ceVaxeKQR4unluD0GKDijXBHkA+PXEE4J1e4GUN0hiD8ckk9hWKkxulHwIREPcs5eVZI3lIlYmNb+CYr/y6ueIEpdvNrQbRfwaosiif19JN3pkDfkAqEwhF/bMdVKVjM7EV5b9CeswbI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=ideasonboard.com; spf=pass smtp.mailfrom=ideasonboard.com; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b=ez+Kc6Zz; arc=none smtp.client-ip=213.167.242.64 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="ez+Kc6Zz" Received: from pendragon.ideasonboard.com (82-203-161-95.bb.dnainternet.fi [82.203.161.95]) by perceval.ideasonboard.com (Postfix) with UTF8SMTPSA id 129F1A8F; Sat, 8 Nov 2025 00:32:24 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1762558345; bh=v+aqR0oFDtbY2RGxbmZS4i8tsceD2wMT6FgrKxFkNuE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ez+Kc6Zz2r29s2sYFBQG5meYqDQS0uR06fGd3xSE43sTrHVbruW1AMszX9TAleTON u4RbeQ8JObhaehHFv3VGDLcKakJ5LehXpt9KkbYsUSV7k7MVrQAO9q0GNU73VX/6Ib 4nJS82/EDBUunMnuyX6kPqAVpNiBvhX7KnNyXuzo= Date: Sat, 8 Nov 2025 01:34:15 +0200 From: Laurent Pinchart To: Jacopo Mondi Cc: Dafna Hirschfeld , Keke Li , Mauro Carvalho Chehab , Heiko Stuebner , Dan Scally , Sakari Ailus , Antoine Bouyer , linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, linux-rockchip@lists.infradead.org, linux-arm-kernel@lists.infradead.org, Michael Riesch Subject: Re: [PATCH v8 8/8] media: Documentation: kapi: Add v4l2 generic ISP support Message-ID: <20251107233415.GK5558@pendragon.ideasonboard.com> References: <20251020-extensible-parameters-validation-v8-0-afba4ba7b42d@ideasonboard.com> <20251020-extensible-parameters-validation-v8-8-afba4ba7b42d@ideasonboard.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20251020-extensible-parameters-validation-v8-8-afba4ba7b42d@ideasonboard.com> Hi Jacopo, Thank you for the patch. On Mon, Oct 20, 2025 at 10:24:54AM +0200, Jacopo Mondi wrote: > Add to the driver-api documentation the v4l2-isp.h types and > helpers documentation. > > Reviewed-by: Daniel Scally > Reviewed-by: Michael Riesch > Acked-by: Sakari Ailus > Signed-off-by: Jacopo Mondi > --- > Documentation/driver-api/media/v4l2-core.rst | 1 + > Documentation/driver-api/media/v4l2-isp.rst | 49 ++++++++++++++++++++++++++++ > MAINTAINERS | 1 + > 3 files changed, 51 insertions(+) > > diff --git a/Documentation/driver-api/media/v4l2-core.rst b/Documentation/driver-api/media/v4l2-core.rst > index ad987c34ad2a8460bb95e97adc4d850d624e0b81..a5f5102c64cca57b57b54ab95882b26286fb27de 100644 > --- a/Documentation/driver-api/media/v4l2-core.rst > +++ b/Documentation/driver-api/media/v4l2-core.rst > @@ -27,3 +27,4 @@ Video4Linux devices > v4l2-common > v4l2-tveeprom > v4l2-jpeg > + v4l2-isp > diff --git a/Documentation/driver-api/media/v4l2-isp.rst b/Documentation/driver-api/media/v4l2-isp.rst > new file mode 100644 > index 0000000000000000000000000000000000000000..150ba39b257b23e6a8ca1a348047f5b55588fbf7 > --- /dev/null > +++ b/Documentation/driver-api/media/v4l2-isp.rst > @@ -0,0 +1,49 @@ > +.. SPDX-License-Identifier: GPL-2.0 > + > +V4L2 generic ISP parameters and statistics support > +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > + > +Design rationale > +================ > + > +ISP configuration parameters and statistics are processed and collected by > +drivers and exchanged with userspace through data types that usually > +reflect the ISP peripheral registers layout. > + > +Each ISP driver defines its own metadata output format for parameters and > +a metadata capture format for statistics. The buffer layout is realized by a > +set of C structures that reflects the registers layout. The number and types > +of C structures is fixed by the format definition and becomes part of the Linux > +kernel uAPI/uABI interface. > + > +Because of the hard requirement of backward compatibility when extending the > +user API/ABI interface, modifying an ISP driver capture or output metadata > +format after it has been accepted by mainline is very hard if not impossible. > + > +It generally happens, in fact, that after the first accepted revision of an ISP > +driver the buffers layout need to be modified, either to support new hardware > +blocks, to fix bugs or to support different revisions of the hardware. > + > +Each of these situations would require defining a new metadata format, making it > +really hard to maintain and extend drivers and requiring userspace to use > +the correct format depending on the kernel revision in use. > + > +V4L2 ISP configuration parameters > +================================= > + > +For these reasons, Video4Linux2 defines generic types for ISP configuration > +parameters and statistics. Drivers are still expected to define their own > +formats for their metadata output and capture nodes, but the buffers layout can > +be defined using the extensible and versioned types defined by > +include/uapi/linux/media/v4l2-isp.h. > + > +Drivers are expected to provide the definitions of their supported ISP blocks, > +the control flags and the expected maximum size of a buffer. What are the control flags here ? Is it a leftover from a previous version ? With this addressed, Reviewed-by: Laurent Pinchart > + > +For driver developers a set of helper functions to assist them with validation > +of the buffer received from userspace is available in > +drivers/media/v4l2-core/v4l2-isp.c > + > +V4L2 ISP support driver documentation > +===================================== > +.. kernel-doc:: include/media/v4l2-isp.h > diff --git a/MAINTAINERS b/MAINTAINERS > index 5833f82caa7f2f734bb0e1be144ade2109b23988..cd1137c7754538d02bd72521fec6c89e082246d2 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -26856,6 +26856,7 @@ V4L2 GENERIC ISP PARAMETERS AND STATISTIC FORMATS > M: Jacopo Mondi > L: linux-media@vger.kernel.org > S: Maintained > +F: Documentation/driver-api/media/v4l2-isp.rst > F: Documentation/userspace-api/media/v4l/v4l2-isp.rst > F: drivers/media/v4l2-core/v4l2-isp.c > F: include/media/v4l2-isp.h -- Regards, Laurent Pinchart