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([2a01:e0a:c:37e0:ced3:55bd:f454:e722]) by smtp.gmail.com with ESMTPSA id f18-20020adffcd2000000b00317b5c8a4f1sm2193477wrs.60.2023.09.08.07.06.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 08 Sep 2023 07:06:35 -0700 (PDT) Message-ID: Date: Fri, 8 Sep 2023 16:06:34 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH v3] drm/plane: Add documentation about software color conversion. To: Javier Martinez Canillas , Thomas Zimmermann , Maxime Ripard References: <20230825140434.182664-1-jfalempe@redhat.com> <3f1bd1ad-cd1f-515d-38bd-63e412dec286@suse.de> <5ltuqgsepffvp6rjvmskqtvzyyhvk6phmixm3crfteznyejn4t@mtycsppney5x> <87ledg3hib.fsf@minerva.mail-host-address-is-not-set> From: Jocelyn Falempe In-Reply-To: <87ledg3hib.fsf@minerva.mail-host-address-is-not-set> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: dri-devel@lists.freedesktop.org, ppaalanen@gmail.com, airlied@redhat.com Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On 08/09/2023 15:46, Javier Martinez Canillas wrote: > Thomas Zimmermann writes: > > Hello Thomas, > >> Hi Maxime >> >> Am 08.09.23 um 12:58 schrieb Maxime Ripard: >>> Hi, >>> >>> On Fri, Sep 08, 2023 at 11:21:51AM +0200, Thomas Zimmermann wrote: >>>> Am 25.08.23 um 16:04 schrieb Jocelyn Falempe: >>>> [...] >>>>> + * >>>>> + * But there are two exceptions only for dumb buffers: >>>>> + * * To support XRGB8888 if it's not supported by the hardware. >>>> >>>> >>>>> + * * Any driver is free to modify its internal representation of the format, >>>>> + * as long as it doesn't alter the visible content in any way, and doesn't >>>>> + * modify the user-provided buffer. An example would be to drop the >>>>> + * padding component from a format to save some memory bandwidth. >>>> >>>> I have strong objections to this point, _especially_ as you're apparently >>>> trying to sneak this in after our discussion. >>> >>> I think it's an unfair characterization. This was discussed on >>> #dri-devel, and went through several rounds over the mailing lists, with >>> you in Cc for each. How is that sneaking something in? >> >> A few months ago, we had a flamewar'ish IRC discussion on format >> conversion within the kernel. The general sentiment was that the kernel >> drivers should use what ever is provided by userspace without further >> processing. The short argument was 'userspace knows better'. The only >> exception is for supporting XRGB8888 on hardware that would otherwise >> not support it. After some consideration, I agree with all that. (Back >> then I didn't.) I wasn't part of this "flamewar", and though my patch was a bit unrelated to this. That's why I started this work to document clearly what is acceptable in the kernel or not. I discuss it on IRC, and then proposed the patch on dri-devel to find a compromise, and see if my case can be acceptable or not. >> >> A few weeks ago I received a patch to do an implicit conversion from >> XRGB8888 to RGB888 within mgag200. [1] I don't have a link to the >> discussion, but I NAK'ed that patch pretty hard on IRC by following that >> other discussion. >> >> And know I find that this patch (even in its v1) contains language that >> retroactively legitimizes the mgag200 patch. I wrote 'apparently' I my >> reply, as I assume that there's more to it, but how does it not look >> like an attempt to sneak in something that is known to be controversial? >> That was not my intention, and I apologize if you feel it this way. My goal was just to clarify if this optimization is acceptable for other kernel developers, since I though you were willing to accept it, but some other developers from the "flamewar" were against. > > While is true that the motivation for Jocelyn's patch was to make explicit > what are the rules with regard to drivers emulating formats (other than > "we had a flamewar on IRC a while back" which is quite ambiguous), it was > not attempt to sneak something that is known to be controversial. > > In fact, it is an attempt to dispel the controversy and document what is > acceptable and what is not for a driver. > >> It might have been better to discuss the question separately on the >> dri-devel ML. Maybe we can do this here. >> > > This was discussed in the #dri-devel IRC channel, I believe you were on > PTO at the time and probably that's why you missed. I found the logs here: > > https://people.freedesktop.org/~cbrill/dri-log/?channel=dri-devel&date=2023-08-04 > > As you can see there, most people agreed that what Jocelyn wrote in his > doc patch is the most pragmatic compromise. > Best regards, -- Jocelyn