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R. A. Prado" To: Pekka Paalanen , Harry Wentland Cc: Shengyu Qu , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Chun-Kuang Hu , Philipp Zabel , Matthias Brugger , AngeloGioacchino Del Regno , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org, linux-arm-kernel@lists.infradead.org, daniels@collabora.com, ariel.dalessandro@collabora.com, kernel@collabora.com, xaver.hugl@gmail.com Date: Fri, 06 Feb 2026 08:28:14 -0500 In-Reply-To: <20260206110901.660cf712@eldfell> References: <20251223-mtk-ovl-pre-blend-colorops-v1-0-0cb99bd0ab33@collabora.com> <20260206110901.660cf712@eldfell> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2-8 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ZohoMailClient: External On Fri, 2026-02-06 at 11:09 +0200, Pekka Paalanen wrote: > On Fri, 2 Jan 2026 13:40:21 -0500 > Harry Wentland wrote: >=20 > > On 2026-01-01 07:37, Shengyu Qu wrote: > > >=20 > > >=20 > > > =E5=9C=A8 2025/12/30 02:53, Shengyu Qu =E5=86=99=E9=81=93:=C2=A0=20 > > > >=20 > > > >=20 > > > > =E5=9C=A8 2025/12/24 3:44, N=C3=83 colas F. R. A. Prado =E5=86=99= =E9=81=93:=C2=A0=20 >=20 > > > > > Given the lack of support for writeback connectors on the > > > > > MediaTek KMS driver, combined with limited hardware > > > > > documentation, I haven't been able to verify the correctness > > > > > of > > > > > each curve, only that they were visually sane (gamma curves > > > > > made > > > > > the image on the display brighter, while inverse gamma made > > > > > it > > > > > darker).=C2=A0=20 > > > >=20 > > > > Hmmm I don't think this is acceptable. sRGB/scRGB has two > > > > transfer > > > > functions mentioned in original specification[1]. To keep color > > > > accuracy, we need someone from mediatek confirm whether this is > > > > piece- wise or pure power 2.2 transfer function, this is > > > > already > > > > done in original amdgpu color pipeline series, sRGB means > > > > piece-wise while also dedicated power 2.2 function exists.=C2=A0= =20 > >=20 > > Not sure what you mean with this not being acceptable. This is > > about > > enabling HW support for this functionality. Not every HW has > > writeback for testing. At some point you'll have to trust the > > driver > > devs if you're going to use functionality of the driver. We're not > > always going to get everything perfect, but if that's really such a > > worry you can always use shaders to do precisely what you want. > >=20 >=20 > Hi Harry, >=20 > yes, but I understood that in this case, the hardware documentation > available is so vague that it's impossible to say what it will > actually > do. There are no formulas given or referenced in the documentation, > are > there, N=C3=ADcolas? No formulas at all, the only documentation I had available for the curves was the register definition, which simply lists the possible values: SCRGB, BT709, BT2020, HLG. --=20 Thanks, N=C3=ADcolas