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[83.233.6.197]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-54c4566dc80sm53867e87.192.2025.04.08.23.41.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 08 Apr 2025 23:41:49 -0700 (PDT) Date: Wed, 9 Apr 2025 08:41:47 +0200 From: Marcus Folkesson To: Javier Martinez Canillas Cc: David Airlie , Simona Vetter , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , Rob Herring , Krzysztof Kozlowski , Conor Dooley , dri-devel@lists.freedesktop.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Thomas Zimmermann Subject: Re: [PATCH v3 2/3] drm/st7571-i2c: add support for Sitronix ST7571 LCD controller Message-ID: References: <20250408-st7571-v3-0-200693efec57@gmail.com> <20250408-st7571-v3-2-200693efec57@gmail.com> <87cydn9bkx.fsf@minerva.mail-host-address-is-not-set> <87ecy1g8z8.fsf@minerva.mail-host-address-is-not-set> Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="Ylj4ERT0Ocye4RUt" Content-Disposition: inline In-Reply-To: <87ecy1g8z8.fsf@minerva.mail-host-address-is-not-set> --Ylj4ERT0Ocye4RUt Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hello Javier, On Wed, Apr 09, 2025 at 08:11:23AM +0200, Javier Martinez Canillas wrote: [...] > >> > +static int st7571_set_pixel_format(struct st7571_device *st7571, > >> > + u32 pixel_format) > >> > +{ > >> > + switch (pixel_format) { > >> > + case DRM_FORMAT_C1: > >> > + return st7571_set_color_mode(st7571, ST7571_COLOR_MODE_BLACKWHITE= ); > >> > + case DRM_FORMAT_C2: > >> > + return st7571_set_color_mode(st7571, ST7571_COLOR_MODE_GRAY); > >> > + default: > >> > + return -EINVAL; > >> > + } > >>=20 > >> These should be DRM_FORMAT_R1 and DRM_FORMAT_R2 and not C{1,2}. The fo= rmer > >> is for displays have a single color (i.e: grey) while the latter is wh= en a > >> pixel can have different color, whose values are defined by a CLUT tab= le. > >>=20 > > > > I see. > > Does fbdev only works with CLUT formats? I get this error when I switch > > to DRM_FORMAT_R{1,2}: > > > > [drm] Initialized st7571 1.0.0 for 0-003f on minor 0 > > st7571 0-003f: [drm] format C1 little-endian (0x20203143) not support= ed > > st7571 0-003f: [drm] No compatible format found > > st7571 0-003f: [drm] *ERROR* fbdev: Failed to setup emulation (ret=3D-2= 2) > > > > >=20 > That's a god question, I don't really know... >=20 > But fbdev does support XRGB8888, which may be another good reason to add > it and make it the default format. Yes, it will cause an unnecessary pixel > format conversion but the I2C transport is so slow anyways that compute is > not the bottleneck when using these small displays. Hrm, I now realised that I have another issue. Not all LCDs that will be attached to the ST7571 controller will be grayscale. The display I've attached to the ST7571 is a monochrome LCD for example. Maybe the right way to do it is to only support XRGB8888 and specify=20 if the display is monochrome or grayscale in the device tree. Or do you have any good suggestions? [...] >=20 > --=20 > Best regards, >=20 > Javier Martinez Canillas > Core Platforms > Red Hat >=20 Best regards, Marcus Folkesson --Ylj4ERT0Ocye4RUt Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEBVGi6LZstU1kwSxliIBOb1ldUjIFAmf2FqcACgkQiIBOb1ld UjJlFA/+Mvgnw0GHgT/CbvHMZfsKrzVui9dIXTaP9ruHztPyzxKfhzb/VOxWIqm2 Grdh3t1Q2HqElAM/cpET2LpPRej5WHklHoah93ATdVsE29LDwkULtRSqAND7laJc FGjvEM23bcXSeToZ7kvJZHYziu3ABhJKtGmGOKGfUFOPg7LOvdpkBWxj2dzni/mq 02OVArtj0gmMvdyQDXBLrAVN0OvbWCc0IIDlVfQ6EiZeag/Kefqt57kL02y2ffVo OR7DHz2QrkPJLzK61dfVwA3uMC+RP6S5a+nGcB+Qw5z0KMkiO7S8hOIOxoyW+eF2 FFrPjv1fnPZPjjfulVcKJHAk84hqOiyTnll9YDUMefB0BrwYCtTc56CKa+abATuH trbrdtDY6BnKSNN/fzwkHeKtRwWoISvJ1s+WcO5bf2nsA751uuxpVXV/xy+ZrMZ/ IIraaNw+mHPpCeUZW+bjf9sSiGvGKjBiWFQGCCUiEzbbhnd4CQcLl0N61umLWjZT 3IAY67lI0vk5Bms0wJnP1vZwop9c8MX7GVK6gd+5fy5q1AXa/sVAQsz74rwaLyX9 uErGQKENWaTdlVes8hzJUOSIlgamh9M+P/H29qGfaQqCfI6UkdH+qFowo3JV0A/j OQOe8CHsfLkesxn7/18YT3eiP7PPOR+TuapvXPoSCBLQjzmBajs= =oJhl -----END PGP SIGNATURE----- --Ylj4ERT0Ocye4RUt--