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[62.151.111.63]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-485883953cfsm41228794f8f.13.2026.09.10.01.10.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 10 Sep 2026 01:10:04 -0700 (PDT) From: Javier Martinez Canillas To: Thomas Zimmermann , ardb@kernel.org, ilias.apalodimas@linaro.org, jani.nikula@linux.intel.com, maarten.lankhorst@linux.intel.com, mripard@kernel.org, simona@ffwll.ch, airlied@gmail.com Cc: dri-devel@lists.freedesktop.org, linux-efi@vger.kernel.org, sashiko-reviews@lists.linux.dev, Thomas Zimmermann Subject: Re: [PATCH v4 2/3] drm/edid: Add drm_edid_detect_panel_size() In-Reply-To: <20260904090850.43060-3-tzimmermann@suse.de> References: <20260904090850.43060-1-tzimmermann@suse.de> <20260904090850.43060-3-tzimmermann@suse.de> Date: Thu, 10 Sep 2026 10:10:03 +0200 Message-ID: <87y0d9cysk.fsf@ocarina.mail-host-address-is-not-set> Precedence: bulk X-Mailing-List: linux-efi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain Thomas Zimmermann writes: > Add drm_edid_detect_panel_size() to extract the panel's preferred > display resolution from a given EDID. Required for setting up DRM's > panel orientation quirks in sysfb drivers. > > v4: > - fix test for EDID PTD (Jani) > v3: > - mention use case in documentation (Jani) > - use is_detailed_timing_descriptor() (Jani) > - rename helper to drm_edid_detect_panel_size() > v2: > - handle EDID without pixel timing descriptor (Sashiko) > - fix checks for width and height pointers > > Signed-off-by: Thomas Zimmermann > Acked-by: Ard Biesheuvel > --- > drivers/gpu/drm/drm_edid.c | 47 ++++++++++++++++++++++++++++++++++++++ > include/drm/drm_edid.h | 2 ++ > 2 files changed, 49 insertions(+) > > diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c > index 9990a836d0b6..1331efb4876c 100644 > --- a/drivers/gpu/drm/drm_edid.c > +++ b/drivers/gpu/drm/drm_edid.c > @@ -7852,3 +7852,50 @@ bool drm_edid_is_digital(const struct drm_edid *drm_edid) > drm_edid->edid->input & DRM_EDID_INPUT_DIGITAL; > } > EXPORT_SYMBOL(drm_edid_is_digital); > + > +/** > + * drm_edid_detect_panel_size - Get a panel's size from EDID > + * @drm_edid: EDID of the panel. > + * @width: Returns the panel's width in pixels per scanline, if given > + * @height: Returns the panel's height in scanlines, if given > + * > + * This function detects the preferred size of a panel from the given > + * EDID. There is no such information stored in the EDID block directly, > + * but the preferred mode often corresponds to the panel's native geometry. > + * > + * This helper should only be used during initialization before the > + * connector is available. For regular use, retrieve the available display > + * modes with the connector functions. > + * > + * Return: Zero on success, or a negative errno code otherwise. > + */ > +int drm_edid_detect_panel_size(const struct drm_edid *drm_edid, > + unsigned int *width, unsigned int *height) > +{ > + const struct edid *edid = drm_edid->edid; > + const struct detailed_timing *dt; > + const struct detailed_pixel_timing *pt; > + > + /* > + * Use display mode from the Preferred Timing Descriptor. For old > + * and obscure displays, we might need better heuristics. > + */ > + > + if (edid->revision < 4 || !(edid->features & DRM_EDID_FEATURE_PREFERRED_TIMING)) > + return -EINVAL; /* no Preferred Timing Descriptor */ > + I saw that Jani and you discussed this logic in v3. I originally thought that your v3 was correct and this one was wrong, but I noticed now that this flag changed its semantic between 1.3 and 1.4. So I think that this latest version is correct indeed, 1.3 didn't include the native pixel format and 1.4 does not either if DRM_EDID_FEATURE_PREFERRED_TIMING flag is not set. Reviewed-by: Javier Martinez Canillas -- Best regards, Javier Martinez Canillas Core Platforms Red Hat