On Fri, 04 Sep 2026, Thomas Zimmermann <[email protected]> wrote: > 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 <[email protected]> > Acked-by: Ard Biesheuvel <[email protected]>
Given my shoddy comments before, not sure what it's worth, but, Reviewed-by: Jani Nikula <[email protected]> > --- > 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 */ > + > + dt = &edid->detailed_timings[0]; > + > + if (!is_detailed_timing_descriptor(dt)) > + return -EINVAL; > + > + pt = &dt->data.pixel_data; > + > + if (width) > + *width = (pt->hactive_hblank_hi & 0xf0) << 4 | pt->hactive_lo; > + if (height) > + *height = (pt->vactive_vblank_hi & 0xf0) << 4 | pt->vactive_lo; > + > + return 0; > +} > +EXPORT_SYMBOL(drm_edid_detect_panel_size); > diff --git a/include/drm/drm_edid.h b/include/drm/drm_edid.h > index 04f7a7f1f108..a2617aa34edf 100644 > --- a/include/drm/drm_edid.h > +++ b/include/drm/drm_edid.h > @@ -490,5 +490,7 @@ u32 drm_edid_get_panel_id(const struct drm_edid > *drm_edid); > bool drm_edid_match(const struct drm_edid *drm_edid, > const struct drm_edid_ident *ident); > bool drm_edid_has_quirk(struct drm_connector *connector, enum drm_edid_quirk > quirk); > +int drm_edid_detect_panel_size(const struct drm_edid *drm_edid, > + unsigned int *width, unsigned int *height); > > #endif /* __DRM_EDID_H__ */ -- Jani Nikula, Intel
