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.
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]> --- 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..d5d9e77dc91b 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__ */ -- 2.55.0
