Add drm_edid_get_preferred_size() to extract the panel's preferred display resolution from a given EDID. Required for DRM's panel orientation quirks.
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 | 46 ++++++++++++++++++++++++++++++++++++++ include/drm/drm_edid.h | 2 ++ 2 files changed, 48 insertions(+) diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c index 9990a836d0b6..53c7eed7a73e 100644 --- a/drivers/gpu/drm/drm_edid.c +++ b/drivers/gpu/drm/drm_edid.c @@ -2872,6 +2872,52 @@ u32 drm_edid_get_panel_id(const struct drm_edid *drm_edid) } EXPORT_SYMBOL(drm_edid_get_panel_id); +/** + * drm_edid_get_preferred_size - Get a panel's preferred size from EDID + * @drm_edid: EDID that contains panel ID. + * @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. + * + * Return: Zero on success, or a negative errno code otherwise. + */ +int drm_edid_get_preferred_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; + + if (drm_edid->size < EDID_LENGTH) + return -EINVAL; + + /* + * 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 (!le16_to_cpu(dt->pixel_clock)) + 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_get_preferred_size); + /** * drm_edid_read_base_block - Get a panel's EDID base block * @adapter: I2C adapter to use for DDC diff --git a/include/drm/drm_edid.h b/include/drm/drm_edid.h index 04f7a7f1f108..981aeeb6ddf9 100644 --- a/include/drm/drm_edid.h +++ b/include/drm/drm_edid.h @@ -487,6 +487,8 @@ void drm_edid_get_product_id(const struct drm_edid *drm_edid, void drm_edid_print_product_id(struct drm_printer *p, const struct drm_edid_product_id *id, bool raw); u32 drm_edid_get_panel_id(const struct drm_edid *drm_edid); +int drm_edid_get_preferred_size(const struct drm_edid *drm_edid, + unsigned int *width, unsigned int *height); 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); -- 2.55.0
