drm: handle override and firmware EDID at drm_do_get_edid() level

Handle debugfs override edid and firmware edid at the low level to
transparently and completely replace the real edid. Previously, we
practically only used the modes from the override EDID, and none of the
other data, such as audio parameters.

This change also prevents actual EDID reads when the EDID is to be
overridden, but retains the DDC probe. This is useful if the reason for
preferring override EDID are problems with reading the data, or
corruption of the data.

Move firmware EDID loading from helper to core, as the functionality
moves to lower level as well. This will result in a change of module
parameter from drm_kms_helper.edid_firmware to drm.edid_firmware, which
arguably makes more sense anyway.

Some future work remains related to override and firmware EDID
validation. Like before, no validation is done for override EDID. The
firmware EDID is validated separately in the loader. Some unification
and deduplication would be in order, to validate all of them at the
drm_do_get_edid() level, like "real" EDIDs.

v2: move firmware loading to core

v3: rebase, commit message refresh

Cc: Abdiel Janulgue <abdiel.janulgue@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Tested-by: Abdiel Janulgue <abdiel.janulgue@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Acked-by: Dave Airlie <airlied@gmail.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1e8a710bcac46e5136c1a7b430074893c81f364a.1505203831.git.jani.nikula@intel.com

1 files changed, 15 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 6bb6337be920..00ddabfbf980 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -1533,6 +1533,10 @@ static void connector_bad_edid(struct drm_connector *connector,
  * level, drivers must make all reasonable efforts to expose it as an I2C
  * adapter and use drm_get_edid() instead of abusing this function.
  *
+ * The EDID may be overridden using debugfs override_edid or firmare EDID
+ * (drm_load_edid_firmware() and drm.edid_firmware parameter), in this priority
+ * order. Having either of them bypasses actual EDID reads.
+ *
  * Return: Pointer to valid EDID or NULL if we couldn't find any.
  */
 struct edid *drm_do_get_edid(struct drm_connector *connector,
@@ -1542,6 +1546,17 @@ struct edid *drm_do_get_edid(struct drm_connector *connector,
 {
 	int i, j = 0, valid_extensions = 0;
 	u8 *edid, *new;
+	struct edid *override = NULL;
+
+	if (connector->override_edid)
+		override = drm_edid_duplicate((const struct edid *)
+					      connector->edid_blob_ptr->data);
+
+	if (!override)
+		override = drm_load_edid_firmware(connector);
+
+	if (!IS_ERR_OR_NULL(override))
+		return override;
 
 	if ((edid = kmalloc(EDID_LENGTH, GFP_KERNEL)) == NULL)
 		return NULL;