[PATCH] drm: Update edid-derived drm_display_info fields at edid property set [v2]

Keith Packard keithp at keithp.com
Wed Dec 13 08:44:26 UTC 2017

There are a set of values in the drm_display_info structure for each
connector which hold information derived from EDID. These are computed
in drm_add_display_info. Before this patch, that was only called in
drm_add_edid_modes. This meant that they were only set when EDID was
present and never reset when EDID was not, as happened when the
display was disconnected.

One of these fields, non_desktop, is used from
drm_mode_connector_update_edid_property, the function responsible for
assigning the new edid value to the application-visible property.

Various drivers call these two functions (drm_add_edid_modes and
drm_mode_connector_update_edid_property) in different orders. This
means that even when EDID is present, the drm_display_info fields may
not have been computed at the time that
drm_mode_connector_update_edid_property used the non_desktop value to
set the non_desktop property.

I've added a public function (drm_reset_display_info) that resets the
drm_display_info field values to default values and then made the
drm_add_display_info function public. These two functions are now
called directly from drm_mode_connector_update_edid_property so that
the drm_display_info fields are always computed from the current EDID
information before being used in that function.

This means that the drm_display_info values are often computed twice,
once when the EDID property it set and a second time when EDID is used
to compute modes for the device. The alternative would be to uniformly
ensure that the values were computed once before being used, which
would require that all drivers reliably invoke the two paths in the
same order. The computation is inexpensive enough that it seems more
maintainable in the long term to simply compute them in both paths.

The API to drm_add_display_info has been changed so that it no longer
takes the set of edid-based quirks as a parameter. Rather, it now
computes those quirks itself and returns them for further use by

This patch also includes a number of 'const' additions caused by
drm_mode_connector_update_edid_property taking a 'const struct edid *'
parameter and wanting to pass that along to drm_add_display_info.

v2: after review by Daniel Vetter <daniel.vetter at ffwll.ch>

	Removed EXPORT_SYMBOL_GPL for drm_reset_display_info and

	Added FIXME in drm_mode_connector_update_edid_property about
	potentially merging that with drm_add_edid_modes to avoid
	the need for two driver calls.

Signed-off-by: Keith Packard <keithp at keithp.com>
Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
 drivers/gpu/drm/drm_connector.c | 13 ++++++++++
 drivers/gpu/drm/drm_edid.c      | 53 ++++++++++++++++++++++++++++++-----------
 include/drm/drm_edid.h          |  2 ++
 3 files changed, 54 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
index 25f4b2e9a44f..83c01f359d55 100644
--- a/drivers/gpu/drm/drm_connector.c
+++ b/drivers/gpu/drm/drm_connector.c
@@ -1207,6 +1207,19 @@ int drm_mode_connector_update_edid_property(struct drm_connector *connector,
 	if (edid)
 		size = EDID_LENGTH * (1 + edid->extensions);
+	/* Set the display info, using edid if available, otherwise
+	 * reseting the values to defaults. This duplicates the work
+	 * done in drm_add_edid_modes, but that function is not
+	 * consistently called before this one in all drivers and the
+	 * computation is cheap enough that it seems better to
+	 * duplicate it rather than attempt to ensure some arbitrary
+	 * ordering of calls.
+	 */
+	if (edid)
+		drm_add_display_info(connector, edid);
+	else
+		drm_reset_display_info(connector);
diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 524eace3d460..365901c1c33c 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -1731,7 +1731,7 @@ EXPORT_SYMBOL(drm_edid_duplicate);
  * Returns true if @vendor is in @edid, false otherwise
-static bool edid_vendor(struct edid *edid, const char *vendor)
+static bool edid_vendor(const struct edid *edid, const char *vendor)
 	char edid_vendor[3];
@@ -1749,7 +1749,7 @@ static bool edid_vendor(struct edid *edid, const char *vendor)
  * This tells subsequent routines what fixes they need to apply.
-static u32 edid_get_quirks(struct edid *edid)
+static u32 edid_get_quirks(const struct edid *edid)
 	const struct edid_quirk *quirk;
 	int i;
@@ -2813,7 +2813,7 @@ add_detailed_modes(struct drm_connector *connector, struct edid *edid,
  * Search EDID for CEA extension block.
-static u8 *drm_find_edid_extension(struct edid *edid, int ext_id)
+static u8 *drm_find_edid_extension(const struct edid *edid, int ext_id)
 	u8 *edid_ext = NULL;
 	int i;
@@ -2835,12 +2835,12 @@ static u8 *drm_find_edid_extension(struct edid *edid, int ext_id)
 	return edid_ext;
-static u8 *drm_find_cea_extension(struct edid *edid)
+static u8 *drm_find_cea_extension(const struct edid *edid)
 	return drm_find_edid_extension(edid, CEA_EXT);
-static u8 *drm_find_displayid_extension(struct edid *edid)
+static u8 *drm_find_displayid_extension(const struct edid *edid)
 	return drm_find_edid_extension(edid, DISPLAYID_EXT);
@@ -4378,7 +4378,7 @@ drm_parse_hdmi_vsdb_video(struct drm_connector *connector, const u8 *db)
 static void drm_parse_cea_ext(struct drm_connector *connector,
-			      struct edid *edid)
+			      const struct edid *edid)
 	struct drm_display_info *info = &connector->display_info;
 	const u8 *edid_ext;
@@ -4412,11 +4412,34 @@ static void drm_parse_cea_ext(struct drm_connector *connector,
-static void drm_add_display_info(struct drm_connector *connector,
-				 struct edid *edid, u32 quirks)
+/* A connector has no EDID information, so we've got no EDID to compute quirks from. Reset
+ * all of the values which would have been set from EDID
+ */
+drm_reset_display_info(struct drm_connector *connector)
+	struct drm_display_info *info = &connector->display_info;
+	info->width_mm = 0;
+	info->height_mm = 0;
+	info->bpc = 0;
+	info->color_formats = 0;
+	info->cea_rev = 0;
+	info->max_tmds_clock = 0;
+	info->dvi_dual = false;
+	info->has_hdmi_infoframe = false;
+	info->non_desktop = 0;
+u32 drm_add_display_info(struct drm_connector *connector, const struct edid *edid)
 	struct drm_display_info *info = &connector->display_info;
+	u32 quirks = edid_get_quirks(edid);
 	info->width_mm = edid->width_cm * 10;
 	info->height_mm = edid->height_cm * 10;
@@ -4430,11 +4453,13 @@ static void drm_add_display_info(struct drm_connector *connector,
 	info->non_desktop = !!(quirks & EDID_QUIRK_NON_DESKTOP);
+	DRM_DEBUG_KMS("non_desktop set to %d\n", info->non_desktop);
 	if (edid->revision < 3)
-		return;
+		return quirks;
 	if (!(edid->input & DRM_EDID_INPUT_DIGITAL))
-		return;
+		return quirks;
 	drm_parse_cea_ext(connector, edid);
@@ -4454,7 +4479,7 @@ static void drm_add_display_info(struct drm_connector *connector,
 	/* Only defined for 1.4 with digital displays */
 	if (edid->revision < 4)
-		return;
+		return quirks;
 	switch (edid->input & DRM_EDID_DIGITAL_DEPTH_MASK) {
@@ -4489,7 +4514,9 @@ static void drm_add_display_info(struct drm_connector *connector,
 		info->color_formats |= DRM_COLOR_FORMAT_YCRCB444;
 	if (edid->features & DRM_EDID_FEATURE_RGB_YCRCB422)
 		info->color_formats |= DRM_COLOR_FORMAT_YCRCB422;
+	return quirks;
 static int validate_displayid(u8 *displayid, int length, int idx)
@@ -4645,8 +4672,6 @@ int drm_add_edid_modes(struct drm_connector *connector, struct edid *edid)
 		return 0;
-	quirks = edid_get_quirks(edid);
 	drm_edid_to_eld(connector, edid);
@@ -4654,7 +4679,7 @@ int drm_add_edid_modes(struct drm_connector *connector, struct edid *edid)
 	 * To avoid multiple parsing of same block, lets parse that map
 	 * from sink info, before parsing CEA modes.
-	drm_add_display_info(connector, edid, quirks);
+	quirks = drm_add_display_info(connector, edid);
 	 * EDID spec says modes should be preferred in this order:
diff --git a/include/drm/drm_edid.h b/include/drm/drm_edid.h
index b25d12ef120a..8d89a9c3748d 100644
--- a/include/drm/drm_edid.h
+++ b/include/drm/drm_edid.h
@@ -465,6 +465,8 @@ struct edid *drm_get_edid(struct drm_connector *connector,
 struct edid *drm_get_edid_switcheroo(struct drm_connector *connector,
 				     struct i2c_adapter *adapter);
 struct edid *drm_edid_duplicate(const struct edid *edid);
+void drm_reset_display_info(struct drm_connector *connector);
+u32 drm_add_display_info(struct drm_connector *connector, const struct edid *edid);
 int drm_add_edid_modes(struct drm_connector *connector, struct edid *edid);
 u8 drm_match_cea_mode(const struct drm_display_mode *to_match);

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