drm/edid: abstract debugfs override EDID set/reset

Add functions drm_edid_override_set() and drm_edid_override_reset() to
support "edid_override" connector debugfs, and to hide the details about
it in drm_edid.c. No functional changes at this time.

Also note in the connector.override_edid flag kernel-doc that this is
only supposed to be modified by the code doing debugfs EDID override
handling. Currently, it is still being modified by amdgpu in
create_eml_sink() and handle_edid_mgmt() for reasons unknown. This was
added in commit 4562236b3bc0 ("drm/amd/dc: Add dc display driver (v2)")
and later moved to amdgpu_dm.c in commit e7b07ceef2a6 ("drm/amd/display:
Merge amdgpu_dm_types and amdgpu_dm").

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/8f6b4001630cafac5f44aa5913429ac9979743d2.1656494768.git.jani.nikula@intel.com

drivers/gpu/drm/drm_crtc_internal.h

@@ -286,3 +286,5 @@ int drm_mode_page_flip_ioctl(struct drm_device *dev,
 
 /* drm_edid.c */
 void drm_mode_fixup_1366x768(struct drm_display_mode *mode);
+int drm_edid_override_set(struct drm_connector *connector, const void *edid, size_t size);
+int drm_edid_override_reset(struct drm_connector *connector);

drivers/gpu/drm/drm_debugfs.c

@@ -350,31 +350,20 @@ static ssize_t edid_write(struct file *file, const char __user *ubuf,
 	struct seq_file *m = file->private_data;
 	struct drm_connector *connector = m->private;
 	char *buf;
-	struct edid *edid;
 	int ret;
 
 	buf = memdup_user(ubuf, len);
 	if (IS_ERR(buf))
 		return PTR_ERR(buf);
 
-	edid = (struct edid *) buf;
+	if (len == 5 && !strncmp(buf, "reset", 5))
-
+		ret = drm_edid_override_reset(connector);
-	if (len == 5 && !strncmp(buf, "reset", 5)) {
+	else
-		connector->override_edid = false;
+		ret = drm_edid_override_set(connector, buf, len);
-		ret = drm_connector_update_edid_property(connector, NULL);
-	} else if (len < EDID_LENGTH ||
-		   EDID_LENGTH * (1 + edid->extensions) > len)
-		ret = -EINVAL;
-	else {
-		connector->override_edid = false;
-		ret = drm_connector_update_edid_property(connector, edid);
-		if (!ret)
-			connector->override_edid = true;
-	}
 
 	kfree(buf);
 
-	return (ret) ? ret : len;
+	return ret ? ret : len;
 }
 
 /*

drivers/gpu/drm/drm_edid.c

@@ -2161,6 +2161,32 @@ static struct edid *drm_get_override_edid(struct drm_connector *connector,
 	return IS_ERR(override) ? NULL : override;
 }
 
+/* For debugfs edid_override implementation */
+int drm_edid_override_set(struct drm_connector *connector, const void *edid,
+			  size_t size)
+{
+	int ret;
+
+	if (size < EDID_LENGTH || edid_size(edid) > size)
+		return -EINVAL;
+
+	connector->override_edid = false;
+
+	ret = drm_connector_update_edid_property(connector, edid);
+	if (!ret)
+		connector->override_edid = true;
+
+	return ret;
+}
+
+/* For debugfs edid_override implementation */
+int drm_edid_override_reset(struct drm_connector *connector)
+{
+	connector->override_edid = false;
+
+	return drm_connector_update_edid_property(connector, NULL);
+}
+
 /**
  * drm_add_override_edid_modes - add modes from override/firmware EDID
  * @connector: connector we're probing

include/drm/drm_connector.h

@@ -1527,7 +1527,11 @@ struct drm_connector {
 	struct drm_cmdline_mode cmdline_mode;
 	/** @force: a DRM_FORCE_<foo> state for forced mode sets */
 	enum drm_connector_force force;
-	/** @override_edid: has the EDID been overwritten through debugfs for testing? */
+	/**
+	 * @override_edid: has the EDID been overwritten through debugfs for
+	 * testing? Do not modify outside of drm_edid_override_set() and
+	 * drm_edid_override_reset().
+	 */
 	bool override_edid;
 	/** @epoch_counter: used to detect any other changes in connector, besides status */
 	u64 epoch_counter;