drm/edid: Add a function to match EDID with identity

Create a type drm_edid_ident as the identity of an EDID. Currently it
contains panel id and monitor name.

Create a function that can match a given EDID and an identity:
1. Reject if the panel id doesn't match.
2. If name is not null in identity, try to match it in the detailed timing
   blocks. Note that some panel vendors put the monitor name after
   EDID_DETAIL_MONITOR_STRING.
Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240307230653.1807557-3-hsinyi@chromium.org

drivers/gpu/drm/drm_edid.c

@@ -102,6 +102,11 @@ struct detailed_mode_closure {
 	int modes;
 };
 
+struct drm_edid_match_closure {
+	const struct drm_edid_ident *ident;
+	bool matched;
+};
+
 #define LEVEL_DMT	0
 #define LEVEL_GTF	1
 #define LEVEL_GTF2	2
@@ -5455,6 +5460,66 @@ drm_parse_hdmi_vsdb_audio(struct drm_connector *connector, const u8 *db)
 		    connector->audio_latency[0], connector->audio_latency[1]);
 }
 
+static void
+match_identity(const struct detailed_timing *timing, void *data)
+{
+	struct drm_edid_match_closure *closure = data;
+	unsigned int i;
+	const char *name = closure->ident->name;
+	unsigned int name_len = strlen(name);
+	const char *desc = timing->data.other_data.data.str.str;
+	unsigned int desc_len = ARRAY_SIZE(timing->data.other_data.data.str.str);
+
+	if (name_len > desc_len ||
+	    !(is_display_descriptor(timing, EDID_DETAIL_MONITOR_NAME) ||
+	      is_display_descriptor(timing, EDID_DETAIL_MONITOR_STRING)))
+		return;
+
+	if (strncmp(name, desc, name_len))
+		return;
+
+	for (i = name_len; i < desc_len; i++) {
+		if (desc[i] == '\n')
+			break;
+		/* Allow white space before EDID string terminator. */
+		if (!isspace(desc[i]))
+			return;
+	}
+
+	closure->matched = true;
+}
+
+/**
+ * drm_edid_match - match drm_edid with given identity
+ * @drm_edid: EDID
+ * @ident: the EDID identity to match with
+ *
+ * Check if the EDID matches with the given identity.
+ *
+ * Return: True if the given identity matched with EDID, false otherwise.
+ */
+bool drm_edid_match(const struct drm_edid *drm_edid,
+		    const struct drm_edid_ident *ident)
+{
+	if (!drm_edid || drm_edid_get_panel_id(drm_edid) != ident->panel_id)
+		return false;
+
+	/* Match with name only if it's not NULL. */
+	if (ident->name) {
+		struct drm_edid_match_closure closure = {
+			.ident = ident,
+			.matched = false,
+		};
+
+		drm_for_each_detailed_block(drm_edid, match_identity, &closure);
+
+		return closure.matched;
+	}
+
+	return true;
+}
+EXPORT_SYMBOL(drm_edid_match);
+
 static void
 monitor_name(const struct detailed_timing *timing, void *data)
 {

include/drm/drm_edid.h

@@ -312,6 +312,13 @@ struct edid {
 	u8 checksum;
 } __packed;
 
+/* EDID matching */
+struct drm_edid_ident {
+	/* ID encoded by drm_edid_encode_panel_id() */
+	u32 panel_id;
+	const char *name;
+};
+
 #define EDID_PRODUCT_ID(e) ((e)->prod_code[0] | ((e)->prod_code[1] << 8))
 
 /* Short Audio Descriptor */
@@ -412,6 +419,8 @@ struct edid *drm_get_edid(struct drm_connector *connector,
 			  struct i2c_adapter *adapter);
 const struct drm_edid *drm_edid_read_base_block(struct i2c_adapter *adapter);
 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);
 struct edid *drm_get_edid_switcheroo(struct drm_connector *connector,
 				     struct i2c_adapter *adapter);
 struct edid *drm_edid_duplicate(const struct edid *edid);