firmware: dmi_scan: Add DMI_OEM_STRING support to dmi_matches

OEM strings are defined by each OEM and they contain customized and
useful OEM information. Supporting it provides more flexible uses of
the dmi_matches function.
Signed-off-by: Alex Hung <alex.hung@canonical.com>
Signed-off-by: Jean Delvare <jdelvare@suse.de>

drivers/firmware/dmi_scan.c

@@ -775,7 +775,15 @@ static bool dmi_matches(const struct dmi_system_id *dmi)
 		int s = dmi->matches[i].slot;
 		if (s == DMI_NONE)
 			break;
-		if (dmi_ident[s]) {
+		if (s == DMI_OEM_STRING) {
+			/* DMI_OEM_STRING must be exact match */
+			const struct dmi_device *valid;
+
+			valid = dmi_find_device(DMI_DEV_TYPE_OEM_STRING,
+						dmi->matches[i].substr, NULL);
+			if (valid)
+				continue;
+		} else if (dmi_ident[s]) {
 			if (dmi->matches[i].exact_match) {
 				if (!strcmp(dmi_ident[s],
 					    dmi->matches[i].substr))

include/linux/mod_devicetable.h

@@ -502,6 +502,7 @@ enum dmi_field {
 	DMI_CHASSIS_SERIAL,
 	DMI_CHASSIS_ASSET_TAG,
 	DMI_STRING_MAX,
+	DMI_OEM_STRING,	/* special case - will not be in dmi_ident */
 };
 
 struct dmi_strmatch {