DMI: allow omitting ident strings in DMI tables

The purpose of dmi->ident is twofold - it may be used by DMI callback
functions when composing log messages; it is also used to determine
end of DMI table in dmi_check_system() and dmi_first_match(). However,
in case when callbacks are not interested in using ident at all it just
wastes memory. Let's make entries with empty first match slot serve as
end-of-table markers instead.
Acked-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

drivers/firmware/dmi_scan.c

@@ -429,7 +429,7 @@ static bool dmi_matches(const struct dmi_system_id *dmi)
 	for (i = 0; i < ARRAY_SIZE(dmi->matches); i++) {
 		int s = dmi->matches[i].slot;
 		if (s == DMI_NONE)
-			continue;
+			break;
 		if (dmi_ident[s]
 		    && strstr(dmi_ident[s], dmi->matches[i].substr))
 			continue;
@@ -439,6 +439,15 @@ static bool dmi_matches(const struct dmi_system_id *dmi)
 	return true;
 }
 
+/**
+ *	dmi_is_end_of_table - check for end-of-table marker
+ *	@dmi: pointer to the dmi_system_id structure to check
+ */
+static bool dmi_is_end_of_table(const struct dmi_system_id *dmi)
+{
+	return dmi->matches[0].slot == DMI_NONE;
+}
+
 /**
  *	dmi_check_system - check system DMI data
  *	@list: array of dmi_system_id structures to match against
@@ -457,7 +466,7 @@ int dmi_check_system(const struct dmi_system_id *list)
 	int count = 0;
 	const struct dmi_system_id *d;
 
-	for (d = list; d->ident; d++)
+	for (d = list; !dmi_is_end_of_table(d); d++)
 		if (dmi_matches(d)) {
 			count++;
 			if (d->callback && d->callback(d))
@@ -484,7 +493,7 @@ const struct dmi_system_id *dmi_first_match(const struct dmi_system_id *list)
 {
 	const struct dmi_system_id *d;
 
-	for (d = list; d->ident; d++)
+	for (d = list; !dmi_is_end_of_table(d); d++)
 		if (dmi_matches(d))
 			return d;