drm/xe/configfs: Fix engine class parsing

If mask is NULL, only the engine class should be accepted, so the
pattern string should be completely parsed. This should fix passing e.g.
rcs0 to ctx_restore_post_bb when it's only expecting the engine class.

Reported-by: Jonathan Cavitt <[email protected]>
Closes: https://lore.kernel.org/r/[email protected]
Reported-by: Dan Carpenter <[email protected]>
Closes: https://lore.kernel.org/r/[email protected]
Fixes: e2a9854 ("drm/xe/configfs: Allow to select by class only")
Reviewed-by: Jonathan Cavitt <[email protected]>
Reviewed-by: Raag Jadav <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Lucas De Marchi <[email protected]>
(cherry picked from commit dd79796)
Signed-off-by: Lucas De Marchi <[email protected]>

Author: Lucas De Marchi

drivers/gpu/drm/xe/xe_configfs.c

@@ -324,8 +324,8 @@ static const struct engine_info *lookup_engine_info(const char *pattern, u64 *ma
 			continue;
 
 		pattern += strlen(engine_info[i].cls);
-		if (!mask && !*pattern)
-			return &engine_info[i];
+		if (!mask)
+			return *pattern ? NULL : &engine_info[i];
 
 		if (!strcmp(pattern, "*")) {
 			*mask = engine_info[i].mask;