drm/selftests: reduce stack usage

Putting a large drm_connector object on the stack can lead to warnings
in some configuration, such as:

drivers/gpu/drm/selftests/test-drm_cmdline_parser.c:18:12: error: stack frame size of 1040 bytes in function 'drm_cmdline_test_res' [-Werror,-Wframe-larger-than=]
static int drm_cmdline_test_res(void *ignored)

Since the object is never modified, just declare it as 'static const'
and allow this to be passed down.

Fixes: b7ced389 ("drm/selftests: Add command line parser selftests")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190628121712.1928142-1-arnd@arndb.de

drivers/gpu/drm/drm_modes.c

@@ -1448,7 +1448,7 @@ static int drm_mode_parse_cmdline_refresh(const char *str, char **end_ptr,
 }
 
 static int drm_mode_parse_cmdline_extra(const char *str, int length,
-					struct drm_connector *connector,
+					const struct drm_connector *connector,
 					struct drm_cmdline_mode *mode)
 {
 	int i;
@@ -1493,7 +1493,7 @@ static int drm_mode_parse_cmdline_extra(const char *str, int length,
 
 static int drm_mode_parse_cmdline_res_mode(const char *str, unsigned int length,
 					   bool extras,
-					   struct drm_connector *connector,
+					   const struct drm_connector *connector,
 					   struct drm_cmdline_mode *mode)
 {
 	const char *str_start = str;
@@ -1555,7 +1555,7 @@ static int drm_mode_parse_cmdline_res_mode(const char *str, unsigned int length,
 }
 
 static int drm_mode_parse_cmdline_options(char *str, size_t len,
-					  struct drm_connector *connector,
+					  const struct drm_connector *connector,
 					  struct drm_cmdline_mode *mode)
 {
 	unsigned int rotation = 0;
@@ -1689,7 +1689,7 @@ static int drm_mode_parse_cmdline_options(char *str, size_t len,
  * True if a valid modeline has been parsed, false otherwise.
  */
 bool drm_mode_parse_command_line_for_connector(const char *mode_option,
-					       struct drm_connector *connector,
+					       const struct drm_connector *connector,
 					       struct drm_cmdline_mode *mode)
 {
 	const char *name;

include/drm/drm_modes.h

@@ -537,7 +537,7 @@ void drm_connector_list_update(struct drm_connector *connector);
 /* parsing cmdline modes */
 bool
 drm_mode_parse_command_line_for_connector(const char *mode_option,
-					  struct drm_connector *connector,
+					  const struct drm_connector *connector,
 					  struct drm_cmdline_mode *mode);
 struct drm_display_mode *
 drm_mode_create_from_cmdline_mode(struct drm_device *dev,