sysfs: simplify attribute definition macros

Define the macros in terms of each other.
This makes them easier to understand and also will make it easier to
implement the transition machinery for 'const struct attribute'.

__ATTR_RO_MODE() can't be implemented in terms of __ATTR() as not all
attributes have a .store callback. The same issue theoretically exists
for __ATTR_WO(), but practically that does not occur today.

Reorder __ATTR_RO() below __ATTR_RO_MODE() to keep the order of the
macro definition consistent with respect to each other.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Link: https://patch.msgid.link/20251029-sysfs-const-attr-prep-v5-7-ea7d745acff4@weissschuh.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: t-8ch

include/linux/sysfs.h

@@ -251,28 +251,20 @@ struct attribute_group {
 	.store	= _store,						\
 }
 
-#define __ATTR_RO(_name) {						\
-	.attr	= { .name = __stringify(_name), .mode = 0444 },		\
-	.show	= _name##_show,						\
-}
-
 #define __ATTR_RO_MODE(_name, _mode) {					\
 	.attr	= { .name = __stringify(_name),				\
 		    .mode = VERIFY_OCTAL_PERMISSIONS(_mode) },		\
 	.show	= _name##_show,						\
 }
 
-#define __ATTR_RW_MODE(_name, _mode) {					\
-	.attr	= { .name = __stringify(_name),				\
-		    .mode = VERIFY_OCTAL_PERMISSIONS(_mode) },		\
-	.show	= _name##_show,						\
-	.store	= _name##_store,					\
-}
+#define __ATTR_RO(_name)						\
+	__ATTR_RO_MODE(_name, 0444)
 
-#define __ATTR_WO(_name) {						\
-	.attr	= { .name = __stringify(_name), .mode = 0200 },		\
-	.store	= _name##_store,					\
-}
+#define __ATTR_RW_MODE(_name, _mode)					\
+	__ATTR(_name, _mode, _name##_show, _name##_store)
+
+#define __ATTR_WO(_name)						\
+	__ATTR(_name, 0200, NULL, _name##_store)
 
 #define __ATTR_RW(_name) __ATTR(_name, 0644, _name##_show, _name##_store)