video: fbdev: core: Fix kernel-doc warnings in fbmon + fb_notify

Fix kernel-doc warnings reported when using W=1

v2:
  - Improve subject (Lee)

v3:
  - Add RETURNS documentation (Thomas)

v4:
  - Use Return: not RETURNS (Randy)
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Lee Jones <lee.jones@linaro.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: "Alexander A. Klimov" <grandmaster@al2klimov.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20201206205132.GA1869030@ravnborg.org

drivers/video/fbdev/core/fb_notify.c

@@ -19,6 +19,8 @@ static BLOCKING_NOTIFIER_HEAD(fb_notifier_list);
 /**
  *	fb_register_client - register a client notifier
  *	@nb: notifier block to callback on events
+ *
+ *	Return: 0 on success, negative error code on failure.
  */
 int fb_register_client(struct notifier_block *nb)
 {
@@ -29,6 +31,8 @@ EXPORT_SYMBOL(fb_register_client);
 /**
  *	fb_unregister_client - unregister a client notifier
  *	@nb: notifier block to callback on events
+ *
+ *	Return: 0 on success, negative error code on failure.
  */
 int fb_unregister_client(struct notifier_block *nb)
 {
@@ -38,7 +42,10 @@ EXPORT_SYMBOL(fb_unregister_client);
 
 /**
  * fb_notifier_call_chain - notify clients of fb_events
+ * @val: value passed to callback
+ * @v: pointer passed to callback
  *
+ * Return: The return value of the last notifier function
  */
 int fb_notifier_call_chain(unsigned long val, void *v)
 {

drivers/video/fbdev/core/fbmon.c

@@ -605,6 +605,7 @@ static void get_detailed_timing(unsigned char *block,
  * fb_create_modedb - create video mode database
  * @edid: EDID data
  * @dbsize: database size
+ * @specs: monitor specifications, may be NULL
  *
  * RETURNS: struct fb_videomode, @dbsize contains length of database
  *
@@ -1100,7 +1101,6 @@ static u32 fb_get_hblank_by_hfreq(u32 hfreq, u32 xres)
  *                                    2 * M
  *        M = 300;
  *        C = 30;
-
  */
 static u32 fb_get_hblank_by_dclk(u32 dclk, u32 xres)
 {