fbdev: Send old blank state in FB_EVENT_BLANK

The event FB_EVENT_BLANK sends the new blank state in the event's
data field. Also send the old state. It's an additional field in the
data array; existing receivers won't notice the difference.

The backlight subsystem currently tracks blank state per display per
backlight. That is not optimal as it ties backlight code to fbdev. A
subsystem should not track internal state of another subsystem. With
both, new and old, blank state in FB_EVENT_BLANK, the backlight code
will not require its own state tracker any longer.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Simona Vetter <simona.vetter@ffwll.ch>
Link: https://lore.kernel.org/r/20250321095517.313713-4-tzimmermann@suse.de
Signed-off-by: Lee Jones <lee@kernel.org>

Author: Thomas Zimmermann

drivers/video/fbdev/core/fbmem.c

@@ -343,6 +343,7 @@ int fb_blank(struct fb_info *info, int blank)
 {
 	int old_blank = info->blank;
 	struct fb_event event;
+	int data[2];
 	int ret;
 
 	if (!info->fbops->fb_blank)
@@ -351,8 +352,10 @@ int fb_blank(struct fb_info *info, int blank)
 	if (blank > FB_BLANK_POWERDOWN)
 		blank = FB_BLANK_POWERDOWN;
 
+	data[0] = blank;
+	data[1] = old_blank;
 	event.info = info;
-	event.data = ␣
+	event.data = data;
 
 	info->blank = blank;