backlight: lcd: Replace fb events with a dedicated function call

Remove support for fb events from the lcd subsystem. Provide the
helper lcd_notify_blank_all() instead. In fbdev, call
lcd_notify_blank_all() to inform the lcd subsystem of changes
to a display's blank state.

Fbdev maintains a list of all installed notifiers. Instead of fbdev
notifiers, maintain an internal list of lcd devices.

v3:
- export lcd_notify_mode_change_all() (kernel test robot)
v2:
- maintain global list of lcd devices
- avoid IS_REACHABLE() in source file
- use lock guards
- initialize lcd list and list mutex

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Simona Vetter <simona.vetter@ffwll.ch>
Reviewed-by: "Daniel Thompson (RISCstar)" <danielt@kernel.org>
Link: https://lore.kernel.org/r/20250321095517.313713-9-tzimmermann@suse.de
Signed-off-by: Lee Jones <lee@kernel.org>

1 files changed, 35 insertions, 4 deletions

diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
index c931f270ac34..001662c606d7 100644
--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c
@@ -15,6 +15,7 @@
 #include <linux/export.h>
 #include <linux/fb.h>
 #include <linux/fbcon.h>
+#include <linux/lcd.h>
 
 #include <video/nomodeset.h>
 
@@ -220,6 +221,12 @@ static int fb_check_caps(struct fb_info *info, struct fb_var_screeninfo *var,
 	return err;
 }
 
+static void fb_lcd_notify_mode_change(struct fb_info *info,
+				      struct fb_videomode *mode)
+{
+	lcd_notify_mode_change_all(info->device, mode->xres, mode->yres);
+}
+
 int
 fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var)
 {
@@ -227,7 +234,6 @@ fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var)
 	u32 activate;
 	struct fb_var_screeninfo old_var;
 	struct fb_videomode mode;
-	struct fb_event event;
 	u32 unused;
 
 	if (var->activate & FB_ACTIVATE_INV_MODE) {
@@ -331,14 +337,38 @@ fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var)
 	if (ret)
 		return ret;
 
-	event.info = info;
-	event.data = &mode;
-	fb_notifier_call_chain(FB_EVENT_MODE_CHANGE, &event);
+	fb_lcd_notify_mode_change(info, &mode);
 
 	return 0;
 }
 EXPORT_SYMBOL(fb_set_var);
 
+static void fb_lcd_notify_blank(struct fb_info *info)
+{
+	int power;
+
+	switch (info->blank) {
+	case FB_BLANK_UNBLANK:
+		power = LCD_POWER_ON;
+		break;
+	/* deprecated; TODO: should become 'off' */
+	case FB_BLANK_NORMAL:
+		power = LCD_POWER_REDUCED;
+		break;
+	case FB_BLANK_VSYNC_SUSPEND:
+		power = LCD_POWER_REDUCED_VSYNC_SUSPEND;
+		break;
+	/* 'off' */
+	case FB_BLANK_HSYNC_SUSPEND:
+	case FB_BLANK_POWERDOWN:
+	default:
+		power = LCD_POWER_OFF;
+		break;
+	}
+
+	lcd_notify_blank_all(info->device, power);
+}
+
 int fb_blank(struct fb_info *info, int blank)
 {
 	int old_blank = info->blank;
@@ -364,6 +394,7 @@ int fb_blank(struct fb_info *info, int blank)
 		goto err;
 
 	fb_bl_notify_blank(info, old_blank);
+	fb_lcd_notify_blank(info);
 
 	fb_notifier_call_chain(FB_EVENT_BLANK, &event);