hid: hid-picolcd: Remove struct backlight_ops.check_fb

Update the driver to initialize struct fb_info.bl_dev to its backlight
device, if any. Thus rely on the backlight core code to match backlight
and framebuffer devices, and remove the extra check_fb function from
struct backlight_ops.

v2:
	* protect against CONFIG_FB_BACKLIGHT (Javier, kernel test robot)
	* reword commit message (Daniel)
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Bruno Prémont <bonbons@linux-vserver.org>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://lore.kernel.org/r/20240305162425.23845-5-tzimmermann@suse.deSigned-off-by: Lee Jones <lee@kernel.org>

drivers/hid/hid-picolcd_backlight.c

@@ -9,7 +9,6 @@
 
 #include <linux/hid.h>
 
-#include <linux/fb.h>
 #include <linux/backlight.h>
 
 #include "hid-picolcd.h"
@@ -39,15 +38,9 @@ static int picolcd_set_brightness(struct backlight_device *bdev)
 	return 0;
 }
 
-static int picolcd_check_bl_fb(struct backlight_device *bdev, struct fb_info *fb)
-{
-	return fb && fb == picolcd_fbinfo((struct picolcd_data *)bl_get_data(bdev));
-}
-
 static const struct backlight_ops picolcd_blops = {
 	.update_status  = picolcd_set_brightness,
 	.get_brightness = picolcd_get_brightness,
-	.check_fb       = picolcd_check_bl_fb,
 };
 
 int picolcd_init_backlight(struct picolcd_data *data, struct hid_report *report)

drivers/hid/hid-picolcd_fb.c

@@ -493,6 +493,12 @@ int picolcd_init_framebuffer(struct picolcd_data *data)
 	info->fix = picolcdfb_fix;
 	info->fix.smem_len   = PICOLCDFB_SIZE*8;
 
+#ifdef CONFIG_FB_BACKLIGHT
+#ifdef CONFIG_HID_PICOLCD_BACKLIGHT
+	info->bl_dev = data->backlight;
+#endif
+#endif
+
 	fbdata = info->par;
 	spin_lock_init(&fbdata->lock);
 	fbdata->picolcd = data;