From 840fe258332544aa7321921e1723d37b772af7a9 Mon Sep 17 00:00:00 2001
From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: Tue, 19 Oct 2021 16:45:09 +0200
Subject: [PATCH] auxdisplay: ht16k33: Fix frame buffer device blanking
Git-commit: 840fe258332544aa7321921e1723d37b772af7a9
Patch-mainline: v5.16-rc1
References: git-fixes stable-5.14.19

As the ht16k33 frame buffer sub-driver does not register an
fb_ops.fb_blank() handler, blanking does not work:

    $ echo 1 > /sys/class/graphics/fb0/blank
    sh: write error: Invalid argument

Fix this by providing a handler that always returns zero, to make sure
blank events will be sent to the actual device handling the backlight.

Reported-by: Robin van der Gracht <robin@protonic.nl>
Suggested-by: Robin van der Gracht <robin@protonic.nl>
Fixes: 8992da44c6805d53 ("auxdisplay: ht16k33: Driver for LED controller")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/auxdisplay/ht16k33.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/auxdisplay/ht16k33.c b/drivers/auxdisplay/ht16k33.c
index 2b630e194570..ed5808349990 100644
--- a/drivers/auxdisplay/ht16k33.c
+++ b/drivers/auxdisplay/ht16k33.c
@@ -219,6 +219,15 @@ static const struct backlight_ops ht16k33_bl_ops = {
 	.check_fb	= ht16k33_bl_check_fb,
 };
 
+/*
+ * Blank events will be passed to the actual device handling the backlight when
+ * we return zero here.
+ */
+static int ht16k33_blank(int blank, struct fb_info *info)
+{
+	return 0;
+}
+
 static int ht16k33_mmap(struct fb_info *info, struct vm_area_struct *vma)
 {
 	struct ht16k33_priv *priv = info->par;
@@ -231,6 +240,7 @@ static const struct fb_ops ht16k33_fb_ops = {
 	.owner = THIS_MODULE,
 	.fb_read = fb_sys_read,
 	.fb_write = fb_sys_write,
+	.fb_blank = ht16k33_blank,
 	.fb_fillrect = sys_fillrect,
 	.fb_copyarea = sys_copyarea,
 	.fb_imageblit = sys_imageblit,
-- 
2.26.2