linux-kernel - [PATCH v7 10/21] auxdisplay: ht16k33: Fix frame buffer device blanking

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Date:   Tue, 12 Oct 2021 20:33:16 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Miguel Ojeda <ojeda@...nel.org>
Cc:     Robin van der Gracht <robin@...tonic.nl>,
        Rob Herring <robh+dt@...nel.org>,
        Paul Burton <paulburton@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Pavel Machek <pavel@....cz>, Marek Behun <marek.behun@....cz>,
        devicetree@...r.kernel.org, linux-leds@...r.kernel.org,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: [PATCH v7 10/21] auxdisplay: ht16k33: Fix frame buffer device blanking

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@...tonic.nl>
Suggested-by: Robin van der Gracht <robin@...tonic.nl>
Fixes: 8992da44c6805d53 ("auxdisplay: ht16k33: Driver for LED controller")
Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
---
v7:
  - New.
---
 drivers/auxdisplay/ht16k33.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/auxdisplay/ht16k33.c b/drivers/auxdisplay/ht16k33.c
index 2b630e194570f6e5..ed5808349990782c 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,
-- 
2.25.1