FAILED: patch "[PATCH] auxdisplay: charlcd: cancel backlight work on registration" failed to apply to 5.10-stable tree

FAILED: patch "[PATCH] auxdisplay: charlcd: cancel backlight work on registration" failed to apply to 5.10-stable tree

[gregkh]

The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x e3e3bf40916c1e810df03958cfa7ba6883cdce79
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026090350-stencil-mud-1d68@gregkh' --subject-prefix 'PATCH 5.10.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From e3e3bf40916c1e810df03958cfa7ba6883cdce79 Mon Sep 17 00:00:00 2001
From: Hongyan Xu <getshell@seu.edu.cn>
Date: Sat, 15 Aug 2026 18:59:50 +0800
Subject: [PATCH] auxdisplay: charlcd: cancel backlight work on registration
 failure

With CONFIG_CHARLCD_BL_FLASH, charlcd_init() schedules bl_work before
charlcd_register() calls misc_register(). If registration fails, the
caller frees the charlcd object while delayed work still contains its
address.

Add charlcd_deinit() to cancel the delayed work and turn the backlight
off. Use it for both registration rollback and normal unregistration.

Fixes: 39f8ea46724e ("auxdisplay: charlcd: Extract character LCD core from misc/panel")
Cc: stable@vger.kernel.org
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Hongyan Xu <getshell@seu.edu.cn>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

diff --git a/drivers/auxdisplay/charlcd.c b/drivers/auxdisplay/charlcd.c
index 09020bb8ad15..ae2692ec3963 100644
--- a/drivers/auxdisplay/charlcd.c
+++ b/drivers/auxdisplay/charlcd.c
@@ -595,6 +595,16 @@ static int charlcd_init(struct charlcd *lcd)
 	return 0;
 }
 
+static void charlcd_deinit(struct charlcd *lcd)
+{
+	struct charlcd_priv *priv = charlcd_to_priv(lcd);
+
+	if (lcd->ops->backlight) {
+		cancel_delayed_work_sync(&priv->bl_work);
+		lcd->ops->backlight(lcd, CHARLCD_OFF);
+	}
+}
+
 struct charlcd *charlcd_alloc(unsigned int drvdata_size)
 {
 	struct charlcd_priv *priv;
@@ -654,8 +664,10 @@ int charlcd_register(struct charlcd *lcd)
 		return ret;
 
 	ret = misc_register(&charlcd_dev);
-	if (ret)
+	if (ret) {
+		charlcd_deinit(lcd);
 		return ret;
+	}
 
 	the_charlcd = lcd;
 	register_reboot_notifier(&panel_notifier);
@@ -665,16 +677,11 @@ EXPORT_SYMBOL_GPL(charlcd_register);
 
 int charlcd_unregister(struct charlcd *lcd)
 {
-	struct charlcd_priv *priv = charlcd_to_priv(lcd);
-
 	unregister_reboot_notifier(&panel_notifier);
 	charlcd_puts(lcd, "\x0cLCD driver unloaded.\x1b[Lc\x1b[Lb\x1b[L-");
 	misc_deregister(&charlcd_dev);
 	the_charlcd = NULL;
-	if (lcd->ops->backlight) {
-		cancel_delayed_work_sync(&priv->bl_work);
-		priv->lcd.ops->backlight(&priv->lcd, CHARLCD_OFF);
-	}
+	charlcd_deinit(lcd);
 
 	return 0;
 }

[PATCH 5.10.y 1/2] auxdisplay: Move init_display to hd44780_common

[Sasha Levin]

From: Lars Poeschel <poeschel@lemonage.de>

[ Upstream commit 01ec46dfa633a52ccfe38d4a194460d6adb2ba00 ]

The init_display function is moved over to hd44780_common. charlcd uses
it via its ops function pointer and drivers initialize the ops with the
common hd44780_common_init_display function.

Reviewed-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Lars Poeschel <poeschel@lemonage.de>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

[ stable 5.10: The hd44780_common infrastructure and the prerequisite
  refactoring series are not present. Drop the init_display move and carry
  only the charlcd backlight enum normalization needed by the follow-up fix. ]

[ sashal: Reduced backport -- upstream 01ec46dfa633a touches 6 file(s), this
  backport carries 2. Not backported here:
  drivers/auxdisplay/hd44780.c
  drivers/auxdisplay/hd44780_common.c
  drivers/auxdisplay/hd44780_common.h
  drivers/auxdisplay/panel.c
  This note is generated from the file lists only; see the resolution record
  for the reasoning. ]

Stable-dep-of: e3e3bf40916c ("auxdisplay: charlcd: cancel backlight work on registration failure")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/auxdisplay/charlcd.c | 6 +++---
 drivers/auxdisplay/charlcd.h | 5 +++++
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/auxdisplay/charlcd.c b/drivers/auxdisplay/charlcd.c
index 5aee0f5463514..e74e25ff030b2 100644
--- a/drivers/auxdisplay/charlcd.c
+++ b/drivers/auxdisplay/charlcd.c
@@ -124,7 +124,7 @@ static void charlcd_bl_off(struct work_struct *work)
 	if (priv->bl_tempo) {
 		priv->bl_tempo = false;
 		if (!(priv->flags & LCD_FLAG_L))
-			priv->lcd.ops->backlight(&priv->lcd, 0);
+			priv->lcd.ops->backlight(&priv->lcd, CHARLCD_OFF);
 	}
 	mutex_unlock(&priv->bl_tempo_lock);
 }
@@ -141,7 +141,7 @@ void charlcd_poke(struct charlcd *lcd)
 
 	mutex_lock(&priv->bl_tempo_lock);
 	if (!priv->bl_tempo && !(priv->flags & LCD_FLAG_L))
-		lcd->ops->backlight(lcd, 1);
+		lcd->ops->backlight(lcd, CHARLCD_ON);
 	priv->bl_tempo = true;
 	schedule_delayed_work(&priv->bl_work, LCD_BL_TEMPO_PERIOD * HZ);
 	mutex_unlock(&priv->bl_tempo_lock);
@@ -862,7 +862,7 @@ int charlcd_unregister(struct charlcd *lcd)
 	the_charlcd = NULL;
 	if (lcd->ops->backlight) {
 		cancel_delayed_work_sync(&priv->bl_work);
-		priv->lcd.ops->backlight(&priv->lcd, 0);
+		priv->lcd.ops->backlight(&priv->lcd, CHARLCD_OFF);
 	}
 
 	return 0;
diff --git a/drivers/auxdisplay/charlcd.h b/drivers/auxdisplay/charlcd.h
index 00911ad0f3deb..993f03652f2a8 100644
--- a/drivers/auxdisplay/charlcd.h
+++ b/drivers/auxdisplay/charlcd.h
@@ -9,6 +9,11 @@
 #ifndef _CHARLCD_H
 #define _CHARLCD_H
 
+enum charlcd_onoff {
+	CHARLCD_OFF = 0,
+	CHARLCD_ON,
+};
+
 struct charlcd {
 	const struct charlcd_ops *ops;
 	const unsigned char *char_conv;	/* Optional */
-- 
2.53.0

[PATCH 5.10.y 2/2] auxdisplay: charlcd: cancel backlight work on registration failure

[Sasha Levin]

From: Hongyan Xu <getshell@seu.edu.cn>

[ Upstream commit e3e3bf40916c1e810df03958cfa7ba6883cdce79 ]

With CONFIG_CHARLCD_BL_FLASH, charlcd_init() schedules bl_work before
charlcd_register() calls misc_register(). If registration fails, the
caller frees the charlcd object while delayed work still contains its
address.

Add charlcd_deinit() to cancel the delayed work and turn the backlight
off. Use it for both registration rollback and normal unregistration.

Fixes: 39f8ea46724e ("auxdisplay: charlcd: Extract character LCD core from misc/panel")
Cc: stable@vger.kernel.org
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Hongyan Xu <getshell@seu.edu.cn>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/auxdisplay/charlcd.c | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/drivers/auxdisplay/charlcd.c b/drivers/auxdisplay/charlcd.c
index e74e25ff030b2..b3ff514f91a78 100644
--- a/drivers/auxdisplay/charlcd.c
+++ b/drivers/auxdisplay/charlcd.c
@@ -779,6 +779,16 @@ static int charlcd_init(struct charlcd *lcd)
 	return 0;
 }
 
+static void charlcd_deinit(struct charlcd *lcd)
+{
+	struct charlcd_priv *priv = charlcd_to_priv(lcd);
+
+	if (lcd->ops->backlight) {
+		cancel_delayed_work_sync(&priv->bl_work);
+		lcd->ops->backlight(lcd, CHARLCD_OFF);
+	}
+}
+
 struct charlcd *charlcd_alloc(unsigned int drvdata_size)
 {
 	struct charlcd_priv *priv;
@@ -843,8 +853,10 @@ int charlcd_register(struct charlcd *lcd)
 		return ret;
 
 	ret = misc_register(&charlcd_dev);
-	if (ret)
+	if (ret) {
+		charlcd_deinit(lcd);
 		return ret;
+	}
 
 	the_charlcd = lcd;
 	register_reboot_notifier(&panel_notifier);
@@ -854,16 +866,11 @@ EXPORT_SYMBOL_GPL(charlcd_register);
 
 int charlcd_unregister(struct charlcd *lcd)
 {
-	struct charlcd_priv *priv = charlcd_to_priv(lcd);
-
 	unregister_reboot_notifier(&panel_notifier);
 	charlcd_puts(lcd, "\x0cLCD driver unloaded.\x1b[Lc\x1b[Lb\x1b[L-");
 	misc_deregister(&charlcd_dev);
 	the_charlcd = NULL;
-	if (lcd->ops->backlight) {
-		cancel_delayed_work_sync(&priv->bl_work);
-		priv->lcd.ops->backlight(&priv->lcd, CHARLCD_OFF);
-	}
+	charlcd_deinit(lcd);
 
 	return 0;
 }
-- 
2.53.0