[PATCH 1/2] fbdev: remove fb_notify support

[PATCH 1/2] fbdev: remove fb_notify support

[Arnd Bergmann]

From: Arnd Bergmann <arnd@arndb.de>

Commit dc2139c0aa32 ("leds: backlight trigger: Replace fb events with a
dedicated function call") removed the FB_EVENT_BLANK notifier, and now
the only remaining user of the FB notifier is the metronomefb driver on
the PXA/AM200EPD board.

This was introduced in commit 922613436ae5 ("[ARM] 5200/1: am200epd: use
fb notifiers and gpio api"), which converted it from an earlier version,
but as far as I can tell this can never have worked because the notifier
is called after the data it passes down is accessed.

Commit 867187821e5e ("fbdev/metronomefb: Use struct fb_info.screen_buffer")
broke this further, and there are likely other parts of the driver that
no longer work.

The am200epd board support itself should have also been removed long ago,
as there are no users and it was never converted to devicetree format.

Mark the board as broken to prevent build failures and remove the now
unused notifiers.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 arch/arm/mach-pxa/Kconfig            |  1 +
 drivers/video/fbdev/core/Makefile    |  1 -
 drivers/video/fbdev/core/fb_notify.c | 54 ----------------------------
 drivers/video/fbdev/core/fbmem.c     | 15 --------
 include/linux/fb.h                   | 21 -----------
 5 files changed, 1 insertion(+), 91 deletions(-)
 delete mode 100644 drivers/video/fbdev/core/fb_notify.c

diff --git a/arch/arm/mach-pxa/Kconfig b/arch/arm/mach-pxa/Kconfig
index 10e472f4fa43..edefc953e4f9 100644
--- a/arch/arm/mach-pxa/Kconfig
+++ b/arch/arm/mach-pxa/Kconfig
@@ -69,6 +69,7 @@ choice
 
 config GUMSTIX_AM200EPD
 	bool "Enable AM200EPD board support"
+	depends on BROKEN
 
 config GUMSTIX_AM300EPD
 	bool "Enable AM300EPD board support"
diff --git a/drivers/video/fbdev/core/Makefile b/drivers/video/fbdev/core/Makefile
index d15974759086..ac8036209501 100644
--- a/drivers/video/fbdev/core/Makefile
+++ b/drivers/video/fbdev/core/Makefile
@@ -1,5 +1,4 @@
 # SPDX-License-Identifier: GPL-2.0
-obj-$(CONFIG_FB_NOTIFY)           += fb_notify.o
 obj-$(CONFIG_FB_CORE)             += fb.o
 fb-y                              := fb_info.o \
                                      fbmem.o fbcmap.o \
diff --git a/drivers/video/fbdev/core/fb_notify.c b/drivers/video/fbdev/core/fb_notify.c
deleted file mode 100644
index 10e3b9a74adc..000000000000
--- a/drivers/video/fbdev/core/fb_notify.c
+++ /dev/null
@@ -1,54 +0,0 @@
-/*
- *  linux/drivers/video/fb_notify.c
- *
- *  Copyright (C) 2006 Antonino Daplas <adaplas@pol.net>
- *
- *	2001 - Documented with DocBook
- *	- Brad Douglas <brad@neruo.com>
- *
- * This file is subject to the terms and conditions of the GNU General Public
- * License.  See the file COPYING in the main directory of this archive
- * for more details.
- */
-#include <linux/fb.h>
-#include <linux/notifier.h>
-#include <linux/export.h>
-
-static BLOCKING_NOTIFIER_HEAD(fb_notifier_list);
-
-/**
- *	fb_register_client - register a client notifier
- *	@nb: notifier block to callback on events
- *
- *	Return: 0 on success, negative error code on failure.
- */
-int fb_register_client(struct notifier_block *nb)
-{
-	return blocking_notifier_chain_register(&fb_notifier_list, nb);
-}
-EXPORT_SYMBOL(fb_register_client);
-
-/**
- *	fb_unregister_client - unregister a client notifier
- *	@nb: notifier block to callback on events
- *
- *	Return: 0 on success, negative error code on failure.
- */
-int fb_unregister_client(struct notifier_block *nb)
-{
-	return blocking_notifier_chain_unregister(&fb_notifier_list, nb);
-}
-EXPORT_SYMBOL(fb_unregister_client);
-
-/**
- * fb_notifier_call_chain - notify clients of fb_events
- * @val: value passed to callback
- * @v: pointer passed to callback
- *
- * Return: The return value of the last notifier function
- */
-int fb_notifier_call_chain(unsigned long val, void *v)
-{
-	return blocking_notifier_call_chain(&fb_notifier_list, val, v);
-}
-EXPORT_SYMBOL_GPL(fb_notifier_call_chain);
diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
index dfcf5e4d1d4c..82ec7351e7da 100644
--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c
@@ -498,14 +498,6 @@ static int do_register_framebuffer(struct fb_info *fb_info)
 	num_registered_fb++;
 	registered_fb[i] = fb_info;
 
-#ifdef CONFIG_GUMSTIX_AM200EPD
-	{
-		struct fb_event event;
-		event.info = fb_info;
-		fb_notifier_call_chain(FB_EVENT_FB_REGISTERED, &event);
-	}
-#endif
-
 	return fbcon_fb_registered(fb_info);
 }
 
@@ -544,13 +536,6 @@ static void do_unregister_framebuffer(struct fb_info *fb_info)
 	fb_destroy_modelist(&fb_info->modelist);
 	registered_fb[fb_info->node] = NULL;
 	num_registered_fb--;
-#ifdef CONFIG_GUMSTIX_AM200EPD
-	{
-		struct fb_event event;
-		event.info = fb_info;
-		fb_notifier_call_chain(FB_EVENT_FB_UNREGISTERED, &event);
-	}
-#endif
 	fbcon_fb_unregistered(fb_info);
 
 	/* this may free fb info */
diff --git a/include/linux/fb.h b/include/linux/fb.h
index 05cc251035da..520ad870b8b2 100644
--- a/include/linux/fb.h
+++ b/include/linux/fb.h
@@ -151,27 +151,6 @@ struct fb_blit_caps {
 	u32 flags;
 };
 
-#ifdef CONFIG_FB_NOTIFY
-extern int fb_register_client(struct notifier_block *nb);
-extern int fb_unregister_client(struct notifier_block *nb);
-extern int fb_notifier_call_chain(unsigned long val, void *v);
-#else
-static inline int fb_register_client(struct notifier_block *nb)
-{
-	return 0;
-};
-
-static inline int fb_unregister_client(struct notifier_block *nb)
-{
-	return 0;
-};
-
-static inline int fb_notifier_call_chain(unsigned long val, void *v)
-{
-	return 0;
-};
-#endif
-
 /*
  * Pixmap structure definition
  *
-- 
2.39.5

Re: [PATCH 1/2] fbdev: remove fb_notify support

[Thomas Zimmermann]

Hi

Am 25.06.25 um 15:12 schrieb Arnd Bergmann:
> From: Arnd Bergmann <arnd@arndb.de>
>
> Commit dc2139c0aa32 ("leds: backlight trigger: Replace fb events with a
> dedicated function call") removed the FB_EVENT_BLANK notifier, and now
> the only remaining user of the FB notifier is the metronomefb driver on
> the PXA/AM200EPD board.
>
> This was introduced in commit 922613436ae5 ("[ARM] 5200/1: am200epd: use
> fb notifiers and gpio api"), which converted it from an earlier version,
> but as far as I can tell this can never have worked because the notifier
> is called after the data it passes down is accessed.
>
> Commit 867187821e5e ("fbdev/metronomefb: Use struct fb_info.screen_buffer")
> broke this further, and there are likely other parts of the driver that
> no longer work.
>
> The am200epd board support itself should have also been removed long ago,
> as there are no users and it was never converted to devicetree format.
>
> Mark the board as broken to prevent build failures and remove the now
> unused notifiers.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>   arch/arm/mach-pxa/Kconfig            |  1 +
>   drivers/video/fbdev/core/Makefile    |  1 -
>   drivers/video/fbdev/core/fb_notify.c | 54 ----------------------------
>   drivers/video/fbdev/core/fbmem.c     | 15 --------
>   include/linux/fb.h                   | 21 -----------
>   5 files changed, 1 insertion(+), 91 deletions(-)
>   delete mode 100644 drivers/video/fbdev/core/fb_notify.c
>
> diff --git a/arch/arm/mach-pxa/Kconfig b/arch/arm/mach-pxa/Kconfig
> index 10e472f4fa43..edefc953e4f9 100644
> --- a/arch/arm/mach-pxa/Kconfig
> +++ b/arch/arm/mach-pxa/Kconfig
> @@ -69,6 +69,7 @@ choice
>   
>   config GUMSTIX_AM200EPD
>   	bool "Enable AM200EPD board support"
> +	depends on BROKEN

If anyone wants to revive this board, we can add direct calls from fbdev 
to the board helpers.

>   
>   config GUMSTIX_AM300EPD
>   	bool "Enable AM300EPD board support"
> diff --git a/drivers/video/fbdev/core/Makefile b/drivers/video/fbdev/core/Makefile
> index d15974759086..ac8036209501 100644
> --- a/drivers/video/fbdev/core/Makefile
> +++ b/drivers/video/fbdev/core/Makefile
> @@ -1,5 +1,4 @@
>   # SPDX-License-Identifier: GPL-2.0
> -obj-$(CONFIG_FB_NOTIFY)           += fb_notify.o
>   obj-$(CONFIG_FB_CORE)             += fb.o
>   fb-y                              := fb_info.o \
>                                        fbmem.o fbcmap.o \
> diff --git a/drivers/video/fbdev/core/fb_notify.c b/drivers/video/fbdev/core/fb_notify.c
> deleted file mode 100644
> index 10e3b9a74adc..000000000000
> --- a/drivers/video/fbdev/core/fb_notify.c
> +++ /dev/null
> @@ -1,54 +0,0 @@
> -/*
> - *  linux/drivers/video/fb_notify.c
> - *
> - *  Copyright (C) 2006 Antonino Daplas <adaplas@pol.net>
> - *
> - *	2001 - Documented with DocBook
> - *	- Brad Douglas <brad@neruo.com>
> - *
> - * This file is subject to the terms and conditions of the GNU General Public
> - * License.  See the file COPYING in the main directory of this archive
> - * for more details.
> - */
> -#include <linux/fb.h>
> -#include <linux/notifier.h>
> -#include <linux/export.h>
> -
> -static BLOCKING_NOTIFIER_HEAD(fb_notifier_list);
> -
> -/**
> - *	fb_register_client - register a client notifier
> - *	@nb: notifier block to callback on events
> - *
> - *	Return: 0 on success, negative error code on failure.
> - */
> -int fb_register_client(struct notifier_block *nb)
> -{
> -	return blocking_notifier_chain_register(&fb_notifier_list, nb);
> -}
> -EXPORT_SYMBOL(fb_register_client);
> -
> -/**
> - *	fb_unregister_client - unregister a client notifier
> - *	@nb: notifier block to callback on events
> - *
> - *	Return: 0 on success, negative error code on failure.
> - */
> -int fb_unregister_client(struct notifier_block *nb)
> -{
> -	return blocking_notifier_chain_unregister(&fb_notifier_list, nb);
> -}
> -EXPORT_SYMBOL(fb_unregister_client);
> -
> -/**
> - * fb_notifier_call_chain - notify clients of fb_events
> - * @val: value passed to callback
> - * @v: pointer passed to callback
> - *
> - * Return: The return value of the last notifier function
> - */
> -int fb_notifier_call_chain(unsigned long val, void *v)
> -{
> -	return blocking_notifier_call_chain(&fb_notifier_list, val, v);
> -}
> -EXPORT_SYMBOL_GPL(fb_notifier_call_chain);
> diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
> index dfcf5e4d1d4c..82ec7351e7da 100644
> --- a/drivers/video/fbdev/core/fbmem.c
> +++ b/drivers/video/fbdev/core/fbmem.c
> @@ -498,14 +498,6 @@ static int do_register_framebuffer(struct fb_info *fb_info)
>   	num_registered_fb++;
>   	registered_fb[i] = fb_info;
>   
> -#ifdef CONFIG_GUMSTIX_AM200EPD
> -	{
> -		struct fb_event event;
> -		event.info = fb_info;
> -		fb_notifier_call_chain(FB_EVENT_FB_REGISTERED, &event);

These FB_EVENT_ constants need to go as well. The whole block starting 
at https://elixir.bootlin.com/linux/v6.16-rc3/source/include/linux/fb.h#L128

With that:

Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>

Best regards
Thomas

> -	}
> -#endif
> -
>   	return fbcon_fb_registered(fb_info);
>   }
>   
> @@ -544,13 +536,6 @@ static void do_unregister_framebuffer(struct fb_info *fb_info)
>   	fb_destroy_modelist(&fb_info->modelist);
>   	registered_fb[fb_info->node] = NULL;
>   	num_registered_fb--;
> -#ifdef CONFIG_GUMSTIX_AM200EPD
> -	{
> -		struct fb_event event;
> -		event.info = fb_info;
> -		fb_notifier_call_chain(FB_EVENT_FB_UNREGISTERED, &event);
> -	}
> -#endif
>   	fbcon_fb_unregistered(fb_info);
>   
>   	/* this may free fb info */
> diff --git a/include/linux/fb.h b/include/linux/fb.h
> index 05cc251035da..520ad870b8b2 100644
> --- a/include/linux/fb.h
> +++ b/include/linux/fb.h
> @@ -151,27 +151,6 @@ struct fb_blit_caps {
>   	u32 flags;
>   };
>   
> -#ifdef CONFIG_FB_NOTIFY
> -extern int fb_register_client(struct notifier_block *nb);
> -extern int fb_unregister_client(struct notifier_block *nb);
> -extern int fb_notifier_call_chain(unsigned long val, void *v);
> -#else
> -static inline int fb_register_client(struct notifier_block *nb)
> -{
> -	return 0;
> -};
> -
> -static inline int fb_unregister_client(struct notifier_block *nb)
> -{
> -	return 0;
> -};
> -
> -static inline int fb_notifier_call_chain(unsigned long val, void *v)
> -{
> -	return 0;
> -};
> -#endif
> -
>   /*
>    * Pixmap structure definition
>    *

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)

Re: [PATCH 1/2] fbdev: remove fb_notify support

[Sam Ravnborg]

Hi Arnd.

I remember I stared at this code before, good to see it gone.
There is a bit more tidiying up you can do.

Also, I suggest to split it in two patches, it itches me to see the
driver specific part mixed up with the fb_notify removal.

	Sam


On Wed, Jun 25, 2025 at 03:12:22PM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
> 
> Commit dc2139c0aa32 ("leds: backlight trigger: Replace fb events with a
> dedicated function call") removed the FB_EVENT_BLANK notifier, and now
> the only remaining user of the FB notifier is the metronomefb driver on
> the PXA/AM200EPD board.
> 
> This was introduced in commit 922613436ae5 ("[ARM] 5200/1: am200epd: use
> fb notifiers and gpio api"), which converted it from an earlier version,
> but as far as I can tell this can never have worked because the notifier
> is called after the data it passes down is accessed.
> 
> Commit 867187821e5e ("fbdev/metronomefb: Use struct fb_info.screen_buffer")
> broke this further, and there are likely other parts of the driver that
> no longer work.
> 
> The am200epd board support itself should have also been removed long ago,
> as there are no users and it was never converted to devicetree format.
> 
> Mark the board as broken to prevent build failures and remove the now
> unused notifiers.
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>  arch/arm/mach-pxa/Kconfig            |  1 +
This is mixing things up a bit. I suggest
splitting the "depends on BROKEN" out in a dedicated patch.

>  drivers/video/fbdev/core/Makefile    |  1 -
>  drivers/video/fbdev/core/fb_notify.c | 54 ----------------------------
>  drivers/video/fbdev/core/fbmem.c     | 15 --------
>  include/linux/fb.h                   | 21 -----------
>  5 files changed, 1 insertion(+), 91 deletions(-)
>  delete mode 100644 drivers/video/fbdev/core/fb_notify.c
> 
> diff --git a/arch/arm/mach-pxa/Kconfig b/arch/arm/mach-pxa/Kconfig
> index 10e472f4fa43..edefc953e4f9 100644
> --- a/arch/arm/mach-pxa/Kconfig
> +++ b/arch/arm/mach-pxa/Kconfig
> @@ -69,6 +69,7 @@ choice
>  
>  config GUMSTIX_AM200EPD
>  	bool "Enable AM200EPD board support"
> +	depends on BROKEN
>  
>  config GUMSTIX_AM300EPD
>  	bool "Enable AM300EPD board support"
> diff --git a/drivers/video/fbdev/core/Makefile b/drivers/video/fbdev/core/Makefile
> index d15974759086..ac8036209501 100644
> --- a/drivers/video/fbdev/core/Makefile
> +++ b/drivers/video/fbdev/core/Makefile
> @@ -1,5 +1,4 @@
>  # SPDX-License-Identifier: GPL-2.0
> -obj-$(CONFIG_FB_NOTIFY)           += fb_notify.o
>  obj-$(CONFIG_FB_CORE)             += fb.o
>  fb-y                              := fb_info.o \
>                                       fbmem.o fbcmap.o \
> diff --git a/drivers/video/fbdev/core/fb_notify.c b/drivers/video/fbdev/core/fb_notify.c
> deleted file mode 100644
> index 10e3b9a74adc..000000000000
> --- a/drivers/video/fbdev/core/fb_notify.c
> +++ /dev/null
> @@ -1,54 +0,0 @@
> -/*
> - *  linux/drivers/video/fb_notify.c
> - *
> - *  Copyright (C) 2006 Antonino Daplas <adaplas@pol.net>
> - *
> - *	2001 - Documented with DocBook
> - *	- Brad Douglas <brad@neruo.com>
> - *
> - * This file is subject to the terms and conditions of the GNU General Public
> - * License.  See the file COPYING in the main directory of this archive
> - * for more details.
> - */
> -#include <linux/fb.h>
> -#include <linux/notifier.h>
> -#include <linux/export.h>
> -
> -static BLOCKING_NOTIFIER_HEAD(fb_notifier_list);
> -
> -/**
> - *	fb_register_client - register a client notifier
> - *	@nb: notifier block to callback on events
> - *
> - *	Return: 0 on success, negative error code on failure.
> - */
> -int fb_register_client(struct notifier_block *nb)
> -{
> -	return blocking_notifier_chain_register(&fb_notifier_list, nb);
> -}
> -EXPORT_SYMBOL(fb_register_client);
> -
> -/**
> - *	fb_unregister_client - unregister a client notifier
> - *	@nb: notifier block to callback on events
> - *
> - *	Return: 0 on success, negative error code on failure.
> - */
> -int fb_unregister_client(struct notifier_block *nb)
> -{
> -	return blocking_notifier_chain_unregister(&fb_notifier_list, nb);
> -}
> -EXPORT_SYMBOL(fb_unregister_client);
> -
> -/**
> - * fb_notifier_call_chain - notify clients of fb_events
> - * @val: value passed to callback
> - * @v: pointer passed to callback
> - *
> - * Return: The return value of the last notifier function
> - */
> -int fb_notifier_call_chain(unsigned long val, void *v)
> -{
> -	return blocking_notifier_call_chain(&fb_notifier_list, val, v);
> -}
> -EXPORT_SYMBOL_GPL(fb_notifier_call_chain);
> diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
> index dfcf5e4d1d4c..82ec7351e7da 100644
> --- a/drivers/video/fbdev/core/fbmem.c
> +++ b/drivers/video/fbdev/core/fbmem.c
> @@ -498,14 +498,6 @@ static int do_register_framebuffer(struct fb_info *fb_info)
>  	num_registered_fb++;
>  	registered_fb[i] = fb_info;
>  
> -#ifdef CONFIG_GUMSTIX_AM200EPD
> -	{
> -		struct fb_event event;
Drop the fb_event definition, it is no longer used.

> -		event.info = fb_info;
> -		fb_notifier_call_chain(FB_EVENT_FB_REGISTERED, &event);
Drop the define for FB_EVENT_FB_REGISTERED

> -	}
> -#endif
> -
>  	return fbcon_fb_registered(fb_info);
>  }
>  
> @@ -544,13 +536,6 @@ static void do_unregister_framebuffer(struct fb_info *fb_info)
>  	fb_destroy_modelist(&fb_info->modelist);
>  	registered_fb[fb_info->node] = NULL;
>  	num_registered_fb--;
> -#ifdef CONFIG_GUMSTIX_AM200EPD
> -	{
> -		struct fb_event event;
> -		event.info = fb_info;
> -		fb_notifier_call_chain(FB_EVENT_FB_UNREGISTERED, &event);
Drop the define for FB_EVENT_FB_UNREGISTERED

> -	}
> -#endif
>  	fbcon_fb_unregistered(fb_info);
>  
>  	/* this may free fb info */
> diff --git a/include/linux/fb.h b/include/linux/fb.h
> index 05cc251035da..520ad870b8b2 100644
> --- a/include/linux/fb.h
> +++ b/include/linux/fb.h
> @@ -151,27 +151,6 @@ struct fb_blit_caps {
>  	u32 flags;
>  };
>  
> -#ifdef CONFIG_FB_NOTIFY

The Kconfig symbol FB_NOTIFY should be dropped as well.


> -extern int fb_register_client(struct notifier_block *nb);
Drop forward for notifier_block, last user in the file is gone.

> -extern int fb_unregister_client(struct notifier_block *nb);
> -extern int fb_notifier_call_chain(unsigned long val, void *v);
> -#else
> -static inline int fb_register_client(struct notifier_block *nb)
> -{
> -	return 0;
> -};
> -
> -static inline int fb_unregister_client(struct notifier_block *nb)
> -{
> -	return 0;
> -};
> -
> -static inline int fb_notifier_call_chain(unsigned long val, void *v)
> -{
> -	return 0;
> -};
> -#endif
> -
>  /*
>   * Pixmap structure definition
>   *
> -- 
> 2.39.5

Re: [PATCH 1/2] fbdev: remove fb_notify support

[Helge Deller]

Hi Arnd,

On 6/25/25 17:20, Sam Ravnborg wrote:
> Hi Arnd.
> 
> I remember I stared at this code before, good to see it gone.
> There is a bit more tidiying up you can do.
> 
> Also, I suggest to split it in two patches, it itches me to see the
> driver specific part mixed up with the fb_notify removal.

I assume you will send a v2 patch series.
If so, I'm happy to take it then.

Thanks!
Helge