linux-kernel - Re: [PATCH 24/33] Revert "backlight/fbcon: Add FB_EVENT

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Message-ID: <20190611140929.ufkz3rz3pjw75qgy@holly.lan>
Date:   Tue, 11 Jun 2019 15:09:29 +0100
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     Daniel Vetter <daniel.vetter@...ll.ch>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
        linux-fbdev@...r.kernel.org,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Richard Purdie <rpurdie@...ys.net>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Sam Ravnborg <sam@...nborg.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Lee Jones <lee.jones@...aro.org>,
        Jingoo Han <jingoohan1@...il.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Yisheng Xie <ysxie@...mail.com>
Subject: Re: [PATCH 24/33] Revert "backlight/fbcon: Add FB_EVENT_CONBLANK"

On Tue, May 28, 2019 at 11:02:55AM +0200, Daniel Vetter wrote:
> This reverts commit 994efacdf9a087b52f71e620b58dfa526b0cf928.
> 
> The justification is that if hw blanking fails (i.e. fbops->fb_blank)
> fails, then we still want to shut down the backlight. Which is exactly
> _not_ what fb_blank() does and so rather inconsistent if we end up
> with different behaviour between fbcon and direct fbdev usage. Given
> that the entire notifier maze is getting in the way anyway I figured
> it's simplest to revert this not well justified commit.
> 
> v2: Add static inline to the dummy version.
> 
> Cc: Richard Purdie <rpurdie@...ys.net>
> Signed-off-by: Daniel Vetter <daniel.vetter@...el.com>
> Reviewed-by: Sam Ravnborg <sam@...nborg.org>
> Reviewed-by: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>
> Cc: Lee Jones <lee.jones@...aro.org>
> Cc: Daniel Thompson <daniel.thompson@...aro.org>
> Cc: Jingoo Han <jingoohan1@...il.com>
> Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
> Cc: Daniel Vetter <daniel.vetter@...ll.ch>
> Cc: Hans de Goede <hdegoede@...hat.com>
> Cc: Yisheng Xie <ysxie@...mail.com>
> Cc: linux-fbdev@...r.kernel.org

This was the main patch where I wanted the bigger picture ;-) and TBH
I'm still in two minds here. I don't personally view fbcon as
inconsistent, more that, as an in-kernel service it might have to do
more that something more complicated than freak out and let userspace
decide what to do next.

However... since I'm struggling to make up my mind, I can't think of
many products that would ship reliant exclusively on fbcon *and* this
patch is more about fbcon than backlight then I figure that, from a
backlight perspective:

Acked-by: Daniel Thompson <daniel.thompson@...aro.org>


Daniel.


> ---
>  drivers/video/backlight/backlight.c |  2 +-
>  drivers/video/fbdev/core/fbcon.c    | 14 +-------------
>  drivers/video/fbdev/core/fbmem.c    |  1 +
>  include/linux/fb.h                  |  4 +---
>  include/linux/fbcon.h               |  2 ++
>  5 files changed, 6 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
> index 1ef8b6fd62ac..5dc07106a59e 100644
> --- a/drivers/video/backlight/backlight.c
> +++ b/drivers/video/backlight/backlight.c
> @@ -47,7 +47,7 @@ static int fb_notifier_callback(struct notifier_block *self,
>  	int fb_blank = 0;
>  
>  	/* If we aren't interested in this event, skip it immediately ... */
> -	if (event != FB_EVENT_BLANK && event != FB_EVENT_CONBLANK)
> +	if (event != FB_EVENT_BLANK)
>  		return 0;
>  
>  	bd = container_of(self, struct backlight_device, fb_notif);
> diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
> index ef69bd4ad343..a4617067ff24 100644
> --- a/drivers/video/fbdev/core/fbcon.c
> +++ b/drivers/video/fbdev/core/fbcon.c
> @@ -2350,8 +2350,6 @@ static int fbcon_switch(struct vc_data *vc)
>  static void fbcon_generic_blank(struct vc_data *vc, struct fb_info *info,
>  				int blank)
>  {
> -	struct fb_event event;
> -
>  	if (blank) {
>  		unsigned short charmask = vc->vc_hi_font_mask ?
>  			0x1ff : 0xff;
> @@ -2362,13 +2360,6 @@ static void fbcon_generic_blank(struct vc_data *vc, struct fb_info *info,
>  		fbcon_clear(vc, 0, 0, vc->vc_rows, vc->vc_cols);
>  		vc->vc_video_erase_char = oldc;
>  	}
> -
> -
> -	lock_fb_info(info);
> -	event.info = info;
> -	event.data = &blank;
> -	fb_notifier_call_chain(FB_EVENT_CONBLANK, &event);
> -	unlock_fb_info(info);
>  }
>  
>  static int fbcon_blank(struct vc_data *vc, int blank, int mode_switch)
> @@ -3240,7 +3231,7 @@ int fbcon_fb_registered(struct fb_info *info)
>  	return ret;
>  }
>  
> -static void fbcon_fb_blanked(struct fb_info *info, int blank)
> +void fbcon_fb_blanked(struct fb_info *info, int blank)
>  {
>  	struct fbcon_ops *ops = info->fbcon_par;
>  	struct vc_data *vc;
> @@ -3344,9 +3335,6 @@ static int fbcon_event_notify(struct notifier_block *self,
>  		con2fb = event->data;
>  		con2fb->framebuffer = con2fb_map[con2fb->console - 1];
>  		break;
> -	case FB_EVENT_BLANK:
> -		fbcon_fb_blanked(info, *(int *)event->data);
> -		break;
>  	case FB_EVENT_REMAP_ALL_CONSOLE:
>  		idx = info->node;
>  		fbcon_remap_all(idx);
> diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
> index ddc0c16b8bbf..9366fbe99a58 100644
> --- a/drivers/video/fbdev/core/fbmem.c
> +++ b/drivers/video/fbdev/core/fbmem.c
> @@ -1068,6 +1068,7 @@ fb_blank(struct fb_info *info, int blank)
>  	event.data = &blank;
>  
>  	early_ret = fb_notifier_call_chain(FB_EARLY_EVENT_BLANK, &event);
> +	fbcon_fb_blanked(info, blank);
>  
>  	if (info->fbops->fb_blank)
>   		ret = info->fbops->fb_blank(blank, info);
> diff --git a/include/linux/fb.h b/include/linux/fb.h
> index 0d86aa31bf8d..1e66fac3124f 100644
> --- a/include/linux/fb.h
> +++ b/include/linux/fb.h
> @@ -137,12 +137,10 @@ struct fb_cursor_user {
>  #define FB_EVENT_GET_CONSOLE_MAP        0x07
>  /*      CONSOLE-SPECIFIC: set console to framebuffer mapping */
>  #define FB_EVENT_SET_CONSOLE_MAP        0x08
> -/*      A hardware display blank change occurred */
> +/*      A display blank is requested       */
>  #define FB_EVENT_BLANK                  0x09
>  /*      Private modelist is to be replaced */
>  #define FB_EVENT_MODE_CHANGE_ALL	0x0B
> -/*	A software display blank change occurred */
> -#define FB_EVENT_CONBLANK               0x0C
>  /*      CONSOLE-SPECIFIC: remap all consoles to new fb - for vga_switcheroo */
>  #define FB_EVENT_REMAP_ALL_CONSOLE      0x0F
>  /*      A hardware display blank early change occurred */
> diff --git a/include/linux/fbcon.h b/include/linux/fbcon.h
> index 305e4f2eddac..d67d7ec51ef9 100644
> --- a/include/linux/fbcon.h
> +++ b/include/linux/fbcon.h
> @@ -14,6 +14,7 @@ int fbcon_mode_deleted(struct fb_info *info,
>  void fbcon_new_modelist(struct fb_info *info);
>  void fbcon_get_requirement(struct fb_info *info,
>  			   struct fb_blit_caps *caps);
> +void fbcon_fb_blanked(struct fb_info *info, int blank);
>  #else
>  static inline void fb_console_init(void) {}
>  static inline void fb_console_exit(void) {}
> @@ -27,6 +28,7 @@ static inline int fbcon_mode_deleted(struct fb_info *info,
>  static inline void fbcon_new_modelist(struct fb_info *info) {}
>  static inline void fbcon_get_requirement(struct fb_info *info,
>  					 struct fb_blit_caps *caps) {}
> +static inline void fbcon_fb_blanked(struct fb_info *info, int blank) {}
>  #endif
>  
>  #endif /* _LINUX_FBCON_H */
> -- 
> 2.20.1
>