On Tue, Jun 11, 2019 at 03:09:29PM +0100, Daniel Thompson wrote:

On Tue, May 28, 2019 at 11:02:55AM +0200, Daniel Vetter wrote:

quoted

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 <redacted>
Signed-off-by: Daniel Vetter <redacted>
Reviewed-by: Sam Ravnborg <redacted>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Lee Jones <redacted>
Cc: Daniel Thompson <redacted>
Cc: Jingoo Han <jingoohan1@gmail.com>
Cc: Bartlomiej Zolnierkiewicz <redacted>
Cc: Daniel Vetter <redacted>
Cc: Hans de Goede <redacted>
Cc: Yisheng Xie <redacted>
Cc: linux-fbdev@vger.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.

I think the story is even worse, at least for drm-based drivers:

- We have the fbcon code here, which did something slightly different than
  fbdev modesets called through /dev/fb*.

- For most x86 drivers the expectations is that userspace handles the
  backlight over modesets (enabling/disabling as needed), and the rules
  for which backlight to pick extremely arcane: There's no link in sysfs
  or anywhere else from a drm connector to the corresponding backlight
  device.

- But some other drivers, mostly on the soc side, handle backlight
  enabling/disabling themselves, as part of the usual drm modeset
  sequence. And I suspect that at least some drm userspace more geared
  towards userspace doesn't bother handling the backlight on its own.

I don't have any plan yet how to get us out of this whole, but figured
this patch here should at least simplifiy things a bit.

Just fyi a bit more context here, I think there's more work to do :-/
-Daniel

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 <redacted>


Daniel.

quoted

---
 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 = ␣
-	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 = ␣
 
 	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

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch