[PATCH v4 0/3] console/fbcon: Add support for deferred console takeover

[PATCH v4 0/3] console/fbcon: Add support for deferred console takeover

[Hans de Goede]

Hi All,

Here is v4 of my patch-set, to delay fbcon taking over the console (and
binding to fbdev devices) until there actually is some text output to the
console. This is intended for use with the "quiet" cmdline option, in
combination with a bootloader which leaves the vendor's logo /
EFI bootgraphics put up by the firmware intact on the EFI framebuffer.

The end goal here is a boot where the firmware shows its boot graphics
and these stay in place for a couple of seconds until the GUI loads and
the GUI then smoothly takes over the framebuffer without any distruptions.

This patch-set spans 2 subsystems.

Petr, the printk subsys change is really trivial (1 line addition) can we
get your Acked-by for merging all 3 patches through the fbdev tree?

Changelog:

Changes in v4:
-Keep the comments about which fbcon functions need locks in place

Changes in v3:
-Export is_console_locke() for use in modules (as fbcon may be built as a .ko)
-Use WARN_CONSOLE_UNLOCKED() in several places in the fbcon code to assert
 proper locking (requested by Daniel)
-Unregister the fbcon-dummycon-output-notifier on fbcon_exit() (req. by Daniel)
-Document the fbcon=nodefer commandline option (req. by Emil)

Changes in v2:
-Check the whole string when checking for erases in putcs, instead of just
 the first char
-Make dummycon_blank return 1, so that a redraw gets triggered and any text
 rendered while blanked gets output so that it can trigger a deferred
 takeover if one is pending

Regards,

Hans
 

[PATCH v3 1/3] printk: Export is_console_locked

[Hans de Goede]

This is a preparation patch for adding a number of WARN_CONSOLE_UNLOCKED()
calls to the fbcon code, which may be built as a module (event though
usually it is not).

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
Changes in v3:
-New patch in v3 of this patchset
---
 kernel/printk/printk.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 247808333ba4..3f041e7cbfc9 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2243,6 +2243,7 @@ int is_console_locked(void)
 {
 	return console_locked;
 }
+EXPORT_SYMBOL(is_console_locked);
 
 /*
  * Check if we have any console that is capable of printing while cpu is
-- 
2.17.1

[PATCH v3 2/3] fbcon: Call WARN_CONSOLE_UNLOCKED() where applicable

[Hans de Goede]

Replace comments about places where the console lock should be held with
calls to WARN_CONSOLE_UNLOCKED() to assert that it is actually held.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
Changes in v3:
-New patch in v3 of this patchset

Changes in v4:
-Keep the comments about which fbcon functions need locks in place
---
 drivers/video/fbdev/core/fbcon.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
index c910e74d46ff..cd8d52a967aa 100644
--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -828,6 +828,8 @@ static int set_con2fb_map(int unit, int newidx, int user)
 	struct fb_info *oldinfo = NULL;
  	int found, err = 0;
 
+	WARN_CONSOLE_UNLOCKED();
+
 	if (oldidx == newidx)
 		return 0;
 
@@ -3044,6 +3046,8 @@ static int fbcon_fb_unbind(int idx)
 {
 	int i, new_idx = -1, ret = 0;
 
+	WARN_CONSOLE_UNLOCKED();
+
 	if (!fbcon_has_console_bind)
 		return 0;
 
@@ -3094,6 +3098,8 @@ static int fbcon_fb_unregistered(struct fb_info *info)
 {
 	int i, idx;
 
+	WARN_CONSOLE_UNLOCKED();
+
 	idx = info->node;
 	for (i = first_fb_vc; i <= last_fb_vc; i++) {
 		if (con2fb_map[i] == idx)
@@ -3131,6 +3137,9 @@ static int fbcon_fb_unregistered(struct fb_info *info)
 static void fbcon_remap_all(int idx)
 {
 	int i;
+
+	WARN_CONSOLE_UNLOCKED();
+
 	for (i = first_fb_vc; i <= last_fb_vc; i++)
 		set_con2fb_map(i, idx, 0);
 
@@ -3177,6 +3186,8 @@ static int fbcon_fb_registered(struct fb_info *info)
 {
 	int ret = 0, i, idx;
 
+	WARN_CONSOLE_UNLOCKED();
+
 	idx = info->node;
 	fbcon_select_primary(info);
 
-- 
2.17.1

[PATCH v3 3/3] console/fbcon: Add support for deferred console takeover

[Hans de Goede]

Currently fbcon claims fbdevs as soon as they are registered and takes over
the console as soon as the first fbdev gets registered.

This behavior is undesirable in cases where a smooth graphical bootup is
desired, in such cases we typically want the contents of the framebuffer
(typically a vendor logo) to stay in place as is.

The current solution for this problem (on embedded systems) is to not
enable fbcon.

This commit adds a new FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER config option,
which when enabled defers fbcon taking over the console from the dummy
console until the first text is displayed on the console. Together with the
"quiet" kernel commandline option, this allows fbcon to still be used
together with a smooth graphical bootup, having it take over the console as
soon as e.g. an error message is logged.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
Changes in v2:
-Check the whole string when checking for erases in putcs, instead of just
 the first char
-Make dummycon_blank return 1, so that a redraw gets triggered and any text
 rendered while blanked gets output so that it can trigger a deferred
 takeover if one is pending

Changes in v3:
-Call WARN_CONSOLE_UNLOCKED() from fbcon_output_notifier()
-Unregister the notifier on fbcon_exit()
-Document the fbcon=nodefer commandline option in Documentation/fb/fbcon.txt
---
 Documentation/fb/fbcon.txt       |  7 ++++
 drivers/video/console/Kconfig    | 11 +++++
 drivers/video/console/dummycon.c | 67 +++++++++++++++++++++++++----
 drivers/video/fbdev/core/fbcon.c | 72 ++++++++++++++++++++++++++++++++
 include/linux/console.h          |  5 +++
 5 files changed, 154 insertions(+), 8 deletions(-)

diff --git a/Documentation/fb/fbcon.txt b/Documentation/fb/fbcon.txt
index 79c22d096bbc..d4d642e1ce9c 100644
--- a/Documentation/fb/fbcon.txt
+++ b/Documentation/fb/fbcon.txt
@@ -155,6 +155,13 @@ C. Boot options
 	used by text. By default, this area will be black. The 'color' value
 	is an integer number that depends on the framebuffer driver being used.
 
+6. fbcon=nodefer
+
+	If the kernel is compiled with deferred fbcon takeover support, normally
+	the framebuffer contents, left in place by the firmware/bootloader, will
+	be preserved until there actually is some text is output to the console.
+	This option causes fbcon to bind immediately to the fbdev device.
+
 C. Attaching, Detaching and Unloading
 
 Before going on how to attach, detach and unload the framebuffer console, an
diff --git a/drivers/video/console/Kconfig b/drivers/video/console/Kconfig
index 4110ba7d7ca9..e91edef98633 100644
--- a/drivers/video/console/Kconfig
+++ b/drivers/video/console/Kconfig
@@ -150,6 +150,17 @@ config FRAMEBUFFER_CONSOLE_ROTATION
          such that other users of the framebuffer will remain normally
          oriented.
 
+config FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
+	bool "Framebuffer Console Deferred Takeover"
+	depends on FRAMEBUFFER_CONSOLE=y && DUMMY_CONSOLE=y
+	help
+	  If enabled this defers the framebuffer console taking over the
+	  console from the dummy console until the first text is displayed on
+	  the console. This is useful in combination with the "quiet" kernel
+	  commandline option to keep the framebuffer contents initially put up
+	  by the firmware in place, rather then replacing the contents with a
+	  black screen as soon as fbcon loads.
+
 config STI_CONSOLE
         bool "STI text console"
 	depends on PARISC && HAS_IOMEM
diff --git a/drivers/video/console/dummycon.c b/drivers/video/console/dummycon.c
index f2eafe2ed980..45ad925ad5f8 100644
--- a/drivers/video/console/dummycon.c
+++ b/drivers/video/console/dummycon.c
@@ -26,6 +26,65 @@
 #define DUMMY_ROWS	CONFIG_DUMMY_CONSOLE_ROWS
 #endif
 
+#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
+/* These are both protected by the console_lock */
+static RAW_NOTIFIER_HEAD(dummycon_output_nh);
+static bool dummycon_putc_called;
+
+void dummycon_register_output_notifier(struct notifier_block *nb)
+{
+	raw_notifier_chain_register(&dummycon_output_nh, nb);
+
+	if (dummycon_putc_called)
+		nb->notifier_call(nb, 0, NULL);
+}
+
+void dummycon_unregister_output_notifier(struct notifier_block *nb)
+{
+	raw_notifier_chain_unregister(&dummycon_output_nh, nb);
+}
+
+static void dummycon_putc(struct vc_data *vc, int c, int ypos, int xpos)
+{
+	dummycon_putc_called = true;
+	raw_notifier_call_chain(&dummycon_output_nh, 0, NULL);
+}
+
+static void dummycon_putcs(struct vc_data *vc, const unsigned short *s,
+			   int count, int ypos, int xpos)
+{
+	int i;
+
+	if (!dummycon_putc_called) {
+		/* Ignore erases */
+		for (i = 0 ; i < count; i++) {
+			if (s[i] != vc->vc_video_erase_char)
+				break;
+		}
+		if (i == count)
+			return;
+
+		dummycon_putc_called = true;
+	}
+
+	raw_notifier_call_chain(&dummycon_output_nh, 0, NULL);
+}
+
+static int dummycon_blank(struct vc_data *vc, int blank, int mode_switch)
+{
+	/* Redraw, so that we get putc(s) for output done while blanked */
+	return 1;
+}
+#else
+static void dummycon_putc(struct vc_data *vc, int c, int ypos, int xpos) { }
+static void dummycon_putcs(struct vc_data *vc, const unsigned short *s,
+			   int count, int ypos, int xpos) { }
+static int dummycon_blank(struct vc_data *vc, int blank, int mode_switch)
+{
+	return 0;
+}
+#endif
+
 static const char *dummycon_startup(void)
 {
     return "dummy device";
@@ -44,9 +103,6 @@ static void dummycon_init(struct vc_data *vc, int init)
 static void dummycon_deinit(struct vc_data *vc) { }
 static void dummycon_clear(struct vc_data *vc, int sy, int sx, int height,
 			   int width) { }
-static void dummycon_putc(struct vc_data *vc, int c, int ypos, int xpos) { }
-static void dummycon_putcs(struct vc_data *vc, const unsigned short *s,
-			   int count, int ypos, int xpos) { }
 static void dummycon_cursor(struct vc_data *vc, int mode) { }
 
 static bool dummycon_scroll(struct vc_data *vc, unsigned int top,
@@ -61,11 +117,6 @@ static int dummycon_switch(struct vc_data *vc)
 	return 0;
 }
 
-static int dummycon_blank(struct vc_data *vc, int blank, int mode_switch)
-{
-	return 0;
-}
-
 static int dummycon_font_set(struct vc_data *vc, struct console_font *font,
 			     unsigned int flags)
 {
diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
index cd8d52a967aa..5fb156bdcf4e 100644
--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -129,6 +129,12 @@ static inline void fbcon_map_override(void)
 }
 #endif /* CONFIG_FRAMEBUFFER_CONSOLE_DETECT_PRIMARY */
 
+#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
+static bool deferred_takeover = true;
+#else
+#define deferred_takeover false
+#endif
+
 /* font data */
 static char fontname[40];
 
@@ -499,6 +505,12 @@ static int __init fb_console_setup(char *this_opt)
 				margin_color = simple_strtoul(options, &options, 0);
 			continue;
 		}
+#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
+		if (!strcmp(options, "nodefer")) {
+			deferred_takeover = false;
+			continue;
+		}
+#endif
 	}
 	return 1;
 }
@@ -3100,6 +3112,9 @@ static int fbcon_fb_unregistered(struct fb_info *info)
 
 	WARN_CONSOLE_UNLOCKED();
 
+	if (deferred_takeover)
+		return 0;
+
 	idx = info->node;
 	for (i = first_fb_vc; i <= last_fb_vc; i++) {
 		if (con2fb_map[i] == idx)
@@ -3140,6 +3155,13 @@ static void fbcon_remap_all(int idx)
 
 	WARN_CONSOLE_UNLOCKED();
 
+	if (deferred_takeover) {
+		for (i = first_fb_vc; i <= last_fb_vc; i++)
+			con2fb_map_boot[i] = idx;
+		fbcon_map_override();
+		return;
+	}
+
 	for (i = first_fb_vc; i <= last_fb_vc; i++)
 		set_con2fb_map(i, idx, 0);
 
@@ -3191,6 +3213,11 @@ static int fbcon_fb_registered(struct fb_info *info)
 	idx = info->node;
 	fbcon_select_primary(info);
 
+	if (deferred_takeover) {
+		pr_info("fbcon: Deferring console take-over\n");
+		return 0;
+	}
+
 	if (info_idx == -1) {
 		for (i = first_fb_vc; i <= last_fb_vc; i++) {
 			if (con2fb_map_boot[i] == idx) {
@@ -3566,8 +3593,46 @@ static int fbcon_init_device(void)
 	return 0;
 }
 
+#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
+static struct notifier_block fbcon_output_nb;
+
+static int fbcon_output_notifier(struct notifier_block *nb,
+				 unsigned long action, void *data)
+{
+	int i;
+
+	WARN_CONSOLE_UNLOCKED();
+
+	pr_info("fbcon: Taking over console\n");
+
+	dummycon_unregister_output_notifier(&fbcon_output_nb);
+	deferred_takeover = false;
+	logo_shown = FBCON_LOGO_DONTSHOW;
+
+	for (i = 0; i < FB_MAX; i++) {
+		if (registered_fb[i])
+			fbcon_fb_registered(registered_fb[i]);
+	}
+
+	return NOTIFY_OK;
+}
+
+static void fbcon_register_output_notifier(void)
+{
+	fbcon_output_nb.notifier_call = fbcon_output_notifier;
+	dummycon_register_output_notifier(&fbcon_output_nb);
+}
+#else
+static inline void fbcon_register_output_notifier(void) {}
+#endif
+
 static void fbcon_start(void)
 {
+	if (deferred_takeover) {
+		fbcon_register_output_notifier();
+		return;
+	}
+
 	if (num_registered_fb) {
 		int i;
 
@@ -3594,6 +3659,13 @@ static void fbcon_exit(void)
 	if (fbcon_has_exited)
 		return;
 
+#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
+	if (deferred_takeover) {
+		dummycon_unregister_output_notifier(&fbcon_output_nb);
+		deferred_takeover = false;
+	}
+#endif
+
 	kfree((void *)softback_buf);
 	softback_buf = 0UL;
 
diff --git a/include/linux/console.h b/include/linux/console.h
index dfd6b0e97855..f59f3dbca65c 100644
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -21,6 +21,7 @@ struct console_font_op;
 struct console_font;
 struct module;
 struct tty_struct;
+struct notifier_block;
 
 /*
  * this is what the terminal answers to a ESC-Z or csi0c query.
@@ -220,4 +221,8 @@ static inline bool vgacon_text_force(void) { return false; }
 
 extern void console_init(void);
 
+/* For deferred console takeover */
+void dummycon_register_output_notifier(struct notifier_block *nb);
+void dummycon_unregister_output_notifier(struct notifier_block *nb);
+
 #endif /* _LINUX_CONSOLE_H */
-- 
2.17.1

Re: [PATCH v3 1/3] printk: Export is_console_locked

[Hans de Goede]

Hi,

As the cover letter's subject correctly indicates this is v4 of the
patch-set, I forgot to bump the subject-prefix when sending, so the
v3 in the subject here really should be v4.

Regards,

Hans


On 26-06-18 20:36, Hans de Goede wrote:
> This is a preparation patch for adding a number of WARN_CONSOLE_UNLOCKED()
> calls to the fbcon code, which may be built as a module (event though
> usually it is not).
> 
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> ---
> Changes in v3:
> -New patch in v3 of this patchset
> ---
>   kernel/printk/printk.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index 247808333ba4..3f041e7cbfc9 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -2243,6 +2243,7 @@ int is_console_locked(void)
>   {
>   	return console_locked;
>   }
> +EXPORT_SYMBOL(is_console_locked);
>   
>   /*
>    * Check if we have any console that is capable of printing while cpu is
> 

Re: [PATCH v4 0/3] console/fbcon: Add support for deferred console takeover

[Steven Rostedt]

On Tue, 26 Jun 2018 20:36:09 +0200
Hans de Goede <hdegoede@redhat.com> wrote:

> Hi All,
> 
> Here is v4 of my patch-set, to delay fbcon taking over the console (and
> binding to fbdev devices) until there actually is some text output to the
> console. This is intended for use with the "quiet" cmdline option, in
> combination with a bootloader which leaves the vendor's logo /
> EFI bootgraphics put up by the firmware intact on the EFI framebuffer.
> 
> The end goal here is a boot where the firmware shows its boot graphics
> and these stay in place for a couple of seconds until the GUI loads and
> the GUI then smoothly takes over the framebuffer without any distruptions.
> 
> This patch-set spans 2 subsystems.
> 
> Petr, the printk subsys change is really trivial (1 line addition) can we
> get your Acked-by for merging all 3 patches through the fbdev tree?
> 
> Changelog:
> 
> Changes in v4:
> -Keep the comments about which fbcon functions need locks in place
> 

For 1 and 2:

Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

I'll let others handle patch 3.

-- Steve

Re: [PATCH v3 1/3] printk: Export is_console_locked

[Sergey Senozhatsky]

On (06/26/18 20:36), Hans de Goede wrote:
> This is a preparation patch for adding a number of WARN_CONSOLE_UNLOCKED()
> calls to the fbcon code, which may be built as a module (event though
> usually it is not).
> 
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>

	-ss

Re: [PATCH v3 2/3] fbcon: Call WARN_CONSOLE_UNLOCKED() where applicable

[Sergey Senozhatsky]

On (06/26/18 20:36), Hans de Goede wrote:
> Replace comments about places where the console lock should be held with
> calls to WARN_CONSOLE_UNLOCKED() to assert that it is actually held.
> 
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>

	-ss

Re: [PATCH v4 0/3] console/fbcon: Add support for deferred console takeover

[Daniel Vetter]

On Tue, Jun 26, 2018 at 08:36:09PM +0200, Hans de Goede wrote:
> Hi All,
> 
> Here is v4 of my patch-set, to delay fbcon taking over the console (and
> binding to fbdev devices) until there actually is some text output to the
> console. This is intended for use with the "quiet" cmdline option, in
> combination with a bootloader which leaves the vendor's logo /
> EFI bootgraphics put up by the firmware intact on the EFI framebuffer.
> 
> The end goal here is a boot where the firmware shows its boot graphics
> and these stay in place for a couple of seconds until the GUI loads and
> the GUI then smoothly takes over the framebuffer without any distruptions.
> 
> This patch-set spans 2 subsystems.
> 
> Petr, the printk subsys change is really trivial (1 line addition) can we
> get your Acked-by for merging all 3 patches through the fbdev tree?
> 
> Changelog:
> 
> Changes in v4:
> -Keep the comments about which fbcon functions need locks in place
> 
> Changes in v3:
> -Export is_console_locke() for use in modules (as fbcon may be built as a .ko)
> -Use WARN_CONSOLE_UNLOCKED() in several places in the fbcon code to assert
>  proper locking (requested by Daniel)
> -Unregister the fbcon-dummycon-output-notifier on fbcon_exit() (req. by Daniel)
> -Document the fbcon=nodefer commandline option (req. by Emil)
> 
> Changes in v2:
> -Check the whole string when checking for erases in putcs, instead of just
>  the first char
> -Make dummycon_blank return 1, so that a redraw gets triggered and any text
>  rendered while blanked gets output so that it can trigger a deferred
>  takeover if one is pending

Wrt merging I think it'd be best if we stuff this into drm-misc-next -
that will increase testing by gpu drivers a lot, instead of a suprise when
the fbdev pull lands in upstream.

Bart, is that ok with you?

Hans, if Bart acks this you can directly push this imo.
-Daniel

> 
> Regards,
> 
> Hans
>  
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

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

Re: [PATCH v4 0/3] console/fbcon: Add support for deferred console takeover

[Bartlomiej Zolnierkiewicz]

On Wednesday, June 27, 2018 11:15:20 AM Daniel Vetter wrote:
> On Tue, Jun 26, 2018 at 08:36:09PM +0200, Hans de Goede wrote:
> > Hi All,
> > 
> > Here is v4 of my patch-set, to delay fbcon taking over the console (and
> > binding to fbdev devices) until there actually is some text output to the
> > console. This is intended for use with the "quiet" cmdline option, in
> > combination with a bootloader which leaves the vendor's logo /
> > EFI bootgraphics put up by the firmware intact on the EFI framebuffer.
> > 
> > The end goal here is a boot where the firmware shows its boot graphics
> > and these stay in place for a couple of seconds until the GUI loads and
> > the GUI then smoothly takes over the framebuffer without any distruptions.
> > 
> > This patch-set spans 2 subsystems.
> > 
> > Petr, the printk subsys change is really trivial (1 line addition) can we
> > get your Acked-by for merging all 3 patches through the fbdev tree?
> > 
> > Changelog:
> > 
> > Changes in v4:
> > -Keep the comments about which fbcon functions need locks in place
> > 
> > Changes in v3:
> > -Export is_console_locke() for use in modules (as fbcon may be built as a .ko)
> > -Use WARN_CONSOLE_UNLOCKED() in several places in the fbcon code to assert
> >  proper locking (requested by Daniel)
> > -Unregister the fbcon-dummycon-output-notifier on fbcon_exit() (req. by Daniel)
> > -Document the fbcon=nodefer commandline option (req. by Emil)
> > 
> > Changes in v2:
> > -Check the whole string when checking for erases in putcs, instead of just
> >  the first char
> > -Make dummycon_blank return 1, so that a redraw gets triggered and any text
> >  rendered while blanked gets output so that it can trigger a deferred
> >  takeover if one is pending
> 
> Wrt merging I think it'd be best if we stuff this into drm-misc-next -
> that will increase testing by gpu drivers a lot, instead of a suprise when
> the fbdev pull lands in upstream.
> 
> Bart, is that ok with you?

Not really, since there are efifb changes in the queue which depend
on this series I would really prefer to merge all patches through
fbdev tree.

Also fbdev tree is pulled into -next kernels so testing coverage
should be okay (I assume that everybody are testing -next kernels in
addition to their own branches :-)..

> Hans, if Bart acks this you can directly push this imo.
> -Daniel

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics

Re: [PATCH v4 0/3] console/fbcon: Add support for deferred console takeover

[Hans de Goede]

Hi,

On 27-06-18 11:47, Bartlomiej Zolnierkiewicz wrote:
> On Wednesday, June 27, 2018 11:15:20 AM Daniel Vetter wrote:
>> On Tue, Jun 26, 2018 at 08:36:09PM +0200, Hans de Goede wrote:
>>> Hi All,
>>>
>>> Here is v4 of my patch-set, to delay fbcon taking over the console (and
>>> binding to fbdev devices) until there actually is some text output to the
>>> console. This is intended for use with the "quiet" cmdline option, in
>>> combination with a bootloader which leaves the vendor's logo /
>>> EFI bootgraphics put up by the firmware intact on the EFI framebuffer.
>>>
>>> The end goal here is a boot where the firmware shows its boot graphics
>>> and these stay in place for a couple of seconds until the GUI loads and
>>> the GUI then smoothly takes over the framebuffer without any distruptions.
>>>
>>> This patch-set spans 2 subsystems.
>>>
>>> Petr, the printk subsys change is really trivial (1 line addition) can we
>>> get your Acked-by for merging all 3 patches through the fbdev tree?
>>>
>>> Changelog:
>>>
>>> Changes in v4:
>>> -Keep the comments about which fbcon functions need locks in place
>>>
>>> Changes in v3:
>>> -Export is_console_locke() for use in modules (as fbcon may be built as a .ko)
>>> -Use WARN_CONSOLE_UNLOCKED() in several places in the fbcon code to assert
>>>   proper locking (requested by Daniel)
>>> -Unregister the fbcon-dummycon-output-notifier on fbcon_exit() (req. by Daniel)
>>> -Document the fbcon=nodefer commandline option (req. by Emil)
>>>
>>> Changes in v2:
>>> -Check the whole string when checking for erases in putcs, instead of just
>>>   the first char
>>> -Make dummycon_blank return 1, so that a redraw gets triggered and any text
>>>   rendered while blanked gets output so that it can trigger a deferred
>>>   takeover if one is pending
>>
>> Wrt merging I think it'd be best if we stuff this into drm-misc-next -
>> that will increase testing by gpu drivers a lot, instead of a suprise when
>> the fbdev pull lands in upstream.
>>
>> Bart, is that ok with you?
> 
> Not really, since there are efifb changes in the queue which depend
> on this series I would really prefer to merge all patches through
> fbdev tree.
> 
> Also fbdev tree is pulled into -next kernels so testing coverage
> should be okay (I assume that everybody are testing -next kernels in
> addition to their own branches :-)..

If you are talking about the "efifb: Copy the ACPI BGRT boot graphics to the
framebuffer" series, I could push those to drm-misc-next too (once acked).

I think most GPU driver developers are running drm-tip and not
-next, so putting things in drm-misc-next would give the changes somewhat
more test-exposure on a wider range of GPUs I believe. Where as -next
testing will likely be more server use-case oriented.

Alternatively you could merge things in the fbdev tree, do an
unmutable branch and then that could be merged into drm-misc-next by
the drm-misc-next maintainers.

Note either way is fine with me. This is up to you and Daniel.

Regards,

Hans

Re: [PATCH v3 1/3] printk: Export is_console_locked

[Petr Mladek]

On Tue 2018-06-26 20:36:10, Hans de Goede wrote:
> This is a preparation patch for adding a number of WARN_CONSOLE_UNLOCKED()
> calls to the fbcon code, which may be built as a module (event though
> usually it is not).
> 
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Acked-by: Petr Mladek <pmladek@suse.com>

Best Regards,
Petr

Re: [PATCH v4 0/3] console/fbcon: Add support for deferred console takeover

[Daniel Vetter]

On Wed, Jun 27, 2018 at 1:13 PM, Hans de Goede <hdegoede@redhat.com> wrote:
> Hi,
>
>
> On 27-06-18 11:47, Bartlomiej Zolnierkiewicz wrote:
>>
>> On Wednesday, June 27, 2018 11:15:20 AM Daniel Vetter wrote:
>>>
>>> On Tue, Jun 26, 2018 at 08:36:09PM +0200, Hans de Goede wrote:
>>>>
>>>> Hi All,
>>>>
>>>> Here is v4 of my patch-set, to delay fbcon taking over the console (and
>>>> binding to fbdev devices) until there actually is some text output to
>>>> the
>>>> console. This is intended for use with the "quiet" cmdline option, in
>>>> combination with a bootloader which leaves the vendor's logo /
>>>> EFI bootgraphics put up by the firmware intact on the EFI framebuffer.
>>>>
>>>> The end goal here is a boot where the firmware shows its boot graphics
>>>> and these stay in place for a couple of seconds until the GUI loads and
>>>> the GUI then smoothly takes over the framebuffer without any
>>>> distruptions.
>>>>
>>>> This patch-set spans 2 subsystems.
>>>>
>>>> Petr, the printk subsys change is really trivial (1 line addition) can
>>>> we
>>>> get your Acked-by for merging all 3 patches through the fbdev tree?
>>>>
>>>> Changelog:
>>>>
>>>> Changes in v4:
>>>> -Keep the comments about which fbcon functions need locks in place
>>>>
>>>> Changes in v3:
>>>> -Export is_console_locke() for use in modules (as fbcon may be built as
>>>> a .ko)
>>>> -Use WARN_CONSOLE_UNLOCKED() in several places in the fbcon code to
>>>> assert
>>>>   proper locking (requested by Daniel)
>>>> -Unregister the fbcon-dummycon-output-notifier on fbcon_exit() (req. by
>>>> Daniel)
>>>> -Document the fbcon=nodefer commandline option (req. by Emil)
>>>>
>>>> Changes in v2:
>>>> -Check the whole string when checking for erases in putcs, instead of
>>>> just
>>>>   the first char
>>>> -Make dummycon_blank return 1, so that a redraw gets triggered and any
>>>> text
>>>>   rendered while blanked gets output so that it can trigger a deferred
>>>>   takeover if one is pending
>>>
>>>
>>> Wrt merging I think it'd be best if we stuff this into drm-misc-next -
>>> that will increase testing by gpu drivers a lot, instead of a suprise
>>> when
>>> the fbdev pull lands in upstream.
>>>
>>> Bart, is that ok with you?
>>
>>
>> Not really, since there are efifb changes in the queue which depend
>> on this series I would really prefer to merge all patches through
>> fbdev tree.
>>
>> Also fbdev tree is pulled into -next kernels so testing coverage
>> should be okay (I assume that everybody are testing -next kernels in
>> addition to their own branches :-)..

Ime this is a rather unrealistic assumption ...

> If you are talking about the "efifb: Copy the ACPI BGRT boot graphics to the
> framebuffer" series, I could push those to drm-misc-next too (once acked).
>
> I think most GPU driver developers are running drm-tip and not
> -next, so putting things in drm-misc-next would give the changes somewhat
> more test-exposure on a wider range of GPUs I believe. Where as -next
> testing will likely be more server use-case oriented.
>
> Alternatively you could merge things in the fbdev tree, do an
> unmutable branch and then that could be merged into drm-misc-next by
> the drm-misc-next maintainers.
>
> Note either way is fine with me. This is up to you and Daniel.

Yeah pull request for a topic branch works too.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

Re: [PATCH v3 3/3] console/fbcon: Add support for deferred console takeover

[Daniel Vetter]

On Tue, Jun 26, 2018 at 08:36:12PM +0200, Hans de Goede wrote:
> Currently fbcon claims fbdevs as soon as they are registered and takes over
> the console as soon as the first fbdev gets registered.
> 
> This behavior is undesirable in cases where a smooth graphical bootup is
> desired, in such cases we typically want the contents of the framebuffer
> (typically a vendor logo) to stay in place as is.
> 
> The current solution for this problem (on embedded systems) is to not
> enable fbcon.
> 
> This commit adds a new FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER config option,
> which when enabled defers fbcon taking over the console from the dummy
> console until the first text is displayed on the console. Together with the
> "quiet" kernel commandline option, this allows fbcon to still be used
> together with a smooth graphical bootup, having it take over the console as
> soon as e.g. an error message is logged.
> 
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>

A bit a late comment, and feel free to reject: Have you considered
registering the fbcon driver, but not doing any modesets until the very
first real message shows up?

That would make it work with any console driver setup, even when dummy
console is deactivated. And it would avoid the notifier layering
violation, which still irks me a bit with this approach here.
-Daniel

> ---
> Changes in v2:
> -Check the whole string when checking for erases in putcs, instead of just
>  the first char
> -Make dummycon_blank return 1, so that a redraw gets triggered and any text
>  rendered while blanked gets output so that it can trigger a deferred
>  takeover if one is pending
> 
> Changes in v3:
> -Call WARN_CONSOLE_UNLOCKED() from fbcon_output_notifier()
> -Unregister the notifier on fbcon_exit()
> -Document the fbcon=nodefer commandline option in Documentation/fb/fbcon.txt
> ---
>  Documentation/fb/fbcon.txt       |  7 ++++
>  drivers/video/console/Kconfig    | 11 +++++
>  drivers/video/console/dummycon.c | 67 +++++++++++++++++++++++++----
>  drivers/video/fbdev/core/fbcon.c | 72 ++++++++++++++++++++++++++++++++
>  include/linux/console.h          |  5 +++
>  5 files changed, 154 insertions(+), 8 deletions(-)
> 
> diff --git a/Documentation/fb/fbcon.txt b/Documentation/fb/fbcon.txt
> index 79c22d096bbc..d4d642e1ce9c 100644
> --- a/Documentation/fb/fbcon.txt
> +++ b/Documentation/fb/fbcon.txt
> @@ -155,6 +155,13 @@ C. Boot options
>  	used by text. By default, this area will be black. The 'color' value
>  	is an integer number that depends on the framebuffer driver being used.
>  
> +6. fbcon=nodefer
> +
> +	If the kernel is compiled with deferred fbcon takeover support, normally
> +	the framebuffer contents, left in place by the firmware/bootloader, will
> +	be preserved until there actually is some text is output to the console.
> +	This option causes fbcon to bind immediately to the fbdev device.
> +
>  C. Attaching, Detaching and Unloading
>  
>  Before going on how to attach, detach and unload the framebuffer console, an
> diff --git a/drivers/video/console/Kconfig b/drivers/video/console/Kconfig
> index 4110ba7d7ca9..e91edef98633 100644
> --- a/drivers/video/console/Kconfig
> +++ b/drivers/video/console/Kconfig
> @@ -150,6 +150,17 @@ config FRAMEBUFFER_CONSOLE_ROTATION
>           such that other users of the framebuffer will remain normally
>           oriented.
>  
> +config FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
> +	bool "Framebuffer Console Deferred Takeover"
> +	depends on FRAMEBUFFER_CONSOLE=y && DUMMY_CONSOLE=y
> +	help
> +	  If enabled this defers the framebuffer console taking over the
> +	  console from the dummy console until the first text is displayed on
> +	  the console. This is useful in combination with the "quiet" kernel
> +	  commandline option to keep the framebuffer contents initially put up
> +	  by the firmware in place, rather then replacing the contents with a
> +	  black screen as soon as fbcon loads.
> +
>  config STI_CONSOLE
>          bool "STI text console"
>  	depends on PARISC && HAS_IOMEM
> diff --git a/drivers/video/console/dummycon.c b/drivers/video/console/dummycon.c
> index f2eafe2ed980..45ad925ad5f8 100644
> --- a/drivers/video/console/dummycon.c
> +++ b/drivers/video/console/dummycon.c
> @@ -26,6 +26,65 @@
>  #define DUMMY_ROWS	CONFIG_DUMMY_CONSOLE_ROWS
>  #endif
>  
> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
> +/* These are both protected by the console_lock */
> +static RAW_NOTIFIER_HEAD(dummycon_output_nh);
> +static bool dummycon_putc_called;
> +
> +void dummycon_register_output_notifier(struct notifier_block *nb)
> +{
> +	raw_notifier_chain_register(&dummycon_output_nh, nb);
> +
> +	if (dummycon_putc_called)
> +		nb->notifier_call(nb, 0, NULL);
> +}
> +
> +void dummycon_unregister_output_notifier(struct notifier_block *nb)
> +{
> +	raw_notifier_chain_unregister(&dummycon_output_nh, nb);
> +}
> +
> +static void dummycon_putc(struct vc_data *vc, int c, int ypos, int xpos)
> +{
> +	dummycon_putc_called = true;
> +	raw_notifier_call_chain(&dummycon_output_nh, 0, NULL);
> +}
> +
> +static void dummycon_putcs(struct vc_data *vc, const unsigned short *s,
> +			   int count, int ypos, int xpos)
> +{
> +	int i;
> +
> +	if (!dummycon_putc_called) {
> +		/* Ignore erases */
> +		for (i = 0 ; i < count; i++) {
> +			if (s[i] != vc->vc_video_erase_char)
> +				break;
> +		}
> +		if (i == count)
> +			return;
> +
> +		dummycon_putc_called = true;
> +	}
> +
> +	raw_notifier_call_chain(&dummycon_output_nh, 0, NULL);
> +}
> +
> +static int dummycon_blank(struct vc_data *vc, int blank, int mode_switch)
> +{
> +	/* Redraw, so that we get putc(s) for output done while blanked */
> +	return 1;
> +}
> +#else
> +static void dummycon_putc(struct vc_data *vc, int c, int ypos, int xpos) { }
> +static void dummycon_putcs(struct vc_data *vc, const unsigned short *s,
> +			   int count, int ypos, int xpos) { }
> +static int dummycon_blank(struct vc_data *vc, int blank, int mode_switch)
> +{
> +	return 0;
> +}
> +#endif
> +
>  static const char *dummycon_startup(void)
>  {
>      return "dummy device";
> @@ -44,9 +103,6 @@ static void dummycon_init(struct vc_data *vc, int init)
>  static void dummycon_deinit(struct vc_data *vc) { }
>  static void dummycon_clear(struct vc_data *vc, int sy, int sx, int height,
>  			   int width) { }
> -static void dummycon_putc(struct vc_data *vc, int c, int ypos, int xpos) { }
> -static void dummycon_putcs(struct vc_data *vc, const unsigned short *s,
> -			   int count, int ypos, int xpos) { }
>  static void dummycon_cursor(struct vc_data *vc, int mode) { }
>  
>  static bool dummycon_scroll(struct vc_data *vc, unsigned int top,
> @@ -61,11 +117,6 @@ static int dummycon_switch(struct vc_data *vc)
>  	return 0;
>  }
>  
> -static int dummycon_blank(struct vc_data *vc, int blank, int mode_switch)
> -{
> -	return 0;
> -}
> -
>  static int dummycon_font_set(struct vc_data *vc, struct console_font *font,
>  			     unsigned int flags)
>  {
> diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
> index cd8d52a967aa..5fb156bdcf4e 100644
> --- a/drivers/video/fbdev/core/fbcon.c
> +++ b/drivers/video/fbdev/core/fbcon.c
> @@ -129,6 +129,12 @@ static inline void fbcon_map_override(void)
>  }
>  #endif /* CONFIG_FRAMEBUFFER_CONSOLE_DETECT_PRIMARY */
>  
> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
> +static bool deferred_takeover = true;
> +#else
> +#define deferred_takeover false
> +#endif
> +
>  /* font data */
>  static char fontname[40];
>  
> @@ -499,6 +505,12 @@ static int __init fb_console_setup(char *this_opt)
>  				margin_color = simple_strtoul(options, &options, 0);
>  			continue;
>  		}
> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
> +		if (!strcmp(options, "nodefer")) {
> +			deferred_takeover = false;
> +			continue;
> +		}
> +#endif
>  	}
>  	return 1;
>  }
> @@ -3100,6 +3112,9 @@ static int fbcon_fb_unregistered(struct fb_info *info)
>  
>  	WARN_CONSOLE_UNLOCKED();
>  
> +	if (deferred_takeover)
> +		return 0;
> +
>  	idx = info->node;
>  	for (i = first_fb_vc; i <= last_fb_vc; i++) {
>  		if (con2fb_map[i] == idx)
> @@ -3140,6 +3155,13 @@ static void fbcon_remap_all(int idx)
>  
>  	WARN_CONSOLE_UNLOCKED();
>  
> +	if (deferred_takeover) {
> +		for (i = first_fb_vc; i <= last_fb_vc; i++)
> +			con2fb_map_boot[i] = idx;
> +		fbcon_map_override();
> +		return;
> +	}
> +
>  	for (i = first_fb_vc; i <= last_fb_vc; i++)
>  		set_con2fb_map(i, idx, 0);
>  
> @@ -3191,6 +3213,11 @@ static int fbcon_fb_registered(struct fb_info *info)
>  	idx = info->node;
>  	fbcon_select_primary(info);
>  
> +	if (deferred_takeover) {
> +		pr_info("fbcon: Deferring console take-over\n");
> +		return 0;
> +	}
> +
>  	if (info_idx == -1) {
>  		for (i = first_fb_vc; i <= last_fb_vc; i++) {
>  			if (con2fb_map_boot[i] == idx) {
> @@ -3566,8 +3593,46 @@ static int fbcon_init_device(void)
>  	return 0;
>  }
>  
> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
> +static struct notifier_block fbcon_output_nb;
> +
> +static int fbcon_output_notifier(struct notifier_block *nb,
> +				 unsigned long action, void *data)
> +{
> +	int i;
> +
> +	WARN_CONSOLE_UNLOCKED();
> +
> +	pr_info("fbcon: Taking over console\n");
> +
> +	dummycon_unregister_output_notifier(&fbcon_output_nb);
> +	deferred_takeover = false;
> +	logo_shown = FBCON_LOGO_DONTSHOW;
> +
> +	for (i = 0; i < FB_MAX; i++) {
> +		if (registered_fb[i])
> +			fbcon_fb_registered(registered_fb[i]);
> +	}
> +
> +	return NOTIFY_OK;
> +}
> +
> +static void fbcon_register_output_notifier(void)
> +{
> +	fbcon_output_nb.notifier_call = fbcon_output_notifier;
> +	dummycon_register_output_notifier(&fbcon_output_nb);
> +}
> +#else
> +static inline void fbcon_register_output_notifier(void) {}
> +#endif
> +
>  static void fbcon_start(void)
>  {
> +	if (deferred_takeover) {
> +		fbcon_register_output_notifier();
> +		return;
> +	}
> +
>  	if (num_registered_fb) {
>  		int i;
>  
> @@ -3594,6 +3659,13 @@ static void fbcon_exit(void)
>  	if (fbcon_has_exited)
>  		return;
>  
> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
> +	if (deferred_takeover) {
> +		dummycon_unregister_output_notifier(&fbcon_output_nb);
> +		deferred_takeover = false;
> +	}
> +#endif
> +
>  	kfree((void *)softback_buf);
>  	softback_buf = 0UL;
>  
> diff --git a/include/linux/console.h b/include/linux/console.h
> index dfd6b0e97855..f59f3dbca65c 100644
> --- a/include/linux/console.h
> +++ b/include/linux/console.h
> @@ -21,6 +21,7 @@ struct console_font_op;
>  struct console_font;
>  struct module;
>  struct tty_struct;
> +struct notifier_block;
>  
>  /*
>   * this is what the terminal answers to a ESC-Z or csi0c query.
> @@ -220,4 +221,8 @@ static inline bool vgacon_text_force(void) { return false; }
>  
>  extern void console_init(void);
>  
> +/* For deferred console takeover */
> +void dummycon_register_output_notifier(struct notifier_block *nb);
> +void dummycon_unregister_output_notifier(struct notifier_block *nb);
> +
>  #endif /* _LINUX_CONSOLE_H */
> -- 
> 2.17.1
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

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

Re: [PATCH v3 3/3] console/fbcon: Add support for deferred console takeover

[Hans de Goede]

Hi,

On 28-06-18 09:55, Daniel Vetter wrote:
> On Tue, Jun 26, 2018 at 08:36:12PM +0200, Hans de Goede wrote:
>> Currently fbcon claims fbdevs as soon as they are registered and takes over
>> the console as soon as the first fbdev gets registered.
>>
>> This behavior is undesirable in cases where a smooth graphical bootup is
>> desired, in such cases we typically want the contents of the framebuffer
>> (typically a vendor logo) to stay in place as is.
>>
>> The current solution for this problem (on embedded systems) is to not
>> enable fbcon.
>>
>> This commit adds a new FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER config option,
>> which when enabled defers fbcon taking over the console from the dummy
>> console until the first text is displayed on the console. Together with the
>> "quiet" kernel commandline option, this allows fbcon to still be used
>> together with a smooth graphical bootup, having it take over the console as
>> soon as e.g. an error message is logged.
>>
>> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> 
> A bit a late comment, and feel free to reject: Have you considered
> registering the fbcon driver, but not doing any modesets until the very
> first real message shows up?

I have tried something like that, but it did not work out, this patch-set
actually is my 3th attempt at this (the other 2 were never posted
because they did not work).

The fbcon code is woven quite tightly into the console code, so this was
the only clean way I could find to achieve what I want.

Regards,

Hans


>> ---
>> Changes in v2:
>> -Check the whole string when checking for erases in putcs, instead of just
>>   the first char
>> -Make dummycon_blank return 1, so that a redraw gets triggered and any text
>>   rendered while blanked gets output so that it can trigger a deferred
>>   takeover if one is pending
>>
>> Changes in v3:
>> -Call WARN_CONSOLE_UNLOCKED() from fbcon_output_notifier()
>> -Unregister the notifier on fbcon_exit()
>> -Document the fbcon=nodefer commandline option in Documentation/fb/fbcon.txt
>> ---
>>   Documentation/fb/fbcon.txt       |  7 ++++
>>   drivers/video/console/Kconfig    | 11 +++++
>>   drivers/video/console/dummycon.c | 67 +++++++++++++++++++++++++----
>>   drivers/video/fbdev/core/fbcon.c | 72 ++++++++++++++++++++++++++++++++
>>   include/linux/console.h          |  5 +++
>>   5 files changed, 154 insertions(+), 8 deletions(-)
>>
>> diff --git a/Documentation/fb/fbcon.txt b/Documentation/fb/fbcon.txt
>> index 79c22d096bbc..d4d642e1ce9c 100644
>> --- a/Documentation/fb/fbcon.txt
>> +++ b/Documentation/fb/fbcon.txt
>> @@ -155,6 +155,13 @@ C. Boot options
>>   	used by text. By default, this area will be black. The 'color' value
>>   	is an integer number that depends on the framebuffer driver being used.
>>   
>> +6. fbcon=nodefer
>> +
>> +	If the kernel is compiled with deferred fbcon takeover support, normally
>> +	the framebuffer contents, left in place by the firmware/bootloader, will
>> +	be preserved until there actually is some text is output to the console.
>> +	This option causes fbcon to bind immediately to the fbdev device.
>> +
>>   C. Attaching, Detaching and Unloading
>>   
>>   Before going on how to attach, detach and unload the framebuffer console, an
>> diff --git a/drivers/video/console/Kconfig b/drivers/video/console/Kconfig
>> index 4110ba7d7ca9..e91edef98633 100644
>> --- a/drivers/video/console/Kconfig
>> +++ b/drivers/video/console/Kconfig
>> @@ -150,6 +150,17 @@ config FRAMEBUFFER_CONSOLE_ROTATION
>>            such that other users of the framebuffer will remain normally
>>            oriented.
>>   
>> +config FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
>> +	bool "Framebuffer Console Deferred Takeover"
>> +	depends on FRAMEBUFFER_CONSOLE=y && DUMMY_CONSOLE=y
>> +	help
>> +	  If enabled this defers the framebuffer console taking over the
>> +	  console from the dummy console until the first text is displayed on
>> +	  the console. This is useful in combination with the "quiet" kernel
>> +	  commandline option to keep the framebuffer contents initially put up
>> +	  by the firmware in place, rather then replacing the contents with a
>> +	  black screen as soon as fbcon loads.
>> +
>>   config STI_CONSOLE
>>           bool "STI text console"
>>   	depends on PARISC && HAS_IOMEM
>> diff --git a/drivers/video/console/dummycon.c b/drivers/video/console/dummycon.c
>> index f2eafe2ed980..45ad925ad5f8 100644
>> --- a/drivers/video/console/dummycon.c
>> +++ b/drivers/video/console/dummycon.c
>> @@ -26,6 +26,65 @@
>>   #define DUMMY_ROWS	CONFIG_DUMMY_CONSOLE_ROWS
>>   #endif
>>   
>> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
>> +/* These are both protected by the console_lock */
>> +static RAW_NOTIFIER_HEAD(dummycon_output_nh);
>> +static bool dummycon_putc_called;
>> +
>> +void dummycon_register_output_notifier(struct notifier_block *nb)
>> +{
>> +	raw_notifier_chain_register(&dummycon_output_nh, nb);
>> +
>> +	if (dummycon_putc_called)
>> +		nb->notifier_call(nb, 0, NULL);
>> +}
>> +
>> +void dummycon_unregister_output_notifier(struct notifier_block *nb)
>> +{
>> +	raw_notifier_chain_unregister(&dummycon_output_nh, nb);
>> +}
>> +
>> +static void dummycon_putc(struct vc_data *vc, int c, int ypos, int xpos)
>> +{
>> +	dummycon_putc_called = true;
>> +	raw_notifier_call_chain(&dummycon_output_nh, 0, NULL);
>> +}
>> +
>> +static void dummycon_putcs(struct vc_data *vc, const unsigned short *s,
>> +			   int count, int ypos, int xpos)
>> +{
>> +	int i;
>> +
>> +	if (!dummycon_putc_called) {
>> +		/* Ignore erases */
>> +		for (i = 0 ; i < count; i++) {
>> +			if (s[i] != vc->vc_video_erase_char)
>> +				break;
>> +		}
>> +		if (i == count)
>> +			return;
>> +
>> +		dummycon_putc_called = true;
>> +	}
>> +
>> +	raw_notifier_call_chain(&dummycon_output_nh, 0, NULL);
>> +}
>> +
>> +static int dummycon_blank(struct vc_data *vc, int blank, int mode_switch)
>> +{
>> +	/* Redraw, so that we get putc(s) for output done while blanked */
>> +	return 1;
>> +}
>> +#else
>> +static void dummycon_putc(struct vc_data *vc, int c, int ypos, int xpos) { }
>> +static void dummycon_putcs(struct vc_data *vc, const unsigned short *s,
>> +			   int count, int ypos, int xpos) { }
>> +static int dummycon_blank(struct vc_data *vc, int blank, int mode_switch)
>> +{
>> +	return 0;
>> +}
>> +#endif
>> +
>>   static const char *dummycon_startup(void)
>>   {
>>       return "dummy device";
>> @@ -44,9 +103,6 @@ static void dummycon_init(struct vc_data *vc, int init)
>>   static void dummycon_deinit(struct vc_data *vc) { }
>>   static void dummycon_clear(struct vc_data *vc, int sy, int sx, int height,
>>   			   int width) { }
>> -static void dummycon_putc(struct vc_data *vc, int c, int ypos, int xpos) { }
>> -static void dummycon_putcs(struct vc_data *vc, const unsigned short *s,
>> -			   int count, int ypos, int xpos) { }
>>   static void dummycon_cursor(struct vc_data *vc, int mode) { }
>>   
>>   static bool dummycon_scroll(struct vc_data *vc, unsigned int top,
>> @@ -61,11 +117,6 @@ static int dummycon_switch(struct vc_data *vc)
>>   	return 0;
>>   }
>>   
>> -static int dummycon_blank(struct vc_data *vc, int blank, int mode_switch)
>> -{
>> -	return 0;
>> -}
>> -
>>   static int dummycon_font_set(struct vc_data *vc, struct console_font *font,
>>   			     unsigned int flags)
>>   {
>> diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
>> index cd8d52a967aa..5fb156bdcf4e 100644
>> --- a/drivers/video/fbdev/core/fbcon.c
>> +++ b/drivers/video/fbdev/core/fbcon.c
>> @@ -129,6 +129,12 @@ static inline void fbcon_map_override(void)
>>   }
>>   #endif /* CONFIG_FRAMEBUFFER_CONSOLE_DETECT_PRIMARY */
>>   
>> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
>> +static bool deferred_takeover = true;
>> +#else
>> +#define deferred_takeover false
>> +#endif
>> +
>>   /* font data */
>>   static char fontname[40];
>>   
>> @@ -499,6 +505,12 @@ static int __init fb_console_setup(char *this_opt)
>>   				margin_color = simple_strtoul(options, &options, 0);
>>   			continue;
>>   		}
>> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
>> +		if (!strcmp(options, "nodefer")) {
>> +			deferred_takeover = false;
>> +			continue;
>> +		}
>> +#endif
>>   	}
>>   	return 1;
>>   }
>> @@ -3100,6 +3112,9 @@ static int fbcon_fb_unregistered(struct fb_info *info)
>>   
>>   	WARN_CONSOLE_UNLOCKED();
>>   
>> +	if (deferred_takeover)
>> +		return 0;
>> +
>>   	idx = info->node;
>>   	for (i = first_fb_vc; i <= last_fb_vc; i++) {
>>   		if (con2fb_map[i] == idx)
>> @@ -3140,6 +3155,13 @@ static void fbcon_remap_all(int idx)
>>   
>>   	WARN_CONSOLE_UNLOCKED();
>>   
>> +	if (deferred_takeover) {
>> +		for (i = first_fb_vc; i <= last_fb_vc; i++)
>> +			con2fb_map_boot[i] = idx;
>> +		fbcon_map_override();
>> +		return;
>> +	}
>> +
>>   	for (i = first_fb_vc; i <= last_fb_vc; i++)
>>   		set_con2fb_map(i, idx, 0);
>>   
>> @@ -3191,6 +3213,11 @@ static int fbcon_fb_registered(struct fb_info *info)
>>   	idx = info->node;
>>   	fbcon_select_primary(info);
>>   
>> +	if (deferred_takeover) {
>> +		pr_info("fbcon: Deferring console take-over\n");
>> +		return 0;
>> +	}
>> +
>>   	if (info_idx == -1) {
>>   		for (i = first_fb_vc; i <= last_fb_vc; i++) {
>>   			if (con2fb_map_boot[i] == idx) {
>> @@ -3566,8 +3593,46 @@ static int fbcon_init_device(void)
>>   	return 0;
>>   }
>>   
>> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
>> +static struct notifier_block fbcon_output_nb;
>> +
>> +static int fbcon_output_notifier(struct notifier_block *nb,
>> +				 unsigned long action, void *data)
>> +{
>> +	int i;
>> +
>> +	WARN_CONSOLE_UNLOCKED();
>> +
>> +	pr_info("fbcon: Taking over console\n");
>> +
>> +	dummycon_unregister_output_notifier(&fbcon_output_nb);
>> +	deferred_takeover = false;
>> +	logo_shown = FBCON_LOGO_DONTSHOW;
>> +
>> +	for (i = 0; i < FB_MAX; i++) {
>> +		if (registered_fb[i])
>> +			fbcon_fb_registered(registered_fb[i]);
>> +	}
>> +
>> +	return NOTIFY_OK;
>> +}
>> +
>> +static void fbcon_register_output_notifier(void)
>> +{
>> +	fbcon_output_nb.notifier_call = fbcon_output_notifier;
>> +	dummycon_register_output_notifier(&fbcon_output_nb);
>> +}
>> +#else
>> +static inline void fbcon_register_output_notifier(void) {}
>> +#endif
>> +
>>   static void fbcon_start(void)
>>   {
>> +	if (deferred_takeover) {
>> +		fbcon_register_output_notifier();
>> +		return;
>> +	}
>> +
>>   	if (num_registered_fb) {
>>   		int i;
>>   
>> @@ -3594,6 +3659,13 @@ static void fbcon_exit(void)
>>   	if (fbcon_has_exited)
>>   		return;
>>   
>> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
>> +	if (deferred_takeover) {
>> +		dummycon_unregister_output_notifier(&fbcon_output_nb);
>> +		deferred_takeover = false;
>> +	}
>> +#endif
>> +
>>   	kfree((void *)softback_buf);
>>   	softback_buf = 0UL;
>>   
>> diff --git a/include/linux/console.h b/include/linux/console.h
>> index dfd6b0e97855..f59f3dbca65c 100644
>> --- a/include/linux/console.h
>> +++ b/include/linux/console.h
>> @@ -21,6 +21,7 @@ struct console_font_op;
>>   struct console_font;
>>   struct module;
>>   struct tty_struct;
>> +struct notifier_block;
>>   
>>   /*
>>    * this is what the terminal answers to a ESC-Z or csi0c query.
>> @@ -220,4 +221,8 @@ static inline bool vgacon_text_force(void) { return false; }
>>   
>>   extern void console_init(void);
>>   
>> +/* For deferred console takeover */
>> +void dummycon_register_output_notifier(struct notifier_block *nb);
>> +void dummycon_unregister_output_notifier(struct notifier_block *nb);
>> +
>>   #endif /* _LINUX_CONSOLE_H */
>> -- 
>> 2.17.1
>>
>> _______________________________________________
>> dri-devel mailing list
>> dri-devel@lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
> 

Re: [PATCH v3 3/3] console/fbcon: Add support for deferred console takeover

[Daniel Vetter]

On Thu, Jun 28, 2018 at 10:20 AM, Hans de Goede <hdegoede@redhat.com> wrote:
> Hi,
>
> On 28-06-18 09:55, Daniel Vetter wrote:
>>
>> On Tue, Jun 26, 2018 at 08:36:12PM +0200, Hans de Goede wrote:
>>>
>>> Currently fbcon claims fbdevs as soon as they are registered and takes
>>> over
>>> the console as soon as the first fbdev gets registered.
>>>
>>> This behavior is undesirable in cases where a smooth graphical bootup is
>>> desired, in such cases we typically want the contents of the framebuffer
>>> (typically a vendor logo) to stay in place as is.
>>>
>>> The current solution for this problem (on embedded systems) is to not
>>> enable fbcon.
>>>
>>> This commit adds a new FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER config
>>> option,
>>> which when enabled defers fbcon taking over the console from the dummy
>>> console until the first text is displayed on the console. Together with
>>> the
>>> "quiet" kernel commandline option, this allows fbcon to still be used
>>> together with a smooth graphical bootup, having it take over the console
>>> as
>>> soon as e.g. an error message is logged.
>>>
>>> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
>>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>>
>>
>> A bit a late comment, and feel free to reject: Have you considered
>> registering the fbcon driver, but not doing any modesets until the very
>> first real message shows up?
>
>
> I have tried something like that, but it did not work out, this patch-set
> actually is my 3th attempt at this (the other 2 were never posted
> because they did not work).
>
> The fbcon code is woven quite tightly into the console code, so this was
> the only clean way I could find to achieve what I want.

I assumed/feared as much. Would be good to cover that in the commit
message, to justify your approach better.
-Daniel

>
> Regards,
>
> Hans
>
>
>
>>> ---
>>> Changes in v2:
>>> -Check the whole string when checking for erases in putcs, instead of
>>> just
>>>   the first char
>>> -Make dummycon_blank return 1, so that a redraw gets triggered and any
>>> text
>>>   rendered while blanked gets output so that it can trigger a deferred
>>>   takeover if one is pending
>>>
>>> Changes in v3:
>>> -Call WARN_CONSOLE_UNLOCKED() from fbcon_output_notifier()
>>> -Unregister the notifier on fbcon_exit()
>>> -Document the fbcon=nodefer commandline option in
>>> Documentation/fb/fbcon.txt
>>> ---
>>>   Documentation/fb/fbcon.txt       |  7 ++++
>>>   drivers/video/console/Kconfig    | 11 +++++
>>>   drivers/video/console/dummycon.c | 67 +++++++++++++++++++++++++----
>>>   drivers/video/fbdev/core/fbcon.c | 72 ++++++++++++++++++++++++++++++++
>>>   include/linux/console.h          |  5 +++
>>>   5 files changed, 154 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/Documentation/fb/fbcon.txt b/Documentation/fb/fbcon.txt
>>> index 79c22d096bbc..d4d642e1ce9c 100644
>>> --- a/Documentation/fb/fbcon.txt
>>> +++ b/Documentation/fb/fbcon.txt
>>> @@ -155,6 +155,13 @@ C. Boot options
>>>         used by text. By default, this area will be black. The 'color'
>>> value
>>>         is an integer number that depends on the framebuffer driver being
>>> used.
>>>   +6. fbcon=nodefer
>>> +
>>> +       If the kernel is compiled with deferred fbcon takeover support,
>>> normally
>>> +       the framebuffer contents, left in place by the
>>> firmware/bootloader, will
>>> +       be preserved until there actually is some text is output to the
>>> console.
>>> +       This option causes fbcon to bind immediately to the fbdev device.
>>> +
>>>   C. Attaching, Detaching and Unloading
>>>     Before going on how to attach, detach and unload the framebuffer
>>> console, an
>>> diff --git a/drivers/video/console/Kconfig
>>> b/drivers/video/console/Kconfig
>>> index 4110ba7d7ca9..e91edef98633 100644
>>> --- a/drivers/video/console/Kconfig
>>> +++ b/drivers/video/console/Kconfig
>>> @@ -150,6 +150,17 @@ config FRAMEBUFFER_CONSOLE_ROTATION
>>>            such that other users of the framebuffer will remain normally
>>>            oriented.
>>>   +config FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
>>> +       bool "Framebuffer Console Deferred Takeover"
>>> +       depends on FRAMEBUFFER_CONSOLE=y && DUMMY_CONSOLE=y
>>> +       help
>>> +         If enabled this defers the framebuffer console taking over the
>>> +         console from the dummy console until the first text is
>>> displayed on
>>> +         the console. This is useful in combination with the "quiet"
>>> kernel
>>> +         commandline option to keep the framebuffer contents initially
>>> put up
>>> +         by the firmware in place, rather then replacing the contents
>>> with a
>>> +         black screen as soon as fbcon loads.
>>> +
>>>   config STI_CONSOLE
>>>           bool "STI text console"
>>>         depends on PARISC && HAS_IOMEM
>>> diff --git a/drivers/video/console/dummycon.c
>>> b/drivers/video/console/dummycon.c
>>> index f2eafe2ed980..45ad925ad5f8 100644
>>> --- a/drivers/video/console/dummycon.c
>>> +++ b/drivers/video/console/dummycon.c
>>> @@ -26,6 +26,65 @@
>>>   #define DUMMY_ROWS    CONFIG_DUMMY_CONSOLE_ROWS
>>>   #endif
>>>   +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
>>> +/* These are both protected by the console_lock */
>>> +static RAW_NOTIFIER_HEAD(dummycon_output_nh);
>>> +static bool dummycon_putc_called;
>>> +
>>> +void dummycon_register_output_notifier(struct notifier_block *nb)
>>> +{
>>> +       raw_notifier_chain_register(&dummycon_output_nh, nb);
>>> +
>>> +       if (dummycon_putc_called)
>>> +               nb->notifier_call(nb, 0, NULL);
>>> +}
>>> +
>>> +void dummycon_unregister_output_notifier(struct notifier_block *nb)
>>> +{
>>> +       raw_notifier_chain_unregister(&dummycon_output_nh, nb);
>>> +}
>>> +
>>> +static void dummycon_putc(struct vc_data *vc, int c, int ypos, int xpos)
>>> +{
>>> +       dummycon_putc_called = true;
>>> +       raw_notifier_call_chain(&dummycon_output_nh, 0, NULL);
>>> +}
>>> +
>>> +static void dummycon_putcs(struct vc_data *vc, const unsigned short *s,
>>> +                          int count, int ypos, int xpos)
>>> +{
>>> +       int i;
>>> +
>>> +       if (!dummycon_putc_called) {
>>> +               /* Ignore erases */
>>> +               for (i = 0 ; i < count; i++) {
>>> +                       if (s[i] != vc->vc_video_erase_char)
>>> +                               break;
>>> +               }
>>> +               if (i == count)
>>> +                       return;
>>> +
>>> +               dummycon_putc_called = true;
>>> +       }
>>> +
>>> +       raw_notifier_call_chain(&dummycon_output_nh, 0, NULL);
>>> +}
>>> +
>>> +static int dummycon_blank(struct vc_data *vc, int blank, int
>>> mode_switch)
>>> +{
>>> +       /* Redraw, so that we get putc(s) for output done while blanked
>>> */
>>> +       return 1;
>>> +}
>>> +#else
>>> +static void dummycon_putc(struct vc_data *vc, int c, int ypos, int xpos)
>>> { }
>>> +static void dummycon_putcs(struct vc_data *vc, const unsigned short *s,
>>> +                          int count, int ypos, int xpos) { }
>>> +static int dummycon_blank(struct vc_data *vc, int blank, int
>>> mode_switch)
>>> +{
>>> +       return 0;
>>> +}
>>> +#endif
>>> +
>>>   static const char *dummycon_startup(void)
>>>   {
>>>       return "dummy device";
>>> @@ -44,9 +103,6 @@ static void dummycon_init(struct vc_data *vc, int
>>> init)
>>>   static void dummycon_deinit(struct vc_data *vc) { }
>>>   static void dummycon_clear(struct vc_data *vc, int sy, int sx, int
>>> height,
>>>                            int width) { }
>>> -static void dummycon_putc(struct vc_data *vc, int c, int ypos, int xpos)
>>> { }
>>> -static void dummycon_putcs(struct vc_data *vc, const unsigned short *s,
>>> -                          int count, int ypos, int xpos) { }
>>>   static void dummycon_cursor(struct vc_data *vc, int mode) { }
>>>     static bool dummycon_scroll(struct vc_data *vc, unsigned int top,
>>> @@ -61,11 +117,6 @@ static int dummycon_switch(struct vc_data *vc)
>>>         return 0;
>>>   }
>>>   -static int dummycon_blank(struct vc_data *vc, int blank, int
>>> mode_switch)
>>> -{
>>> -       return 0;
>>> -}
>>> -
>>>   static int dummycon_font_set(struct vc_data *vc, struct console_font
>>> *font,
>>>                              unsigned int flags)
>>>   {
>>> diff --git a/drivers/video/fbdev/core/fbcon.c
>>> b/drivers/video/fbdev/core/fbcon.c
>>> index cd8d52a967aa..5fb156bdcf4e 100644
>>> --- a/drivers/video/fbdev/core/fbcon.c
>>> +++ b/drivers/video/fbdev/core/fbcon.c
>>> @@ -129,6 +129,12 @@ static inline void fbcon_map_override(void)
>>>   }
>>>   #endif /* CONFIG_FRAMEBUFFER_CONSOLE_DETECT_PRIMARY */
>>>   +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
>>> +static bool deferred_takeover = true;
>>> +#else
>>> +#define deferred_takeover false
>>> +#endif
>>> +
>>>   /* font data */
>>>   static char fontname[40];
>>>   @@ -499,6 +505,12 @@ static int __init fb_console_setup(char *this_opt)
>>>                                 margin_color = simple_strtoul(options,
>>> &options, 0);
>>>                         continue;
>>>                 }
>>> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
>>> +               if (!strcmp(options, "nodefer")) {
>>> +                       deferred_takeover = false;
>>> +                       continue;
>>> +               }
>>> +#endif
>>>         }
>>>         return 1;
>>>   }
>>> @@ -3100,6 +3112,9 @@ static int fbcon_fb_unregistered(struct fb_info
>>> *info)
>>>         WARN_CONSOLE_UNLOCKED();
>>>   +     if (deferred_takeover)
>>> +               return 0;
>>> +
>>>         idx = info->node;
>>>         for (i = first_fb_vc; i <= last_fb_vc; i++) {
>>>                 if (con2fb_map[i] == idx)
>>> @@ -3140,6 +3155,13 @@ static void fbcon_remap_all(int idx)
>>>         WARN_CONSOLE_UNLOCKED();
>>>   +     if (deferred_takeover) {
>>> +               for (i = first_fb_vc; i <= last_fb_vc; i++)
>>> +                       con2fb_map_boot[i] = idx;
>>> +               fbcon_map_override();
>>> +               return;
>>> +       }
>>> +
>>>         for (i = first_fb_vc; i <= last_fb_vc; i++)
>>>                 set_con2fb_map(i, idx, 0);
>>>   @@ -3191,6 +3213,11 @@ static int fbcon_fb_registered(struct fb_info
>>> *info)
>>>         idx = info->node;
>>>         fbcon_select_primary(info);
>>>   +     if (deferred_takeover) {
>>> +               pr_info("fbcon: Deferring console take-over\n");
>>> +               return 0;
>>> +       }
>>> +
>>>         if (info_idx == -1) {
>>>                 for (i = first_fb_vc; i <= last_fb_vc; i++) {
>>>                         if (con2fb_map_boot[i] == idx) {
>>> @@ -3566,8 +3593,46 @@ static int fbcon_init_device(void)
>>>         return 0;
>>>   }
>>>   +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
>>> +static struct notifier_block fbcon_output_nb;
>>> +
>>> +static int fbcon_output_notifier(struct notifier_block *nb,
>>> +                                unsigned long action, void *data)
>>> +{
>>> +       int i;
>>> +
>>> +       WARN_CONSOLE_UNLOCKED();
>>> +
>>> +       pr_info("fbcon: Taking over console\n");
>>> +
>>> +       dummycon_unregister_output_notifier(&fbcon_output_nb);
>>> +       deferred_takeover = false;
>>> +       logo_shown = FBCON_LOGO_DONTSHOW;
>>> +
>>> +       for (i = 0; i < FB_MAX; i++) {
>>> +               if (registered_fb[i])
>>> +                       fbcon_fb_registered(registered_fb[i]);
>>> +       }
>>> +
>>> +       return NOTIFY_OK;
>>> +}
>>> +
>>> +static void fbcon_register_output_notifier(void)
>>> +{
>>> +       fbcon_output_nb.notifier_call = fbcon_output_notifier;
>>> +       dummycon_register_output_notifier(&fbcon_output_nb);
>>> +}
>>> +#else
>>> +static inline void fbcon_register_output_notifier(void) {}
>>> +#endif
>>> +
>>>   static void fbcon_start(void)
>>>   {
>>> +       if (deferred_takeover) {
>>> +               fbcon_register_output_notifier();
>>> +               return;
>>> +       }
>>> +
>>>         if (num_registered_fb) {
>>>                 int i;
>>>   @@ -3594,6 +3659,13 @@ static void fbcon_exit(void)
>>>         if (fbcon_has_exited)
>>>                 return;
>>>   +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
>>> +       if (deferred_takeover) {
>>> +               dummycon_unregister_output_notifier(&fbcon_output_nb);
>>> +               deferred_takeover = false;
>>> +       }
>>> +#endif
>>> +
>>>         kfree((void *)softback_buf);
>>>         softback_buf = 0UL;
>>>   diff --git a/include/linux/console.h b/include/linux/console.h
>>> index dfd6b0e97855..f59f3dbca65c 100644
>>> --- a/include/linux/console.h
>>> +++ b/include/linux/console.h
>>> @@ -21,6 +21,7 @@ struct console_font_op;
>>>   struct console_font;
>>>   struct module;
>>>   struct tty_struct;
>>> +struct notifier_block;
>>>     /*
>>>    * this is what the terminal answers to a ESC-Z or csi0c query.
>>> @@ -220,4 +221,8 @@ static inline bool vgacon_text_force(void) { return
>>> false; }
>>>     extern void console_init(void);
>>>   +/* For deferred console takeover */
>>> +void dummycon_register_output_notifier(struct notifier_block *nb);
>>> +void dummycon_unregister_output_notifier(struct notifier_block *nb);
>>> +
>>>   #endif /* _LINUX_CONSOLE_H */
>>> --
>>> 2.17.1
>>>
>>> _______________________________________________
>>> dri-devel mailing list
>>> dri-devel@lists.freedesktop.org
>>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>>
>>
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel



-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

Re: [PATCH v3 3/3] console/fbcon: Add support for deferred console takeover

[Hans de Goede]

Hi,

On 28-06-18 10:37, Daniel Vetter wrote:
> On Thu, Jun 28, 2018 at 10:20 AM, Hans de Goede <hdegoede@redhat.com> wrote:
>> Hi,
>>
>> On 28-06-18 09:55, Daniel Vetter wrote:
>>>
>>> On Tue, Jun 26, 2018 at 08:36:12PM +0200, Hans de Goede wrote:
>>>>
>>>> Currently fbcon claims fbdevs as soon as they are registered and takes
>>>> over
>>>> the console as soon as the first fbdev gets registered.
>>>>
>>>> This behavior is undesirable in cases where a smooth graphical bootup is
>>>> desired, in such cases we typically want the contents of the framebuffer
>>>> (typically a vendor logo) to stay in place as is.
>>>>
>>>> The current solution for this problem (on embedded systems) is to not
>>>> enable fbcon.
>>>>
>>>> This commit adds a new FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER config
>>>> option,
>>>> which when enabled defers fbcon taking over the console from the dummy
>>>> console until the first text is displayed on the console. Together with
>>>> the
>>>> "quiet" kernel commandline option, this allows fbcon to still be used
>>>> together with a smooth graphical bootup, having it take over the console
>>>> as
>>>> soon as e.g. an error message is logged.
>>>>
>>>> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
>>>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>>>
>>>
>>> A bit a late comment, and feel free to reject: Have you considered
>>> registering the fbcon driver, but not doing any modesets until the very
>>> first real message shows up?
>>
>>
>> I have tried something like that, but it did not work out, this patch-set
>> actually is my 3th attempt at this (the other 2 were never posted
>> because they did not work).
>>
>> The fbcon code is woven quite tightly into the console code, so this was
>> the only clean way I could find to achieve what I want.
> 
> I assumed/feared as much. Would be good to cover that in the commit
> message, to justify your approach better.

Ok, v5 with an updated commit message (and without any code changes)
coming up.

Regards,

Hans



>>>> ---
>>>> Changes in v2:
>>>> -Check the whole string when checking for erases in putcs, instead of
>>>> just
>>>>    the first char
>>>> -Make dummycon_blank return 1, so that a redraw gets triggered and any
>>>> text
>>>>    rendered while blanked gets output so that it can trigger a deferred
>>>>    takeover if one is pending
>>>>
>>>> Changes in v3:
>>>> -Call WARN_CONSOLE_UNLOCKED() from fbcon_output_notifier()
>>>> -Unregister the notifier on fbcon_exit()
>>>> -Document the fbcon=nodefer commandline option in
>>>> Documentation/fb/fbcon.txt
>>>> ---
>>>>    Documentation/fb/fbcon.txt       |  7 ++++
>>>>    drivers/video/console/Kconfig    | 11 +++++
>>>>    drivers/video/console/dummycon.c | 67 +++++++++++++++++++++++++----
>>>>    drivers/video/fbdev/core/fbcon.c | 72 ++++++++++++++++++++++++++++++++
>>>>    include/linux/console.h          |  5 +++
>>>>    5 files changed, 154 insertions(+), 8 deletions(-)
>>>>
>>>> diff --git a/Documentation/fb/fbcon.txt b/Documentation/fb/fbcon.txt
>>>> index 79c22d096bbc..d4d642e1ce9c 100644
>>>> --- a/Documentation/fb/fbcon.txt
>>>> +++ b/Documentation/fb/fbcon.txt
>>>> @@ -155,6 +155,13 @@ C. Boot options
>>>>          used by text. By default, this area will be black. The 'color'
>>>> value
>>>>          is an integer number that depends on the framebuffer driver being
>>>> used.
>>>>    +6. fbcon=nodefer
>>>> +
>>>> +       If the kernel is compiled with deferred fbcon takeover support,
>>>> normally
>>>> +       the framebuffer contents, left in place by the
>>>> firmware/bootloader, will
>>>> +       be preserved until there actually is some text is output to the
>>>> console.
>>>> +       This option causes fbcon to bind immediately to the fbdev device.
>>>> +
>>>>    C. Attaching, Detaching and Unloading
>>>>      Before going on how to attach, detach and unload the framebuffer
>>>> console, an
>>>> diff --git a/drivers/video/console/Kconfig
>>>> b/drivers/video/console/Kconfig
>>>> index 4110ba7d7ca9..e91edef98633 100644
>>>> --- a/drivers/video/console/Kconfig
>>>> +++ b/drivers/video/console/Kconfig
>>>> @@ -150,6 +150,17 @@ config FRAMEBUFFER_CONSOLE_ROTATION
>>>>             such that other users of the framebuffer will remain normally
>>>>             oriented.
>>>>    +config FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
>>>> +       bool "Framebuffer Console Deferred Takeover"
>>>> +       depends on FRAMEBUFFER_CONSOLE=y && DUMMY_CONSOLE=y
>>>> +       help
>>>> +         If enabled this defers the framebuffer console taking over the
>>>> +         console from the dummy console until the first text is
>>>> displayed on
>>>> +         the console. This is useful in combination with the "quiet"
>>>> kernel
>>>> +         commandline option to keep the framebuffer contents initially
>>>> put up
>>>> +         by the firmware in place, rather then replacing the contents
>>>> with a
>>>> +         black screen as soon as fbcon loads.
>>>> +
>>>>    config STI_CONSOLE
>>>>            bool "STI text console"
>>>>          depends on PARISC && HAS_IOMEM
>>>> diff --git a/drivers/video/console/dummycon.c
>>>> b/drivers/video/console/dummycon.c
>>>> index f2eafe2ed980..45ad925ad5f8 100644
>>>> --- a/drivers/video/console/dummycon.c
>>>> +++ b/drivers/video/console/dummycon.c
>>>> @@ -26,6 +26,65 @@
>>>>    #define DUMMY_ROWS    CONFIG_DUMMY_CONSOLE_ROWS
>>>>    #endif
>>>>    +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
>>>> +/* These are both protected by the console_lock */
>>>> +static RAW_NOTIFIER_HEAD(dummycon_output_nh);
>>>> +static bool dummycon_putc_called;
>>>> +
>>>> +void dummycon_register_output_notifier(struct notifier_block *nb)
>>>> +{
>>>> +       raw_notifier_chain_register(&dummycon_output_nh, nb);
>>>> +
>>>> +       if (dummycon_putc_called)
>>>> +               nb->notifier_call(nb, 0, NULL);
>>>> +}
>>>> +
>>>> +void dummycon_unregister_output_notifier(struct notifier_block *nb)
>>>> +{
>>>> +       raw_notifier_chain_unregister(&dummycon_output_nh, nb);
>>>> +}
>>>> +
>>>> +static void dummycon_putc(struct vc_data *vc, int c, int ypos, int xpos)
>>>> +{
>>>> +       dummycon_putc_called = true;
>>>> +       raw_notifier_call_chain(&dummycon_output_nh, 0, NULL);
>>>> +}
>>>> +
>>>> +static void dummycon_putcs(struct vc_data *vc, const unsigned short *s,
>>>> +                          int count, int ypos, int xpos)
>>>> +{
>>>> +       int i;
>>>> +
>>>> +       if (!dummycon_putc_called) {
>>>> +               /* Ignore erases */
>>>> +               for (i = 0 ; i < count; i++) {
>>>> +                       if (s[i] != vc->vc_video_erase_char)
>>>> +                               break;
>>>> +               }
>>>> +               if (i == count)
>>>> +                       return;
>>>> +
>>>> +               dummycon_putc_called = true;
>>>> +       }
>>>> +
>>>> +       raw_notifier_call_chain(&dummycon_output_nh, 0, NULL);
>>>> +}
>>>> +
>>>> +static int dummycon_blank(struct vc_data *vc, int blank, int
>>>> mode_switch)
>>>> +{
>>>> +       /* Redraw, so that we get putc(s) for output done while blanked
>>>> */
>>>> +       return 1;
>>>> +}
>>>> +#else
>>>> +static void dummycon_putc(struct vc_data *vc, int c, int ypos, int xpos)
>>>> { }
>>>> +static void dummycon_putcs(struct vc_data *vc, const unsigned short *s,
>>>> +                          int count, int ypos, int xpos) { }
>>>> +static int dummycon_blank(struct vc_data *vc, int blank, int
>>>> mode_switch)
>>>> +{
>>>> +       return 0;
>>>> +}
>>>> +#endif
>>>> +
>>>>    static const char *dummycon_startup(void)
>>>>    {
>>>>        return "dummy device";
>>>> @@ -44,9 +103,6 @@ static void dummycon_init(struct vc_data *vc, int
>>>> init)
>>>>    static void dummycon_deinit(struct vc_data *vc) { }
>>>>    static void dummycon_clear(struct vc_data *vc, int sy, int sx, int
>>>> height,
>>>>                             int width) { }
>>>> -static void dummycon_putc(struct vc_data *vc, int c, int ypos, int xpos)
>>>> { }
>>>> -static void dummycon_putcs(struct vc_data *vc, const unsigned short *s,
>>>> -                          int count, int ypos, int xpos) { }
>>>>    static void dummycon_cursor(struct vc_data *vc, int mode) { }
>>>>      static bool dummycon_scroll(struct vc_data *vc, unsigned int top,
>>>> @@ -61,11 +117,6 @@ static int dummycon_switch(struct vc_data *vc)
>>>>          return 0;
>>>>    }
>>>>    -static int dummycon_blank(struct vc_data *vc, int blank, int
>>>> mode_switch)
>>>> -{
>>>> -       return 0;
>>>> -}
>>>> -
>>>>    static int dummycon_font_set(struct vc_data *vc, struct console_font
>>>> *font,
>>>>                               unsigned int flags)
>>>>    {
>>>> diff --git a/drivers/video/fbdev/core/fbcon.c
>>>> b/drivers/video/fbdev/core/fbcon.c
>>>> index cd8d52a967aa..5fb156bdcf4e 100644
>>>> --- a/drivers/video/fbdev/core/fbcon.c
>>>> +++ b/drivers/video/fbdev/core/fbcon.c
>>>> @@ -129,6 +129,12 @@ static inline void fbcon_map_override(void)
>>>>    }
>>>>    #endif /* CONFIG_FRAMEBUFFER_CONSOLE_DETECT_PRIMARY */
>>>>    +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
>>>> +static bool deferred_takeover = true;
>>>> +#else
>>>> +#define deferred_takeover false
>>>> +#endif
>>>> +
>>>>    /* font data */
>>>>    static char fontname[40];
>>>>    @@ -499,6 +505,12 @@ static int __init fb_console_setup(char *this_opt)
>>>>                                  margin_color = simple_strtoul(options,
>>>> &options, 0);
>>>>                          continue;
>>>>                  }
>>>> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
>>>> +               if (!strcmp(options, "nodefer")) {
>>>> +                       deferred_takeover = false;
>>>> +                       continue;
>>>> +               }
>>>> +#endif
>>>>          }
>>>>          return 1;
>>>>    }
>>>> @@ -3100,6 +3112,9 @@ static int fbcon_fb_unregistered(struct fb_info
>>>> *info)
>>>>          WARN_CONSOLE_UNLOCKED();
>>>>    +     if (deferred_takeover)
>>>> +               return 0;
>>>> +
>>>>          idx = info->node;
>>>>          for (i = first_fb_vc; i <= last_fb_vc; i++) {
>>>>                  if (con2fb_map[i] == idx)
>>>> @@ -3140,6 +3155,13 @@ static void fbcon_remap_all(int idx)
>>>>          WARN_CONSOLE_UNLOCKED();
>>>>    +     if (deferred_takeover) {
>>>> +               for (i = first_fb_vc; i <= last_fb_vc; i++)
>>>> +                       con2fb_map_boot[i] = idx;
>>>> +               fbcon_map_override();
>>>> +               return;
>>>> +       }
>>>> +
>>>>          for (i = first_fb_vc; i <= last_fb_vc; i++)
>>>>                  set_con2fb_map(i, idx, 0);
>>>>    @@ -3191,6 +3213,11 @@ static int fbcon_fb_registered(struct fb_info
>>>> *info)
>>>>          idx = info->node;
>>>>          fbcon_select_primary(info);
>>>>    +     if (deferred_takeover) {
>>>> +               pr_info("fbcon: Deferring console take-over\n");
>>>> +               return 0;
>>>> +       }
>>>> +
>>>>          if (info_idx == -1) {
>>>>                  for (i = first_fb_vc; i <= last_fb_vc; i++) {
>>>>                          if (con2fb_map_boot[i] == idx) {
>>>> @@ -3566,8 +3593,46 @@ static int fbcon_init_device(void)
>>>>          return 0;
>>>>    }
>>>>    +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
>>>> +static struct notifier_block fbcon_output_nb;
>>>> +
>>>> +static int fbcon_output_notifier(struct notifier_block *nb,
>>>> +                                unsigned long action, void *data)
>>>> +{
>>>> +       int i;
>>>> +
>>>> +       WARN_CONSOLE_UNLOCKED();
>>>> +
>>>> +       pr_info("fbcon: Taking over console\n");
>>>> +
>>>> +       dummycon_unregister_output_notifier(&fbcon_output_nb);
>>>> +       deferred_takeover = false;
>>>> +       logo_shown = FBCON_LOGO_DONTSHOW;
>>>> +
>>>> +       for (i = 0; i < FB_MAX; i++) {
>>>> +               if (registered_fb[i])
>>>> +                       fbcon_fb_registered(registered_fb[i]);
>>>> +       }
>>>> +
>>>> +       return NOTIFY_OK;
>>>> +}
>>>> +
>>>> +static void fbcon_register_output_notifier(void)
>>>> +{
>>>> +       fbcon_output_nb.notifier_call = fbcon_output_notifier;
>>>> +       dummycon_register_output_notifier(&fbcon_output_nb);
>>>> +}
>>>> +#else
>>>> +static inline void fbcon_register_output_notifier(void) {}
>>>> +#endif
>>>> +
>>>>    static void fbcon_start(void)
>>>>    {
>>>> +       if (deferred_takeover) {
>>>> +               fbcon_register_output_notifier();
>>>> +               return;
>>>> +       }
>>>> +
>>>>          if (num_registered_fb) {
>>>>                  int i;
>>>>    @@ -3594,6 +3659,13 @@ static void fbcon_exit(void)
>>>>          if (fbcon_has_exited)
>>>>                  return;
>>>>    +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
>>>> +       if (deferred_takeover) {
>>>> +               dummycon_unregister_output_notifier(&fbcon_output_nb);
>>>> +               deferred_takeover = false;
>>>> +       }
>>>> +#endif
>>>> +
>>>>          kfree((void *)softback_buf);
>>>>          softback_buf = 0UL;
>>>>    diff --git a/include/linux/console.h b/include/linux/console.h
>>>> index dfd6b0e97855..f59f3dbca65c 100644
>>>> --- a/include/linux/console.h
>>>> +++ b/include/linux/console.h
>>>> @@ -21,6 +21,7 @@ struct console_font_op;
>>>>    struct console_font;
>>>>    struct module;
>>>>    struct tty_struct;
>>>> +struct notifier_block;
>>>>      /*
>>>>     * this is what the terminal answers to a ESC-Z or csi0c query.
>>>> @@ -220,4 +221,8 @@ static inline bool vgacon_text_force(void) { return
>>>> false; }
>>>>      extern void console_init(void);
>>>>    +/* For deferred console takeover */
>>>> +void dummycon_register_output_notifier(struct notifier_block *nb);
>>>> +void dummycon_unregister_output_notifier(struct notifier_block *nb);
>>>> +
>>>>    #endif /* _LINUX_CONSOLE_H */
>>>> --
>>>> 2.17.1
>>>>
>>>> _______________________________________________
>>>> dri-devel mailing list
>>>> dri-devel@lists.freedesktop.org
>>>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>>>
>>>
>> _______________________________________________
>> dri-devel mailing list
>> dri-devel@lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
> 
> 
> 

Re: [PATCH v3 3/3] console/fbcon: Add support for deferred console takeover

[Andy Shevchenko]

On Tue, Jun 26, 2018 at 9:29 PM, Hans de Goede <hdegoede@redhat.com> wrote:

>>> +       for (i = 0; i < FB_MAX; i++) {
>>> +               if (registered_fb[i])
>>> +                       fbcon_fb_registered(registered_fb[i]);
>>> +       }

>> Simple git grep shows that we perhaps do
>>
>> #define for_each_registered_fbcon(i) ...
>>
>> (As an example see for_each_pci_bridge() how it's done there)
>
>
> This is probably a worthwhile cleanup for all the fbdev related
> code / drivers. But outside of the scope of this patchset.

True.

Yisheng, in case you are interested in doing such clean up...

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v3 3/3] console/fbcon: Add support for deferred console takeover

[Hans de Goede]

Hi,

On 26-06-18 19:12, Andy Shevchenko wrote:
> On Tue, Jun 26, 2018 at 4:55 PM, Hans de Goede <hdegoede@redhat.com> wrote:
>> Currently fbcon claims fbdevs as soon as they are registered and takes over
>> the console as soon as the first fbdev gets registered.
>>
>> This behavior is undesirable in cases where a smooth graphical bootup is
>> desired, in such cases we typically want the contents of the framebuffer
>> (typically a vendor logo) to stay in place as is.
>>
>> The current solution for this problem (on embedded systems) is to not
>> enable fbcon.
>>
>> This commit adds a new FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER config option,
>> which when enabled defers fbcon taking over the console from the dummy
>> console until the first text is displayed on the console. Together with the
>> "quiet" kernel commandline option, this allows fbcon to still be used
>> together with a smooth graphical bootup, having it take over the console as
>> soon as e.g. an error message is logged.
> 
>> +       for (i = 0; i < FB_MAX; i++) {
>> +               if (registered_fb[i])
>> +                       fbcon_fb_registered(registered_fb[i]);
>> +       }
> 
> Simple git grep shows that we perhaps do
> 
> #define for_each_registered_fbcon(i) ...
> 
> (As an example see for_each_pci_bridge() how it's done there)

This is probably a worthwhile cleanup for all the fbdev related
code / drivers. But outside of the scope of this patchset.

Regards,

Hans

Re: [PATCH v3 3/3] console/fbcon: Add support for deferred console takeover

[Andy Shevchenko]

On Tue, Jun 26, 2018 at 8:12 PM, Andy Shevchenko
<andy.shevchenko@gmail.com> wrote:
> On Tue, Jun 26, 2018 at 4:55 PM, Hans de Goede <hdegoede@redhat.com> wrote:

>> +       for (i = 0; i < FB_MAX; i++) {
>> +               if (registered_fb[i])
>> +                       fbcon_fb_registered(registered_fb[i]);
>> +       }
>
> Simple git grep shows that we perhaps do
>
> #define for_each_registered_fbcon(i) ...

(Or just ..._fb() since it looks like iteration over framebuffers, not
exactly consoles)

>
> (As an example see for_each_pci_bridge() how it's done there)



-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v3 3/3] console/fbcon: Add support for deferred console takeover

[Andy Shevchenko]

On Tue, Jun 26, 2018 at 4:55 PM, Hans de Goede <hdegoede@redhat.com> wrote:
> Currently fbcon claims fbdevs as soon as they are registered and takes over
> the console as soon as the first fbdev gets registered.
>
> This behavior is undesirable in cases where a smooth graphical bootup is
> desired, in such cases we typically want the contents of the framebuffer
> (typically a vendor logo) to stay in place as is.
>
> The current solution for this problem (on embedded systems) is to not
> enable fbcon.
>
> This commit adds a new FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER config option,
> which when enabled defers fbcon taking over the console from the dummy
> console until the first text is displayed on the console. Together with the
> "quiet" kernel commandline option, this allows fbcon to still be used
> together with a smooth graphical bootup, having it take over the console as
> soon as e.g. an error message is logged.

> +       for (i = 0; i < FB_MAX; i++) {
> +               if (registered_fb[i])
> +                       fbcon_fb_registered(registered_fb[i]);
> +       }

Simple git grep shows that we perhaps do

#define for_each_registered_fbcon(i) ...

(As an example see for_each_pci_bridge() how it's done there)

-- 
With Best Regards,
Andy Shevchenko

[PATCH v3 3/3] console/fbcon: Add support for deferred console takeover

[Hans de Goede]

Currently fbcon claims fbdevs as soon as they are registered and takes over
the console as soon as the first fbdev gets registered.

This behavior is undesirable in cases where a smooth graphical bootup is
desired, in such cases we typically want the contents of the framebuffer
(typically a vendor logo) to stay in place as is.

The current solution for this problem (on embedded systems) is to not
enable fbcon.

This commit adds a new FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER config option,
which when enabled defers fbcon taking over the console from the dummy
console until the first text is displayed on the console. Together with the
"quiet" kernel commandline option, this allows fbcon to still be used
together with a smooth graphical bootup, having it take over the console as
soon as e.g. an error message is logged.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
Changes in v2:
-Check the whole string when checking for erases in putcs, instead of just
 the first char
-Make dummycon_blank return 1, so that a redraw gets triggered and any text
 rendered while blanked gets output so that it can trigger a deferred
 takeover if one is pending

Changes in v3:
-Call WARN_CONSOLE_UNLOCKED() from fbcon_output_notifier()
-Unregister the notifier on fbcon_exit()
-Document the fbcon=nodefer commandline option in Documentation/fb/fbcon.txt
---
 Documentation/fb/fbcon.txt       |  7 ++++
 drivers/video/console/Kconfig    | 11 +++++
 drivers/video/console/dummycon.c | 67 +++++++++++++++++++++++++----
 drivers/video/fbdev/core/fbcon.c | 72 ++++++++++++++++++++++++++++++++
 include/linux/console.h          |  5 +++
 5 files changed, 154 insertions(+), 8 deletions(-)

diff --git a/Documentation/fb/fbcon.txt b/Documentation/fb/fbcon.txt
index 79c22d096bbc..d4d642e1ce9c 100644
--- a/Documentation/fb/fbcon.txt
+++ b/Documentation/fb/fbcon.txt
@@ -155,6 +155,13 @@ C. Boot options
 	used by text. By default, this area will be black. The 'color' value
 	is an integer number that depends on the framebuffer driver being used.
 
+6. fbcon=nodefer
+
+	If the kernel is compiled with deferred fbcon takeover support, normally
+	the framebuffer contents, left in place by the firmware/bootloader, will
+	be preserved until there actually is some text is output to the console.
+	This option causes fbcon to bind immediately to the fbdev device.
+
 C. Attaching, Detaching and Unloading
 
 Before going on how to attach, detach and unload the framebuffer console, an
diff --git a/drivers/video/console/Kconfig b/drivers/video/console/Kconfig
index 4110ba7d7ca9..e91edef98633 100644
--- a/drivers/video/console/Kconfig
+++ b/drivers/video/console/Kconfig
@@ -150,6 +150,17 @@ config FRAMEBUFFER_CONSOLE_ROTATION
          such that other users of the framebuffer will remain normally
          oriented.
 
+config FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
+	bool "Framebuffer Console Deferred Takeover"
+	depends on FRAMEBUFFER_CONSOLE=y && DUMMY_CONSOLE=y
+	help
+	  If enabled this defers the framebuffer console taking over the
+	  console from the dummy console until the first text is displayed on
+	  the console. This is useful in combination with the "quiet" kernel
+	  commandline option to keep the framebuffer contents initially put up
+	  by the firmware in place, rather then replacing the contents with a
+	  black screen as soon as fbcon loads.
+
 config STI_CONSOLE
         bool "STI text console"
 	depends on PARISC && HAS_IOMEM
diff --git a/drivers/video/console/dummycon.c b/drivers/video/console/dummycon.c
index f2eafe2ed980..45ad925ad5f8 100644
--- a/drivers/video/console/dummycon.c
+++ b/drivers/video/console/dummycon.c
@@ -26,6 +26,65 @@
 #define DUMMY_ROWS	CONFIG_DUMMY_CONSOLE_ROWS
 #endif
 
+#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
+/* These are both protected by the console_lock */
+static RAW_NOTIFIER_HEAD(dummycon_output_nh);
+static bool dummycon_putc_called;
+
+void dummycon_register_output_notifier(struct notifier_block *nb)
+{
+	raw_notifier_chain_register(&dummycon_output_nh, nb);
+
+	if (dummycon_putc_called)
+		nb->notifier_call(nb, 0, NULL);
+}
+
+void dummycon_unregister_output_notifier(struct notifier_block *nb)
+{
+	raw_notifier_chain_unregister(&dummycon_output_nh, nb);
+}
+
+static void dummycon_putc(struct vc_data *vc, int c, int ypos, int xpos)
+{
+	dummycon_putc_called = true;
+	raw_notifier_call_chain(&dummycon_output_nh, 0, NULL);
+}
+
+static void dummycon_putcs(struct vc_data *vc, const unsigned short *s,
+			   int count, int ypos, int xpos)
+{
+	int i;
+
+	if (!dummycon_putc_called) {
+		/* Ignore erases */
+		for (i = 0 ; i < count; i++) {
+			if (s[i] != vc->vc_video_erase_char)
+				break;
+		}
+		if (i == count)
+			return;
+
+		dummycon_putc_called = true;
+	}
+
+	raw_notifier_call_chain(&dummycon_output_nh, 0, NULL);
+}
+
+static int dummycon_blank(struct vc_data *vc, int blank, int mode_switch)
+{
+	/* Redraw, so that we get putc(s) for output done while blanked */
+	return 1;
+}
+#else
+static void dummycon_putc(struct vc_data *vc, int c, int ypos, int xpos) { }
+static void dummycon_putcs(struct vc_data *vc, const unsigned short *s,
+			   int count, int ypos, int xpos) { }
+static int dummycon_blank(struct vc_data *vc, int blank, int mode_switch)
+{
+	return 0;
+}
+#endif
+
 static const char *dummycon_startup(void)
 {
     return "dummy device";
@@ -44,9 +103,6 @@ static void dummycon_init(struct vc_data *vc, int init)
 static void dummycon_deinit(struct vc_data *vc) { }
 static void dummycon_clear(struct vc_data *vc, int sy, int sx, int height,
 			   int width) { }
-static void dummycon_putc(struct vc_data *vc, int c, int ypos, int xpos) { }
-static void dummycon_putcs(struct vc_data *vc, const unsigned short *s,
-			   int count, int ypos, int xpos) { }
 static void dummycon_cursor(struct vc_data *vc, int mode) { }
 
 static bool dummycon_scroll(struct vc_data *vc, unsigned int top,
@@ -61,11 +117,6 @@ static int dummycon_switch(struct vc_data *vc)
 	return 0;
 }
 
-static int dummycon_blank(struct vc_data *vc, int blank, int mode_switch)
-{
-	return 0;
-}
-
 static int dummycon_font_set(struct vc_data *vc, struct console_font *font,
 			     unsigned int flags)
 {
diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
index ac2cbdf710ee..bd5da263eaff 100644
--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -129,6 +129,12 @@ static inline void fbcon_map_override(void)
 }
 #endif /* CONFIG_FRAMEBUFFER_CONSOLE_DETECT_PRIMARY */
 
+#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
+static bool deferred_takeover = true;
+#else
+#define deferred_takeover false
+#endif
+
 /* font data */
 static char fontname[40];
 
@@ -499,6 +505,12 @@ static int __init fb_console_setup(char *this_opt)
 				margin_color = simple_strtoul(options, &options, 0);
 			continue;
 		}
+#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
+		if (!strcmp(options, "nodefer")) {
+			deferred_takeover = false;
+			continue;
+		}
+#endif
 	}
 	return 1;
 }
@@ -3096,6 +3108,9 @@ static int fbcon_fb_unregistered(struct fb_info *info)
 
 	WARN_CONSOLE_UNLOCKED();
 
+	if (deferred_takeover)
+		return 0;
+
 	idx = info->node;
 	for (i = first_fb_vc; i <= last_fb_vc; i++) {
 		if (con2fb_map[i] == idx)
@@ -3135,6 +3150,13 @@ static void fbcon_remap_all(int idx)
 
 	WARN_CONSOLE_UNLOCKED();
 
+	if (deferred_takeover) {
+		for (i = first_fb_vc; i <= last_fb_vc; i++)
+			con2fb_map_boot[i] = idx;
+		fbcon_map_override();
+		return;
+	}
+
 	for (i = first_fb_vc; i <= last_fb_vc; i++)
 		set_con2fb_map(i, idx, 0);
 
@@ -3185,6 +3207,11 @@ static int fbcon_fb_registered(struct fb_info *info)
 	idx = info->node;
 	fbcon_select_primary(info);
 
+	if (deferred_takeover) {
+		pr_info("fbcon: Deferring console take-over\n");
+		return 0;
+	}
+
 	if (info_idx == -1) {
 		for (i = first_fb_vc; i <= last_fb_vc; i++) {
 			if (con2fb_map_boot[i] == idx) {
@@ -3559,8 +3586,46 @@ static int fbcon_init_device(void)
 	return 0;
 }
 
+#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
+static struct notifier_block fbcon_output_nb;
+
+static int fbcon_output_notifier(struct notifier_block *nb,
+				 unsigned long action, void *data)
+{
+	int i;
+
+	WARN_CONSOLE_UNLOCKED();
+
+	pr_info("fbcon: Taking over console\n");
+
+	dummycon_unregister_output_notifier(&fbcon_output_nb);
+	deferred_takeover = false;
+	logo_shown = FBCON_LOGO_DONTSHOW;
+
+	for (i = 0; i < FB_MAX; i++) {
+		if (registered_fb[i])
+			fbcon_fb_registered(registered_fb[i]);
+	}
+
+	return NOTIFY_OK;
+}
+
+static void fbcon_register_output_notifier(void)
+{
+	fbcon_output_nb.notifier_call = fbcon_output_notifier;
+	dummycon_register_output_notifier(&fbcon_output_nb);
+}
+#else
+static inline void fbcon_register_output_notifier(void) {}
+#endif
+
 static void fbcon_start(void)
 {
+	if (deferred_takeover) {
+		fbcon_register_output_notifier();
+		return;
+	}
+
 	if (num_registered_fb) {
 		int i;
 
@@ -3587,6 +3652,13 @@ static void fbcon_exit(void)
 	if (fbcon_has_exited)
 		return;
 
+#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
+	if (deferred_takeover) {
+		dummycon_unregister_output_notifier(&fbcon_output_nb);
+		deferred_takeover = false;
+	}
+#endif
+
 	kfree((void *)softback_buf);
 	softback_buf = 0UL;
 
diff --git a/include/linux/console.h b/include/linux/console.h
index dfd6b0e97855..f59f3dbca65c 100644
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -21,6 +21,7 @@ struct console_font_op;
 struct console_font;
 struct module;
 struct tty_struct;
+struct notifier_block;
 
 /*
  * this is what the terminal answers to a ESC-Z or csi0c query.
@@ -220,4 +221,8 @@ static inline bool vgacon_text_force(void) { return false; }
 
 extern void console_init(void);
 
+/* For deferred console takeover */
+void dummycon_register_output_notifier(struct notifier_block *nb);
+void dummycon_unregister_output_notifier(struct notifier_block *nb);
+
 #endif /* _LINUX_CONSOLE_H */
-- 
2.17.1