From b6b5bcae7aa5248d2c102991c93aea1cae5d4932 Mon Sep 17 00:00:00 2001 From: Thomas Zimmermann Date: Tue, 20 May 2025 09:14:00 +0200 Subject: [PATCH] dummycon: Trigger redraw when switching consoles with deferred takeover [ Upstream commit 03bcbbb3995ba5df43af9aba45334e35f2dfe27b ] Signal vt subsystem to redraw console when switching to dummycon with deferred takeover enabled. Makes the console switch to fbcon and displays the available output. With deferred takeover enabled, dummycon acts as the placeholder until the first output to the console happens. At that point, fbcon takes over. If the output happens while dummycon is not active, it cannot inform fbcon. This is the case if the vt subsystem runs in graphics mode. A typical graphical boot starts plymouth, a display manager and a compositor; all while leaving out dummycon. Switching to a text-mode console leaves the console with dummycon even if a getty terminal has been started. Returning true from dummycon's con_switch helper signals the vt subsystem to redraw the screen. If there's output available dummycon's con_putc{s} helpers trigger deferred takeover of fbcon, which sets a display mode and displays the output. If no output is available, dummycon remains active. v2: - make the comment slightly more verbose (Javier) Signed-off-by: Thomas Zimmermann Reported-by: Andrei Borzenkov Closes: https://bugzilla.suse.com/show_bug.cgi?id=1242191 Tested-by: Andrei Borzenkov Acked-by: Javier Martinez Canillas Fixes: 83d83bebf401 ("console/fbcon: Add support for deferred console takeover") Cc: Hans de Goede Cc: linux-fbdev@vger.kernel.org Cc: dri-devel@lists.freedesktop.org Cc: # v4.19+ Link: https://lore.kernel.org/r/20250520071418.8462-1-tzimmermann@suse.de Signed-off-by: Sasha Levin --- drivers/video/console/dummycon.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-) diff --git a/drivers/video/console/dummycon.c b/drivers/video/console/dummycon.c index d701f2b51f5b..d99e1b3e4e5c 100644 --- a/drivers/video/console/dummycon.c +++ b/drivers/video/console/dummycon.c @@ -82,6 +82,15 @@ 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; } + +static bool dummycon_switch(struct vc_data *vc) +{ + /* + * Redraw, so that we get putc(s) for output done while switched + * away. Informs deferred consoles to take over the display. + */ + return true; +} #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, @@ -90,6 +99,10 @@ static int dummycon_blank(struct vc_data *vc, int blank, int mode_switch) { return 0; } +static bool dummycon_switch(struct vc_data *vc) +{ + return false; +} #endif static const char *dummycon_startup(void) @@ -119,11 +132,6 @@ static bool dummycon_scroll(struct vc_data *vc, unsigned int top, return false; } -static bool dummycon_switch(struct vc_data *vc) -{ - return false; -} - /* * The console `switch' structure for the dummy console *