From 83d83bebf40132e2d55ec58af666713cc76f9764 Mon Sep 17 00:00:00 2001 From: Hans de Goede Date: Thu, 28 Jun 2018 15:20:30 +0200 Subject: console/fbcon: Add support for deferred console takeover 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. Note the choice to detect the first console output in the dummycon driver, rather then handling this entirely inside the fbcon code, was made after 2 failed attempts to handle this entirely inside the fbcon code. The fbcon code is woven quite tightly into the console code, making this to only feasible option. Reviewed-by: Daniel Vetter Signed-off-by: Hans de Goede Signed-off-by: Bartlomiej Zolnierkiewicz --- include/linux/console.h | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'include/linux/console.h') 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 */ -- cgit v1.2.3 From 56e6c104e4f151e19eb410004405ec52b4f8605a Mon Sep 17 00:00:00 2001 From: Thomas Zimmermann Date: Tue, 31 Jul 2018 13:06:57 +0200 Subject: console: Replace #if 0 with atomic var 'ignore_console_lock_warning' The macro WARN_CONSOLE_UNLOCKED prints a warning when a thread enters the console's critical section without having acquired the console lock. The console lock can be ignored when debugging the console using printk, but this makes WARN_CONSOLE_UNLOCKED generate unnecessary warnings. The variable ignore_console_lock_warning temporarily disables WARN_CONSOLE_UNLOCKED. Developers interested in debugging the console's critical sections should increment it before entering the CS and decrement it after leaving the CS. Setting ignore_console_lock_warning is only for debugging. Regular operation should not manipulate it. Acknoledgements: This patch is based on an earlier version by Steven Rostedt. The use of atomic increment/decrement was suggested by Petr Mladek. Link: http://lkml.kernel.org/r/717e6337-e7a6-7a92-1c1b-8929a25696b5@suse.de Signed-off-by: Thomas Zimmermann Acked-by: Hans de Goede Acked-by: Petr Mladek Reviewed-by: Sergey Senozhatsky Cc: Steven Rostedt (VMware) Cc: Andrew Morton [b.zolnierkie: use ] Signed-off-by: Bartlomiej Zolnierkiewicz --- include/linux/console.h | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) (limited to 'include/linux/console.h') diff --git a/include/linux/console.h b/include/linux/console.h index f59f3dbca65c..ec9bdb3d7bab 100644 --- a/include/linux/console.h +++ b/include/linux/console.h @@ -14,6 +14,7 @@ #ifndef _LINUX_CONSOLE_H_ #define _LINUX_CONSOLE_H_ 1 +#include #include struct vc_data; @@ -201,11 +202,14 @@ void vcs_make_sysfs(int index); void vcs_remove_sysfs(int index); /* Some debug stub to catch some of the obvious races in the VT code */ -#if 1 -#define WARN_CONSOLE_UNLOCKED() WARN_ON(!is_console_locked() && !oops_in_progress) -#else -#define WARN_CONSOLE_UNLOCKED() -#endif +#define WARN_CONSOLE_UNLOCKED() \ + WARN_ON(!atomic_read(&ignore_console_lock_warning) && \ + !is_console_locked() && !oops_in_progress) +/* + * Increment ignore_console_lock_warning if you need to quiet + * WARN_CONSOLE_UNLOCKED() for debugging purposes. + */ +extern atomic_t ignore_console_lock_warning; /* VESA Blanking Levels */ #define VESA_NO_BLANKING 0 -- cgit v1.2.3