| Message ID | 20240206101100.25536-2-daniel.van.vugt@canonical.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v2,1/2] dummycon: Add dummycon_(un)register_switch_notifier | expand |
On Tue, Feb 06, 2024 at 06:10:51PM +0800, Daniel van Vugt wrote: > Until now, deferred console takeover only meant defer until there is > output. But that risks stepping on the toes of userspace splash screens, > as console messages may appear before the splash screen. So check the > command line for the expectation of userspace splash and if present then > extend the deferral until after the first switch. > > V2: Added Kconfig option instead of hard coding "splash". > > Closes: https://bugs.launchpad.net/bugs/1970069 > Cc: Mario Limonciello <mario.limonciello@amd.com> > Signed-off-by: Daniel van Vugt <daniel.van.vugt@canonical.com> > --- > drivers/video/console/Kconfig | 13 +++++++++++ > drivers/video/fbdev/core/fbcon.c | 38 ++++++++++++++++++++++++++++++-- > 2 files changed, 49 insertions(+), 2 deletions(-) > > diff --git a/drivers/video/console/Kconfig b/drivers/video/console/Kconfig > index bc31db6ef7..a6e371bfb4 100644 > --- a/drivers/video/console/Kconfig > +++ b/drivers/video/console/Kconfig > @@ -138,6 +138,19 @@ config FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER > by the firmware in place, rather then replacing the contents with a > black screen as soon as fbcon loads. > > +config FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION > + string "Framebuffer Console Deferred Takeover Condition" > + depends on FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER > + default "splash" > + help > + If enabled this defers further the framebuffer console taking over > + until the first console switch has occurred. And even then only if > + text has been output, and only if the specified parameter is found > + on the command line. This ensures fbcon does not interrupt userspace > + splash screens such as Plymouth which may be yet to start rendering > + at the time of the first console output. "splash" is the simplest > + distro-agnostic condition for this that Plymouth checks for. Hm this seems a bit strange since a lot of complexity that no one needs, also my impression is that it's rather distro specific how you want this to work. So why not just a Kconfig option that lets you choose how much you want to delay fbcon setup, with the following options: - no delay at all - dely until first output from the console (which then works for distros which set a log-level to suppress unwanted stuff) - delay until first vt-switch. In that case I don't think we also need to delay for first output, since vt switch usually means you'll get first output right away (if it's a vt terminal) or you switch to a different graphical console (which will keep fbcon fully suppressed on the drm side). I think you could even reuse the existing CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER for this, and then just compile-time select which kind of notifier to register (well plus the check for "splash" on the cmdline for the vt switch one I guess). Thoughts? Cheers, Sima > + > config STI_CONSOLE > bool "STI text console" > depends on PARISC && HAS_IOMEM > diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c > index 63af6ab034..98155d2256 100644 > --- a/drivers/video/fbdev/core/fbcon.c > +++ b/drivers/video/fbdev/core/fbcon.c > @@ -76,6 +76,7 @@ > #include <linux/crc32.h> /* For counting font checksums */ > #include <linux/uaccess.h> > #include <asm/irq.h> > +#include <asm/cmdline.h> > > #include "fbcon.h" > #include "fb_internal.h" > @@ -3358,6 +3359,26 @@ static int fbcon_output_notifier(struct notifier_block *nb, > > return NOTIFY_OK; > } > + > +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION > +static int initial_console; > +static struct notifier_block fbcon_switch_nb; > + > +static int fbcon_switch_notifier(struct notifier_block *nb, > + unsigned long action, void *data) > +{ > + struct vc_data *vc = data; > + > + WARN_CONSOLE_UNLOCKED(); > + > + if (vc->vc_num != initial_console) { > + dummycon_unregister_switch_notifier(&fbcon_switch_nb); > + dummycon_register_output_notifier(&fbcon_output_nb); > + } > + > + return NOTIFY_OK; > +} > +#endif > #endif > > static void fbcon_start(void) > @@ -3370,7 +3391,16 @@ static void fbcon_start(void) > > if (deferred_takeover) { > fbcon_output_nb.notifier_call = fbcon_output_notifier; > - dummycon_register_output_notifier(&fbcon_output_nb); > +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION > + if (cmdline_find_option_bool(boot_command_line, > + CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION)) { > + initial_console = fg_console; > + fbcon_switch_nb.notifier_call = fbcon_switch_notifier; > + dummycon_register_switch_notifier(&fbcon_switch_nb); > + } else > +#endif > + dummycon_register_output_notifier(&fbcon_output_nb); > + > return; > } > #endif > @@ -3417,8 +3447,12 @@ void __exit fb_console_exit(void) > { > #ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER > console_lock(); > - if (deferred_takeover) > + if (deferred_takeover) { > dummycon_unregister_output_notifier(&fbcon_output_nb); > +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION > + dummycon_unregister_switch_notifier(&fbcon_switch_nb); > +#endif > + } > console_unlock(); > > cancel_work_sync(&fbcon_deferred_takeover_work); > -- > 2.43.0 >
On 2/6/2024 08:21, Daniel Vetter wrote: > On Tue, Feb 06, 2024 at 06:10:51PM +0800, Daniel van Vugt wrote: >> Until now, deferred console takeover only meant defer until there is >> output. But that risks stepping on the toes of userspace splash screens, >> as console messages may appear before the splash screen. So check the >> command line for the expectation of userspace splash and if present then >> extend the deferral until after the first switch. >> >> V2: Added Kconfig option instead of hard coding "splash". >> >> Closes: https://bugs.launchpad.net/bugs/1970069 >> Cc: Mario Limonciello <mario.limonciello@amd.com> >> Signed-off-by: Daniel van Vugt <daniel.van.vugt@canonical.com> >> --- >> drivers/video/console/Kconfig | 13 +++++++++++ >> drivers/video/fbdev/core/fbcon.c | 38 ++++++++++++++++++++++++++++++-- >> 2 files changed, 49 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/video/console/Kconfig b/drivers/video/console/Kconfig >> index bc31db6ef7..a6e371bfb4 100644 >> --- a/drivers/video/console/Kconfig >> +++ b/drivers/video/console/Kconfig >> @@ -138,6 +138,19 @@ config FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER >> by the firmware in place, rather then replacing the contents with a >> black screen as soon as fbcon loads. >> >> +config FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION >> + string "Framebuffer Console Deferred Takeover Condition" >> + depends on FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER >> + default "splash" >> + help >> + If enabled this defers further the framebuffer console taking over >> + until the first console switch has occurred. And even then only if >> + text has been output, and only if the specified parameter is found >> + on the command line. This ensures fbcon does not interrupt userspace >> + splash screens such as Plymouth which may be yet to start rendering >> + at the time of the first console output. "splash" is the simplest >> + distro-agnostic condition for this that Plymouth checks for. > > Hm this seems a bit strange since a lot of complexity that no one needs, > also my impression is that it's rather distro specific how you want this > to work. So why not just a Kconfig option that lets you choose how much > you want to delay fbcon setup, with the following options: > > - no delay at all > - dely until first output from the console (which then works for distros > which set a log-level to suppress unwanted stuff) > - delay until first vt-switch. In that case I don't think we also need to > delay for first output, since vt switch usually means you'll get first > output right away (if it's a vt terminal) or you switch to a different > graphical console (which will keep fbcon fully suppressed on the drm > side). > IIUC there is an "automatic" VT switch that happens with Ubuntu GRUB + Ubuntu kernels. Why? Couldn't this also be suppressed by just not doing that? > I think you could even reuse the existing > CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER for this, and then just > compile-time select which kind of notifier to register (well plus the > check for "splash" on the cmdline for the vt switch one I guess). > > Thoughts? > > Cheers, Sima > > >> + >> config STI_CONSOLE >> bool "STI text console" >> depends on PARISC && HAS_IOMEM >> diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c >> index 63af6ab034..98155d2256 100644 >> --- a/drivers/video/fbdev/core/fbcon.c >> +++ b/drivers/video/fbdev/core/fbcon.c >> @@ -76,6 +76,7 @@ >> #include <linux/crc32.h> /* For counting font checksums */ >> #include <linux/uaccess.h> >> #include <asm/irq.h> >> +#include <asm/cmdline.h> >> >> #include "fbcon.h" >> #include "fb_internal.h" >> @@ -3358,6 +3359,26 @@ static int fbcon_output_notifier(struct notifier_block *nb, >> >> return NOTIFY_OK; >> } >> + >> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION >> +static int initial_console; >> +static struct notifier_block fbcon_switch_nb; >> + >> +static int fbcon_switch_notifier(struct notifier_block *nb, >> + unsigned long action, void *data) >> +{ >> + struct vc_data *vc = data; >> + >> + WARN_CONSOLE_UNLOCKED(); >> + >> + if (vc->vc_num != initial_console) { >> + dummycon_unregister_switch_notifier(&fbcon_switch_nb); >> + dummycon_register_output_notifier(&fbcon_output_nb); >> + } >> + >> + return NOTIFY_OK; >> +} >> +#endif >> #endif >> >> static void fbcon_start(void) >> @@ -3370,7 +3391,16 @@ static void fbcon_start(void) >> >> if (deferred_takeover) { >> fbcon_output_nb.notifier_call = fbcon_output_notifier; >> - dummycon_register_output_notifier(&fbcon_output_nb); >> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION >> + if (cmdline_find_option_bool(boot_command_line, >> + CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION)) { >> + initial_console = fg_console; >> + fbcon_switch_nb.notifier_call = fbcon_switch_notifier; >> + dummycon_register_switch_notifier(&fbcon_switch_nb); >> + } else >> +#endif >> + dummycon_register_output_notifier(&fbcon_output_nb); >> + >> return; >> } >> #endif >> @@ -3417,8 +3447,12 @@ void __exit fb_console_exit(void) >> { >> #ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER >> console_lock(); >> - if (deferred_takeover) >> + if (deferred_takeover) { >> dummycon_unregister_output_notifier(&fbcon_output_nb); >> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION >> + dummycon_unregister_switch_notifier(&fbcon_switch_nb); >> +#endif >> + } >> console_unlock(); >> >> cancel_work_sync(&fbcon_deferred_takeover_work); >> -- >> 2.43.0 >> >
On 6/2/24 23:41, Mario Limonciello wrote: > On 2/6/2024 08:21, Daniel Vetter wrote: >> On Tue, Feb 06, 2024 at 06:10:51PM +0800, Daniel van Vugt wrote: >>> Until now, deferred console takeover only meant defer until there is >>> output. But that risks stepping on the toes of userspace splash screens, >>> as console messages may appear before the splash screen. So check the >>> command line for the expectation of userspace splash and if present then >>> extend the deferral until after the first switch. >>> >>> V2: Added Kconfig option instead of hard coding "splash". >>> >>> Closes: https://bugs.launchpad.net/bugs/1970069 >>> Cc: Mario Limonciello <mario.limonciello@amd.com> >>> Signed-off-by: Daniel van Vugt <daniel.van.vugt@canonical.com> >>> --- >>> drivers/video/console/Kconfig | 13 +++++++++++ >>> drivers/video/fbdev/core/fbcon.c | 38 ++++++++++++++++++++++++++++++-- >>> 2 files changed, 49 insertions(+), 2 deletions(-) >>> >>> diff --git a/drivers/video/console/Kconfig b/drivers/video/console/Kconfig >>> index bc31db6ef7..a6e371bfb4 100644 >>> --- a/drivers/video/console/Kconfig >>> +++ b/drivers/video/console/Kconfig >>> @@ -138,6 +138,19 @@ config FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER >>> by the firmware in place, rather then replacing the contents with a >>> black screen as soon as fbcon loads. >>> +config FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION >>> + string "Framebuffer Console Deferred Takeover Condition" >>> + depends on FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER >>> + default "splash" >>> + help >>> + If enabled this defers further the framebuffer console taking over >>> + until the first console switch has occurred. And even then only if >>> + text has been output, and only if the specified parameter is found >>> + on the command line. This ensures fbcon does not interrupt userspace >>> + splash screens such as Plymouth which may be yet to start rendering >>> + at the time of the first console output. "splash" is the simplest >>> + distro-agnostic condition for this that Plymouth checks for. >> >> Hm this seems a bit strange since a lot of complexity that no one needs, >> also my impression is that it's rather distro specific how you want this >> to work. So why not just a Kconfig option that lets you choose how much >> you want to delay fbcon setup, with the following options: >> >> - no delay at all >> - dely until first output from the console (which then works for distros >> which set a log-level to suppress unwanted stuff) >> - delay until first vt-switch. In that case I don't think we also need to >> delay for first output, since vt switch usually means you'll get first >> output right away (if it's a vt terminal) or you switch to a different >> graphical console (which will keep fbcon fully suppressed on the drm >> side). >> I had similar thoughts, and had prototyped some of this already. But in the end it felt like extra complexity there was no demand for. If you would like to specify the preferred Kconfig design then I can implement it. Though I don't think there is an enumeration type. It could also be a runtime enumeration (deferred_takeover) controlled by fbcon=something. > > IIUC there is an "automatic" VT switch that happens with Ubuntu GRUB + Ubuntu > kernels. > > Why? > > Couldn't this also be suppressed by just not doing that? I have not seen any automatic VT switches in debugging but now that you mention it I was probably only debugging on drm-misc-next and not an Ubuntu kernel. - Daniel > >> I think you could even reuse the existing >> CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER for this, and then just >> compile-time select which kind of notifier to register (well plus the >> check for "splash" on the cmdline for the vt switch one I guess). >> >> Thoughts? >> >> Cheers, Sima >> >> >>> + >>> config STI_CONSOLE >>> bool "STI text console" >>> depends on PARISC && HAS_IOMEM >>> diff --git a/drivers/video/fbdev/core/fbcon.c >>> b/drivers/video/fbdev/core/fbcon.c >>> index 63af6ab034..98155d2256 100644 >>> --- a/drivers/video/fbdev/core/fbcon.c >>> +++ b/drivers/video/fbdev/core/fbcon.c >>> @@ -76,6 +76,7 @@ >>> #include <linux/crc32.h> /* For counting font checksums */ >>> #include <linux/uaccess.h> >>> #include <asm/irq.h> >>> +#include <asm/cmdline.h> >>> #include "fbcon.h" >>> #include "fb_internal.h" >>> @@ -3358,6 +3359,26 @@ static int fbcon_output_notifier(struct >>> notifier_block *nb, >>> return NOTIFY_OK; >>> } >>> + >>> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION >>> +static int initial_console; >>> +static struct notifier_block fbcon_switch_nb; >>> + >>> +static int fbcon_switch_notifier(struct notifier_block *nb, >>> + unsigned long action, void *data) >>> +{ >>> + struct vc_data *vc = data; >>> + >>> + WARN_CONSOLE_UNLOCKED(); >>> + >>> + if (vc->vc_num != initial_console) { >>> + dummycon_unregister_switch_notifier(&fbcon_switch_nb); >>> + dummycon_register_output_notifier(&fbcon_output_nb); >>> + } >>> + >>> + return NOTIFY_OK; >>> +} >>> +#endif >>> #endif >>> static void fbcon_start(void) >>> @@ -3370,7 +3391,16 @@ static void fbcon_start(void) >>> if (deferred_takeover) { >>> fbcon_output_nb.notifier_call = fbcon_output_notifier; >>> - dummycon_register_output_notifier(&fbcon_output_nb); >>> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION >>> + if (cmdline_find_option_bool(boot_command_line, >>> + CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION)) { >>> + initial_console = fg_console; >>> + fbcon_switch_nb.notifier_call = fbcon_switch_notifier; >>> + dummycon_register_switch_notifier(&fbcon_switch_nb); >>> + } else >>> +#endif >>> + dummycon_register_output_notifier(&fbcon_output_nb); >>> + >>> return; >>> } >>> #endif >>> @@ -3417,8 +3447,12 @@ void __exit fb_console_exit(void) >>> { >>> #ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER >>> console_lock(); >>> - if (deferred_takeover) >>> + if (deferred_takeover) { >>> dummycon_unregister_output_notifier(&fbcon_output_nb); >>> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION >>> + dummycon_unregister_switch_notifier(&fbcon_switch_nb); >>> +#endif >>> + } >>> console_unlock(); >>> cancel_work_sync(&fbcon_deferred_takeover_work); >>> -- >>> 2.43.0 >>> >> >
On Wed, Feb 07, 2024 at 10:03:10AM +0800, Daniel van Vugt wrote: > On 6/2/24 23:41, Mario Limonciello wrote: > > On 2/6/2024 08:21, Daniel Vetter wrote: > >> On Tue, Feb 06, 2024 at 06:10:51PM +0800, Daniel van Vugt wrote: > >>> Until now, deferred console takeover only meant defer until there is > >>> output. But that risks stepping on the toes of userspace splash screens, > >>> as console messages may appear before the splash screen. So check the > >>> command line for the expectation of userspace splash and if present then > >>> extend the deferral until after the first switch. > >>> > >>> V2: Added Kconfig option instead of hard coding "splash". > >>> > >>> Closes: https://bugs.launchpad.net/bugs/1970069 > >>> Cc: Mario Limonciello <mario.limonciello@amd.com> > >>> Signed-off-by: Daniel van Vugt <daniel.van.vugt@canonical.com> > >>> --- > >>> drivers/video/console/Kconfig | 13 +++++++++++ > >>> drivers/video/fbdev/core/fbcon.c | 38 ++++++++++++++++++++++++++++++-- > >>> 2 files changed, 49 insertions(+), 2 deletions(-) > >>> > >>> diff --git a/drivers/video/console/Kconfig b/drivers/video/console/Kconfig > >>> index bc31db6ef7..a6e371bfb4 100644 > >>> --- a/drivers/video/console/Kconfig > >>> +++ b/drivers/video/console/Kconfig > >>> @@ -138,6 +138,19 @@ config FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER > >>> by the firmware in place, rather then replacing the contents with a > >>> black screen as soon as fbcon loads. > >>> +config FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION > >>> + string "Framebuffer Console Deferred Takeover Condition" > >>> + depends on FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER > >>> + default "splash" > >>> + help > >>> + If enabled this defers further the framebuffer console taking over > >>> + until the first console switch has occurred. And even then only if > >>> + text has been output, and only if the specified parameter is found > >>> + on the command line. This ensures fbcon does not interrupt userspace > >>> + splash screens such as Plymouth which may be yet to start rendering > >>> + at the time of the first console output. "splash" is the simplest > >>> + distro-agnostic condition for this that Plymouth checks for. > >> > >> Hm this seems a bit strange since a lot of complexity that no one needs, > >> also my impression is that it's rather distro specific how you want this > >> to work. So why not just a Kconfig option that lets you choose how much > >> you want to delay fbcon setup, with the following options: > >> > >> - no delay at all > >> - dely until first output from the console (which then works for distros > >> which set a log-level to suppress unwanted stuff) > >> - delay until first vt-switch. In that case I don't think we also need to > >> delay for first output, since vt switch usually means you'll get first > >> output right away (if it's a vt terminal) or you switch to a different > >> graphical console (which will keep fbcon fully suppressed on the drm > >> side). > >> > > I had similar thoughts, and had prototyped some of this already. But in the end > it felt like extra complexity there was no demand for. For me this one is a bit too complex, since if you enable the vt switch delay you also get the output delay on top. That seems one too much and I can't come up with a use-case where you actually want that. So just a choice of one or the other or none feels cleaner. > If you would like to specify the preferred Kconfig design then I can implement > it. Though I don't think there is an enumeration type. It could also be a > runtime enumeration (deferred_takeover) controlled by fbcon=something. There's a choice in Kconfig, see e.g. kernel/Kconfig.hz for an example. > > IIUC there is an "automatic" VT switch that happens with Ubuntu GRUB + Ubuntu > > kernels. > > > > Why? > > > > Couldn't this also be suppressed by just not doing that? > > I have not seen any automatic VT switches in debugging but now that you mention > it I was probably only debugging on drm-misc-next and not an Ubuntu kernel. Hm but I don't see how the output delay would paper over a race (if there is one) reliable for this case? If you do vt switch for boot splash or login screen and don't yet have drm opened for display or something like that, then fbcon can sneak in anyway ... Cheers, Sima > > - Daniel > > > > >> I think you could even reuse the existing > >> CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER for this, and then just > >> compile-time select which kind of notifier to register (well plus the > >> check for "splash" on the cmdline for the vt switch one I guess). > >> > >> Thoughts? > >> > >> Cheers, Sima > >> > >> > >>> + > >>> config STI_CONSOLE > >>> bool "STI text console" > >>> depends on PARISC && HAS_IOMEM > >>> diff --git a/drivers/video/fbdev/core/fbcon.c > >>> b/drivers/video/fbdev/core/fbcon.c > >>> index 63af6ab034..98155d2256 100644 > >>> --- a/drivers/video/fbdev/core/fbcon.c > >>> +++ b/drivers/video/fbdev/core/fbcon.c > >>> @@ -76,6 +76,7 @@ > >>> #include <linux/crc32.h> /* For counting font checksums */ > >>> #include <linux/uaccess.h> > >>> #include <asm/irq.h> > >>> +#include <asm/cmdline.h> > >>> #include "fbcon.h" > >>> #include "fb_internal.h" > >>> @@ -3358,6 +3359,26 @@ static int fbcon_output_notifier(struct > >>> notifier_block *nb, > >>> return NOTIFY_OK; > >>> } > >>> + > >>> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION > >>> +static int initial_console; > >>> +static struct notifier_block fbcon_switch_nb; > >>> + > >>> +static int fbcon_switch_notifier(struct notifier_block *nb, > >>> + unsigned long action, void *data) > >>> +{ > >>> + struct vc_data *vc = data; > >>> + > >>> + WARN_CONSOLE_UNLOCKED(); > >>> + > >>> + if (vc->vc_num != initial_console) { > >>> + dummycon_unregister_switch_notifier(&fbcon_switch_nb); > >>> + dummycon_register_output_notifier(&fbcon_output_nb); > >>> + } > >>> + > >>> + return NOTIFY_OK; > >>> +} > >>> +#endif > >>> #endif > >>> static void fbcon_start(void) > >>> @@ -3370,7 +3391,16 @@ static void fbcon_start(void) > >>> if (deferred_takeover) { > >>> fbcon_output_nb.notifier_call = fbcon_output_notifier; > >>> - dummycon_register_output_notifier(&fbcon_output_nb); > >>> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION > >>> + if (cmdline_find_option_bool(boot_command_line, > >>> + CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION)) { > >>> + initial_console = fg_console; > >>> + fbcon_switch_nb.notifier_call = fbcon_switch_notifier; > >>> + dummycon_register_switch_notifier(&fbcon_switch_nb); > >>> + } else > >>> +#endif > >>> + dummycon_register_output_notifier(&fbcon_output_nb); > >>> + > >>> return; > >>> } > >>> #endif > >>> @@ -3417,8 +3447,12 @@ void __exit fb_console_exit(void) > >>> { > >>> #ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER > >>> console_lock(); > >>> - if (deferred_takeover) > >>> + if (deferred_takeover) { > >>> dummycon_unregister_output_notifier(&fbcon_output_nb); > >>> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION > >>> + dummycon_unregister_switch_notifier(&fbcon_switch_nb); > >>> +#endif > >>> + } > >>> console_unlock(); > >>> cancel_work_sync(&fbcon_deferred_takeover_work); > >>> -- > >>> 2.43.0 > >>> > >> > >
On 2/7/2024 03:51, Daniel Vetter wrote: > On Wed, Feb 07, 2024 at 10:03:10AM +0800, Daniel van Vugt wrote: >> On 6/2/24 23:41, Mario Limonciello wrote: >>> On 2/6/2024 08:21, Daniel Vetter wrote: >>>> On Tue, Feb 06, 2024 at 06:10:51PM +0800, Daniel van Vugt wrote: >>>>> Until now, deferred console takeover only meant defer until there is >>>>> output. But that risks stepping on the toes of userspace splash screens, >>>>> as console messages may appear before the splash screen. So check the >>>>> command line for the expectation of userspace splash and if present then >>>>> extend the deferral until after the first switch. >>>>> >>>>> V2: Added Kconfig option instead of hard coding "splash". >>>>> >>>>> Closes: https://bugs.launchpad.net/bugs/1970069 >>>>> Cc: Mario Limonciello <mario.limonciello@amd.com> >>>>> Signed-off-by: Daniel van Vugt <daniel.van.vugt@canonical.com> >>>>> --- >>>>> drivers/video/console/Kconfig | 13 +++++++++++ >>>>> drivers/video/fbdev/core/fbcon.c | 38 ++++++++++++++++++++++++++++++-- >>>>> 2 files changed, 49 insertions(+), 2 deletions(-) >>>>> >>>>> diff --git a/drivers/video/console/Kconfig b/drivers/video/console/Kconfig >>>>> index bc31db6ef7..a6e371bfb4 100644 >>>>> --- a/drivers/video/console/Kconfig >>>>> +++ b/drivers/video/console/Kconfig >>>>> @@ -138,6 +138,19 @@ config FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER >>>>> by the firmware in place, rather then replacing the contents with a >>>>> black screen as soon as fbcon loads. >>>>> +config FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION >>>>> + string "Framebuffer Console Deferred Takeover Condition" >>>>> + depends on FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER >>>>> + default "splash" >>>>> + help >>>>> + If enabled this defers further the framebuffer console taking over >>>>> + until the first console switch has occurred. And even then only if >>>>> + text has been output, and only if the specified parameter is found >>>>> + on the command line. This ensures fbcon does not interrupt userspace >>>>> + splash screens such as Plymouth which may be yet to start rendering >>>>> + at the time of the first console output. "splash" is the simplest >>>>> + distro-agnostic condition for this that Plymouth checks for. >>>> >>>> Hm this seems a bit strange since a lot of complexity that no one needs, >>>> also my impression is that it's rather distro specific how you want this >>>> to work. So why not just a Kconfig option that lets you choose how much >>>> you want to delay fbcon setup, with the following options: >>>> >>>> - no delay at all >>>> - dely until first output from the console (which then works for distros >>>> which set a log-level to suppress unwanted stuff) >>>> - delay until first vt-switch. In that case I don't think we also need to >>>> delay for first output, since vt switch usually means you'll get first >>>> output right away (if it's a vt terminal) or you switch to a different >>>> graphical console (which will keep fbcon fully suppressed on the drm >>>> side). >>>> >> >> I had similar thoughts, and had prototyped some of this already. But in the end >> it felt like extra complexity there was no demand for. > > For me this one is a bit too complex, since if you enable the vt switch > delay you also get the output delay on top. That seems one too much and I > can't come up with a use-case where you actually want that. So just a > choice of one or the other or none feels cleaner. > >> If you would like to specify the preferred Kconfig design then I can implement >> it. Though I don't think there is an enumeration type. It could also be a >> runtime enumeration (deferred_takeover) controlled by fbcon=something. > > There's a choice in Kconfig, see e.g. kernel/Kconfig.hz for an example. > >>> IIUC there is an "automatic" VT switch that happens with Ubuntu GRUB + Ubuntu >>> kernels. >>> >>> Why? >>> >>> Couldn't this also be suppressed by just not doing that? >> >> I have not seen any automatic VT switches in debugging but now that you mention >> it I was probably only debugging on drm-misc-next and not an Ubuntu kernel. > > Hm but I don't see how the output delay would paper over a race (if there > is one) reliable for this case? If you do vt switch for boot splash or > login screen and don't yet have drm opened for display or something like > that, then fbcon can sneak in anyway ... Ubuntu has had in (at least some) kernels: https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/unstable/commit/?id=320cfac8ef31 I'm unsure if it's still there today, but maybe it would be best if the author (Andy) could enlighten us? Any idea why that didn't go upstream? I had thought that tied with a automatic VT switch that was trying to hide fbcon as well. > > Cheers, Sima >> >> - Daniel >> >>> >>>> I think you could even reuse the existing >>>> CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER for this, and then just >>>> compile-time select which kind of notifier to register (well plus the >>>> check for "splash" on the cmdline for the vt switch one I guess). >>>> >>>> Thoughts? >>>> >>>> Cheers, Sima >>>> >>>> >>>>> + >>>>> config STI_CONSOLE >>>>> bool "STI text console" >>>>> depends on PARISC && HAS_IOMEM >>>>> diff --git a/drivers/video/fbdev/core/fbcon.c >>>>> b/drivers/video/fbdev/core/fbcon.c >>>>> index 63af6ab034..98155d2256 100644 >>>>> --- a/drivers/video/fbdev/core/fbcon.c >>>>> +++ b/drivers/video/fbdev/core/fbcon.c >>>>> @@ -76,6 +76,7 @@ >>>>> #include <linux/crc32.h> /* For counting font checksums */ >>>>> #include <linux/uaccess.h> >>>>> #include <asm/irq.h> >>>>> +#include <asm/cmdline.h> >>>>> #include "fbcon.h" >>>>> #include "fb_internal.h" >>>>> @@ -3358,6 +3359,26 @@ static int fbcon_output_notifier(struct >>>>> notifier_block *nb, >>>>> return NOTIFY_OK; >>>>> } >>>>> + >>>>> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION >>>>> +static int initial_console; >>>>> +static struct notifier_block fbcon_switch_nb; >>>>> + >>>>> +static int fbcon_switch_notifier(struct notifier_block *nb, >>>>> + unsigned long action, void *data) >>>>> +{ >>>>> + struct vc_data *vc = data; >>>>> + >>>>> + WARN_CONSOLE_UNLOCKED(); >>>>> + >>>>> + if (vc->vc_num != initial_console) { >>>>> + dummycon_unregister_switch_notifier(&fbcon_switch_nb); >>>>> + dummycon_register_output_notifier(&fbcon_output_nb); >>>>> + } >>>>> + >>>>> + return NOTIFY_OK; >>>>> +} >>>>> +#endif >>>>> #endif >>>>> static void fbcon_start(void) >>>>> @@ -3370,7 +3391,16 @@ static void fbcon_start(void) >>>>> if (deferred_takeover) { >>>>> fbcon_output_nb.notifier_call = fbcon_output_notifier; >>>>> - dummycon_register_output_notifier(&fbcon_output_nb); >>>>> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION >>>>> + if (cmdline_find_option_bool(boot_command_line, >>>>> + CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION)) { >>>>> + initial_console = fg_console; >>>>> + fbcon_switch_nb.notifier_call = fbcon_switch_notifier; >>>>> + dummycon_register_switch_notifier(&fbcon_switch_nb); >>>>> + } else >>>>> +#endif >>>>> + dummycon_register_output_notifier(&fbcon_output_nb); >>>>> + >>>>> return; >>>>> } >>>>> #endif >>>>> @@ -3417,8 +3447,12 @@ void __exit fb_console_exit(void) >>>>> { >>>>> #ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER >>>>> console_lock(); >>>>> - if (deferred_takeover) >>>>> + if (deferred_takeover) { >>>>> dummycon_unregister_output_notifier(&fbcon_output_nb); >>>>> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION >>>>> + dummycon_unregister_switch_notifier(&fbcon_switch_nb); >>>>> +#endif >>>>> + } >>>>> console_unlock(); >>>>> cancel_work_sync(&fbcon_deferred_takeover_work); >>>>> -- >>>>> 2.43.0 >>>>> >>>> >>> >
On 8/2/24 04:21, Mario Limonciello wrote: > On 2/7/2024 03:51, Daniel Vetter wrote: >> On Wed, Feb 07, 2024 at 10:03:10AM +0800, Daniel van Vugt wrote: >>> On 6/2/24 23:41, Mario Limonciello wrote: >>>> On 2/6/2024 08:21, Daniel Vetter wrote: >>>>> On Tue, Feb 06, 2024 at 06:10:51PM +0800, Daniel van Vugt wrote: >>>>>> Until now, deferred console takeover only meant defer until there is >>>>>> output. But that risks stepping on the toes of userspace splash screens, >>>>>> as console messages may appear before the splash screen. So check the >>>>>> command line for the expectation of userspace splash and if present then >>>>>> extend the deferral until after the first switch. >>>>>> >>>>>> V2: Added Kconfig option instead of hard coding "splash". >>>>>> >>>>>> Closes: https://bugs.launchpad.net/bugs/1970069 >>>>>> Cc: Mario Limonciello <mario.limonciello@amd.com> >>>>>> Signed-off-by: Daniel van Vugt <daniel.van.vugt@canonical.com> >>>>>> --- >>>>>> drivers/video/console/Kconfig | 13 +++++++++++ >>>>>> drivers/video/fbdev/core/fbcon.c | 38 ++++++++++++++++++++++++++++++-- >>>>>> 2 files changed, 49 insertions(+), 2 deletions(-) >>>>>> >>>>>> diff --git a/drivers/video/console/Kconfig b/drivers/video/console/Kconfig >>>>>> index bc31db6ef7..a6e371bfb4 100644 >>>>>> --- a/drivers/video/console/Kconfig >>>>>> +++ b/drivers/video/console/Kconfig >>>>>> @@ -138,6 +138,19 @@ config FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER >>>>>> by the firmware in place, rather then replacing the contents with a >>>>>> black screen as soon as fbcon loads. >>>>>> +config FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION >>>>>> + string "Framebuffer Console Deferred Takeover Condition" >>>>>> + depends on FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER >>>>>> + default "splash" >>>>>> + help >>>>>> + If enabled this defers further the framebuffer console taking over >>>>>> + until the first console switch has occurred. And even then only if >>>>>> + text has been output, and only if the specified parameter is found >>>>>> + on the command line. This ensures fbcon does not interrupt userspace >>>>>> + splash screens such as Plymouth which may be yet to start rendering >>>>>> + at the time of the first console output. "splash" is the simplest >>>>>> + distro-agnostic condition for this that Plymouth checks for. >>>>> >>>>> Hm this seems a bit strange since a lot of complexity that no one needs, >>>>> also my impression is that it's rather distro specific how you want this >>>>> to work. So why not just a Kconfig option that lets you choose how much >>>>> you want to delay fbcon setup, with the following options: >>>>> >>>>> - no delay at all >>>>> - dely until first output from the console (which then works for distros >>>>> which set a log-level to suppress unwanted stuff) >>>>> - delay until first vt-switch. In that case I don't think we also need to >>>>> delay for first output, since vt switch usually means you'll get first >>>>> output right away (if it's a vt terminal) or you switch to a different >>>>> graphical console (which will keep fbcon fully suppressed on the drm >>>>> side). >>>>> >>> >>> I had similar thoughts, and had prototyped some of this already. But in the end >>> it felt like extra complexity there was no demand for. >> >> For me this one is a bit too complex, since if you enable the vt switch >> delay you also get the output delay on top. That seems one too much and I >> can't come up with a use-case where you actually want that. So just a >> choice of one or the other or none feels cleaner. Remember the output "delay" goes to zero if any putc has occurred prior to registration (see dummycon.c). My current reason for using both is that in theory it prevents fbcon from taking over *earlier* than it did before, in case there was never any output. But I don't think there is "never any output" by the time you've tried to manually VT switch so maybe that's unnecessary. >> >>> If you would like to specify the preferred Kconfig design then I can implement >>> it. Though I don't think there is an enumeration type. It could also be a >>> runtime enumeration (deferred_takeover) controlled by fbcon=something. >> >> There's a choice in Kconfig, see e.g. kernel/Kconfig.hz for an example. Thanks! >> >>>> IIUC there is an "automatic" VT switch that happens with Ubuntu GRUB + Ubuntu >>>> kernels. >>>> >>>> Why? >>>> >>>> Couldn't this also be suppressed by just not doing that? >>> >>> I have not seen any automatic VT switches in debugging but now that you mention >>> it I was probably only debugging on drm-misc-next and not an Ubuntu kernel. >> >> Hm but I don't see how the output delay would paper over a race (if there >> is one) reliable for this case? If you do vt switch for boot splash or >> login screen and don't yet have drm opened for display or something like >> that, then fbcon can sneak in anyway ... There is no VT switch according to my logs, so there is no race with the patchset. The only race that occurs is without this patchset, which is what's being fixed here. > > Ubuntu has had in (at least some) kernels: > > https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/unstable/commit/?id=320cfac8ef31 > > I'm unsure if it's still there today, but maybe it would be best if the author > (Andy) could enlighten us? Any idea why that didn't go upstream? > > I had thought that tied with a automatic VT switch that was trying to hide > fbcon as well. I checked the current Ubuntu 24.04 kernel yesterday and there is no VT switch (anymore). The vc_num stays at zero until you do a manual VT switch. This seems to be true for both drm-misc-next and Ubuntu kernels. There is still vt.handoff=7 on the command line for Ubuntu, but I'm not sure it has a function anymore. Maybe it was primarily for legacy BIOS? Andy can confirm. > >> >> Cheers, Sima >>> >>> - Daniel >>> >>>> >>>>> I think you could even reuse the existing >>>>> CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER for this, and then just >>>>> compile-time select which kind of notifier to register (well plus the >>>>> check for "splash" on the cmdline for the vt switch one I guess). >>>>> >>>>> Thoughts? >>>>> >>>>> Cheers, Sima >>>>> >>>>> >>>>>> + >>>>>> config STI_CONSOLE >>>>>> bool "STI text console" >>>>>> depends on PARISC && HAS_IOMEM >>>>>> diff --git a/drivers/video/fbdev/core/fbcon.c >>>>>> b/drivers/video/fbdev/core/fbcon.c >>>>>> index 63af6ab034..98155d2256 100644 >>>>>> --- a/drivers/video/fbdev/core/fbcon.c >>>>>> +++ b/drivers/video/fbdev/core/fbcon.c >>>>>> @@ -76,6 +76,7 @@ >>>>>> #include <linux/crc32.h> /* For counting font checksums */ >>>>>> #include <linux/uaccess.h> >>>>>> #include <asm/irq.h> >>>>>> +#include <asm/cmdline.h> >>>>>> #include "fbcon.h" >>>>>> #include "fb_internal.h" >>>>>> @@ -3358,6 +3359,26 @@ static int fbcon_output_notifier(struct >>>>>> notifier_block *nb, >>>>>> return NOTIFY_OK; >>>>>> } >>>>>> + >>>>>> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION >>>>>> +static int initial_console; >>>>>> +static struct notifier_block fbcon_switch_nb; >>>>>> + >>>>>> +static int fbcon_switch_notifier(struct notifier_block *nb, >>>>>> + unsigned long action, void *data) >>>>>> +{ >>>>>> + struct vc_data *vc = data; >>>>>> + >>>>>> + WARN_CONSOLE_UNLOCKED(); >>>>>> + >>>>>> + if (vc->vc_num != initial_console) { >>>>>> + dummycon_unregister_switch_notifier(&fbcon_switch_nb); >>>>>> + dummycon_register_output_notifier(&fbcon_output_nb); >>>>>> + } >>>>>> + >>>>>> + return NOTIFY_OK; >>>>>> +} >>>>>> +#endif >>>>>> #endif >>>>>> static void fbcon_start(void) >>>>>> @@ -3370,7 +3391,16 @@ static void fbcon_start(void) >>>>>> if (deferred_takeover) { >>>>>> fbcon_output_nb.notifier_call = fbcon_output_notifier; >>>>>> - dummycon_register_output_notifier(&fbcon_output_nb); >>>>>> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION >>>>>> + if (cmdline_find_option_bool(boot_command_line, >>>>>> + CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION)) { >>>>>> + initial_console = fg_console; >>>>>> + fbcon_switch_nb.notifier_call = fbcon_switch_notifier; >>>>>> + dummycon_register_switch_notifier(&fbcon_switch_nb); >>>>>> + } else >>>>>> +#endif >>>>>> + dummycon_register_output_notifier(&fbcon_output_nb); >>>>>> + >>>>>> return; >>>>>> } >>>>>> #endif >>>>>> @@ -3417,8 +3447,12 @@ void __exit fb_console_exit(void) >>>>>> { >>>>>> #ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER >>>>>> console_lock(); >>>>>> - if (deferred_takeover) >>>>>> + if (deferred_takeover) { >>>>>> dummycon_unregister_output_notifier(&fbcon_output_nb); >>>>>> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION >>>>>> + dummycon_unregister_switch_notifier(&fbcon_switch_nb); >>>>>> +#endif >>>>>> + } >>>>>> console_unlock(); >>>>>> cancel_work_sync(&fbcon_deferred_takeover_work); >>>>>> -- >>>>>> 2.43.0 >>>>>> >>>>> >>>> >> >
On Thu, Feb 08, 2024 at 09:16:50AM +0800, Daniel van Vugt wrote: > On 8/2/24 04:21, Mario Limonciello wrote: > > On 2/7/2024 03:51, Daniel Vetter wrote: > >> On Wed, Feb 07, 2024 at 10:03:10AM +0800, Daniel van Vugt wrote: > >>> On 6/2/24 23:41, Mario Limonciello wrote: > >>>> On 2/6/2024 08:21, Daniel Vetter wrote: > >>>>> On Tue, Feb 06, 2024 at 06:10:51PM +0800, Daniel van Vugt wrote: > >>>>>> Until now, deferred console takeover only meant defer until there is > >>>>>> output. But that risks stepping on the toes of userspace splash screens, > >>>>>> as console messages may appear before the splash screen. So check the > >>>>>> command line for the expectation of userspace splash and if present then > >>>>>> extend the deferral until after the first switch. > >>>>>> > >>>>>> V2: Added Kconfig option instead of hard coding "splash". > >>>>>> > >>>>>> Closes: https://bugs.launchpad.net/bugs/1970069 > >>>>>> Cc: Mario Limonciello <mario.limonciello@amd.com> > >>>>>> Signed-off-by: Daniel van Vugt <daniel.van.vugt@canonical.com> > >>>>>> --- > >>>>>> drivers/video/console/Kconfig | 13 +++++++++++ > >>>>>> drivers/video/fbdev/core/fbcon.c | 38 ++++++++++++++++++++++++++++++-- > >>>>>> 2 files changed, 49 insertions(+), 2 deletions(-) > >>>>>> > >>>>>> diff --git a/drivers/video/console/Kconfig b/drivers/video/console/Kconfig > >>>>>> index bc31db6ef7..a6e371bfb4 100644 > >>>>>> --- a/drivers/video/console/Kconfig > >>>>>> +++ b/drivers/video/console/Kconfig > >>>>>> @@ -138,6 +138,19 @@ config FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER > >>>>>> by the firmware in place, rather then replacing the contents with a > >>>>>> black screen as soon as fbcon loads. > >>>>>> +config FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION > >>>>>> + string "Framebuffer Console Deferred Takeover Condition" > >>>>>> + depends on FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER > >>>>>> + default "splash" > >>>>>> + help > >>>>>> + If enabled this defers further the framebuffer console taking over > >>>>>> + until the first console switch has occurred. And even then only if > >>>>>> + text has been output, and only if the specified parameter is found > >>>>>> + on the command line. This ensures fbcon does not interrupt userspace > >>>>>> + splash screens such as Plymouth which may be yet to start rendering > >>>>>> + at the time of the first console output. "splash" is the simplest > >>>>>> + distro-agnostic condition for this that Plymouth checks for. > >>>>> > >>>>> Hm this seems a bit strange since a lot of complexity that no one needs, > >>>>> also my impression is that it's rather distro specific how you want this > >>>>> to work. So why not just a Kconfig option that lets you choose how much > >>>>> you want to delay fbcon setup, with the following options: > >>>>> > >>>>> - no delay at all > >>>>> - dely until first output from the console (which then works for distros > >>>>> which set a log-level to suppress unwanted stuff) > >>>>> - delay until first vt-switch. In that case I don't think we also need to > >>>>> delay for first output, since vt switch usually means you'll get first > >>>>> output right away (if it's a vt terminal) or you switch to a different > >>>>> graphical console (which will keep fbcon fully suppressed on the drm > >>>>> side). > >>>>> > >>> > >>> I had similar thoughts, and had prototyped some of this already. But in the end > >>> it felt like extra complexity there was no demand for. > >> > >> For me this one is a bit too complex, since if you enable the vt switch > >> delay you also get the output delay on top. That seems one too much and I > >> can't come up with a use-case where you actually want that. So just a > >> choice of one or the other or none feels cleaner. > > Remember the output "delay" goes to zero if any putc has occurred prior to > registration (see dummycon.c). > > My current reason for using both is that in theory it prevents fbcon from > taking over *earlier* than it did before, in case there was never any output. > But I don't think there is "never any output" by the time you've tried to > manually VT switch so maybe that's unnecessary. Yeah, but I'm not sure that's like a choice anyone needs, just these three: - no delay - wait until first output, and set debuglevel appropriately (what fedora and other distros do) - wait until first vt switch (what ubuntu wants) I don't ever expect fedora to just enable this, because they have something that works. Plus many distros are moving away from CONFIG_VT and all the in-kernel consoles anyway, so they want this even less. So if just the delay to first vt-switch is enough for you, I think it's best we just implement that. The entire vt switch/ownership rules with drm and fbdev and all that is already really complex and in many cases it's impossible to tell what's accidental cargo-culted behaviour and what is actually required. That's why I'd prefer we exactly implement what you need in this area, nothing more, nothing less. And from the testing you discuss below it sounds like you don't need both delays? Cheers, Sima > >>> If you would like to specify the preferred Kconfig design then I can implement > >>> it. Though I don't think there is an enumeration type. It could also be a > >>> runtime enumeration (deferred_takeover) controlled by fbcon=something. > >> > >> There's a choice in Kconfig, see e.g. kernel/Kconfig.hz for an example. > > Thanks! > > >> > >>>> IIUC there is an "automatic" VT switch that happens with Ubuntu GRUB + Ubuntu > >>>> kernels. > >>>> > >>>> Why? > >>>> > >>>> Couldn't this also be suppressed by just not doing that? > >>> > >>> I have not seen any automatic VT switches in debugging but now that you mention > >>> it I was probably only debugging on drm-misc-next and not an Ubuntu kernel. > >> > >> Hm but I don't see how the output delay would paper over a race (if there > >> is one) reliable for this case? If you do vt switch for boot splash or > >> login screen and don't yet have drm opened for display or something like > >> that, then fbcon can sneak in anyway ... > > There is no VT switch according to my logs, so there is no race with the > patchset. The only race that occurs is without this patchset, which is what's > being fixed here. > > > > > Ubuntu has had in (at least some) kernels: > > > > https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/unstable/commit/?id=320cfac8ef31 > > > > I'm unsure if it's still there today, but maybe it would be best if the author > > (Andy) could enlighten us? Any idea why that didn't go upstream? > > > > I had thought that tied with a automatic VT switch that was trying to hide > > fbcon as well. > > I checked the current Ubuntu 24.04 kernel yesterday and there is no VT switch > (anymore). The vc_num stays at zero until you do a manual VT switch. This seems > to be true for both drm-misc-next and Ubuntu kernels. > > There is still vt.handoff=7 on the command line for Ubuntu, but I'm not sure it > has a function anymore. Maybe it was primarily for legacy BIOS? Andy can confirm. > > > > >> > >> Cheers, Sima > >>> > >>> - Daniel > >>> > >>>> > >>>>> I think you could even reuse the existing > >>>>> CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER for this, and then just > >>>>> compile-time select which kind of notifier to register (well plus the > >>>>> check for "splash" on the cmdline for the vt switch one I guess). > >>>>> > >>>>> Thoughts? > >>>>> > >>>>> Cheers, Sima > >>>>> > >>>>> > >>>>>> + > >>>>>> config STI_CONSOLE > >>>>>> bool "STI text console" > >>>>>> depends on PARISC && HAS_IOMEM > >>>>>> diff --git a/drivers/video/fbdev/core/fbcon.c > >>>>>> b/drivers/video/fbdev/core/fbcon.c > >>>>>> index 63af6ab034..98155d2256 100644 > >>>>>> --- a/drivers/video/fbdev/core/fbcon.c > >>>>>> +++ b/drivers/video/fbdev/core/fbcon.c > >>>>>> @@ -76,6 +76,7 @@ > >>>>>> #include <linux/crc32.h> /* For counting font checksums */ > >>>>>> #include <linux/uaccess.h> > >>>>>> #include <asm/irq.h> > >>>>>> +#include <asm/cmdline.h> > >>>>>> #include "fbcon.h" > >>>>>> #include "fb_internal.h" > >>>>>> @@ -3358,6 +3359,26 @@ static int fbcon_output_notifier(struct > >>>>>> notifier_block *nb, > >>>>>> return NOTIFY_OK; > >>>>>> } > >>>>>> + > >>>>>> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION > >>>>>> +static int initial_console; > >>>>>> +static struct notifier_block fbcon_switch_nb; > >>>>>> + > >>>>>> +static int fbcon_switch_notifier(struct notifier_block *nb, > >>>>>> + unsigned long action, void *data) > >>>>>> +{ > >>>>>> + struct vc_data *vc = data; > >>>>>> + > >>>>>> + WARN_CONSOLE_UNLOCKED(); > >>>>>> + > >>>>>> + if (vc->vc_num != initial_console) { > >>>>>> + dummycon_unregister_switch_notifier(&fbcon_switch_nb); > >>>>>> + dummycon_register_output_notifier(&fbcon_output_nb); > >>>>>> + } > >>>>>> + > >>>>>> + return NOTIFY_OK; > >>>>>> +} > >>>>>> +#endif > >>>>>> #endif > >>>>>> static void fbcon_start(void) > >>>>>> @@ -3370,7 +3391,16 @@ static void fbcon_start(void) > >>>>>> if (deferred_takeover) { > >>>>>> fbcon_output_nb.notifier_call = fbcon_output_notifier; > >>>>>> - dummycon_register_output_notifier(&fbcon_output_nb); > >>>>>> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION > >>>>>> + if (cmdline_find_option_bool(boot_command_line, > >>>>>> + CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION)) { > >>>>>> + initial_console = fg_console; > >>>>>> + fbcon_switch_nb.notifier_call = fbcon_switch_notifier; > >>>>>> + dummycon_register_switch_notifier(&fbcon_switch_nb); > >>>>>> + } else > >>>>>> +#endif > >>>>>> + dummycon_register_output_notifier(&fbcon_output_nb); > >>>>>> + > >>>>>> return; > >>>>>> } > >>>>>> #endif > >>>>>> @@ -3417,8 +3447,12 @@ void __exit fb_console_exit(void) > >>>>>> { > >>>>>> #ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER > >>>>>> console_lock(); > >>>>>> - if (deferred_takeover) > >>>>>> + if (deferred_takeover) { > >>>>>> dummycon_unregister_output_notifier(&fbcon_output_nb); > >>>>>> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION > >>>>>> + dummycon_unregister_switch_notifier(&fbcon_switch_nb); > >>>>>> +#endif > >>>>>> + } > >>>>>> console_unlock(); > >>>>>> cancel_work_sync(&fbcon_deferred_takeover_work); > >>>>>> -- > >>>>>> 2.43.0 > >>>>>> > >>>>> > >>>> > >> > >
On 9/2/24 18:58, Daniel Vetter wrote: > On Thu, Feb 08, 2024 at 09:16:50AM +0800, Daniel van Vugt wrote: >> On 8/2/24 04:21, Mario Limonciello wrote: >>> On 2/7/2024 03:51, Daniel Vetter wrote: >>>> On Wed, Feb 07, 2024 at 10:03:10AM +0800, Daniel van Vugt wrote: >>>>> On 6/2/24 23:41, Mario Limonciello wrote: >>>>>> On 2/6/2024 08:21, Daniel Vetter wrote: >>>>>>> On Tue, Feb 06, 2024 at 06:10:51PM +0800, Daniel van Vugt wrote: >>>>>>>> Until now, deferred console takeover only meant defer until there is >>>>>>>> output. But that risks stepping on the toes of userspace splash screens, >>>>>>>> as console messages may appear before the splash screen. So check the >>>>>>>> command line for the expectation of userspace splash and if present then >>>>>>>> extend the deferral until after the first switch. >>>>>>>> >>>>>>>> V2: Added Kconfig option instead of hard coding "splash". >>>>>>>> >>>>>>>> Closes: https://bugs.launchpad.net/bugs/1970069 >>>>>>>> Cc: Mario Limonciello <mario.limonciello@amd.com> >>>>>>>> Signed-off-by: Daniel van Vugt <daniel.van.vugt@canonical.com> >>>>>>>> --- >>>>>>>> drivers/video/console/Kconfig | 13 +++++++++++ >>>>>>>> drivers/video/fbdev/core/fbcon.c | 38 ++++++++++++++++++++++++++++++-- >>>>>>>> 2 files changed, 49 insertions(+), 2 deletions(-) >>>>>>>> >>>>>>>> diff --git a/drivers/video/console/Kconfig b/drivers/video/console/Kconfig >>>>>>>> index bc31db6ef7..a6e371bfb4 100644 >>>>>>>> --- a/drivers/video/console/Kconfig >>>>>>>> +++ b/drivers/video/console/Kconfig >>>>>>>> @@ -138,6 +138,19 @@ config FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER >>>>>>>> by the firmware in place, rather then replacing the contents with a >>>>>>>> black screen as soon as fbcon loads. >>>>>>>> +config FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION >>>>>>>> + string "Framebuffer Console Deferred Takeover Condition" >>>>>>>> + depends on FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER >>>>>>>> + default "splash" >>>>>>>> + help >>>>>>>> + If enabled this defers further the framebuffer console taking over >>>>>>>> + until the first console switch has occurred. And even then only if >>>>>>>> + text has been output, and only if the specified parameter is found >>>>>>>> + on the command line. This ensures fbcon does not interrupt userspace >>>>>>>> + splash screens such as Plymouth which may be yet to start rendering >>>>>>>> + at the time of the first console output. "splash" is the simplest >>>>>>>> + distro-agnostic condition for this that Plymouth checks for. >>>>>>> >>>>>>> Hm this seems a bit strange since a lot of complexity that no one needs, >>>>>>> also my impression is that it's rather distro specific how you want this >>>>>>> to work. So why not just a Kconfig option that lets you choose how much >>>>>>> you want to delay fbcon setup, with the following options: >>>>>>> >>>>>>> - no delay at all >>>>>>> - dely until first output from the console (which then works for distros >>>>>>> which set a log-level to suppress unwanted stuff) >>>>>>> - delay until first vt-switch. In that case I don't think we also need to >>>>>>> delay for first output, since vt switch usually means you'll get first >>>>>>> output right away (if it's a vt terminal) or you switch to a different >>>>>>> graphical console (which will keep fbcon fully suppressed on the drm >>>>>>> side). >>>>>>> >>>>> >>>>> I had similar thoughts, and had prototyped some of this already. But in the end >>>>> it felt like extra complexity there was no demand for. >>>> >>>> For me this one is a bit too complex, since if you enable the vt switch >>>> delay you also get the output delay on top. That seems one too much and I >>>> can't come up with a use-case where you actually want that. So just a >>>> choice of one or the other or none feels cleaner. >> >> Remember the output "delay" goes to zero if any putc has occurred prior to >> registration (see dummycon.c). >> >> My current reason for using both is that in theory it prevents fbcon from >> taking over *earlier* than it did before, in case there was never any output. >> But I don't think there is "never any output" by the time you've tried to >> manually VT switch so maybe that's unnecessary. > > Yeah, but I'm not sure that's like a choice anyone needs, just these > three: > > - no delay > - wait until first output, and set debuglevel appropriately (what fedora > and other distros do) > - wait until first vt switch (what ubuntu wants) Come to think of it, an enum or Kconfig "choice" isn't necessary if I change the default for CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION to blank/disabled. Then the default behaviour is unchanged and you've still got the choice of all three modes: - No delay: fbcon=nodefer - Wait until first output: Already happens when CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION is absent from the command line. - Wait until first VT switch: Would only happen if compiled with CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION and its value is present on the command line. P.S. I suspect Fedora and other distros are not immune to the problem, just make it less likely by starting Plymouth super early on simpledrm. Certainly I am finding some models of laptop emit kernel messages that would still pass under a reduced loglevel. > > I don't ever expect fedora to just enable this, because they have > something that works. Plus many distros are moving away from CONFIG_VT and > all the in-kernel consoles anyway, so they want this even less. > > So if just the delay to first vt-switch is enough for you, I think it's > best we just implement that. The entire vt switch/ownership rules with drm > and fbdev and all that is already really complex and in many cases it's > impossible to tell what's accidental cargo-culted behaviour and what is > actually required. That's why I'd prefer we exactly implement what you > need in this area, nothing more, nothing less. > > And from the testing you discuss below it sounds like you don't need both > delays? > > Cheers, Sima > >>>>> If you would like to specify the preferred Kconfig design then I can implement >>>>> it. Though I don't think there is an enumeration type. It could also be a >>>>> runtime enumeration (deferred_takeover) controlled by fbcon=something. >>>> >>>> There's a choice in Kconfig, see e.g. kernel/Kconfig.hz for an example. >> >> Thanks! >> >>>> >>>>>> IIUC there is an "automatic" VT switch that happens with Ubuntu GRUB + Ubuntu >>>>>> kernels. >>>>>> >>>>>> Why? >>>>>> >>>>>> Couldn't this also be suppressed by just not doing that? >>>>> >>>>> I have not seen any automatic VT switches in debugging but now that you mention >>>>> it I was probably only debugging on drm-misc-next and not an Ubuntu kernel. >>>> >>>> Hm but I don't see how the output delay would paper over a race (if there >>>> is one) reliable for this case? If you do vt switch for boot splash or >>>> login screen and don't yet have drm opened for display or something like >>>> that, then fbcon can sneak in anyway ... >> >> There is no VT switch according to my logs, so there is no race with the >> patchset. The only race that occurs is without this patchset, which is what's >> being fixed here. >> >>> >>> Ubuntu has had in (at least some) kernels: >>> >>> https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/unstable/commit/?id=320cfac8ef31 >>> >>> I'm unsure if it's still there today, but maybe it would be best if the author >>> (Andy) could enlighten us? Any idea why that didn't go upstream? >>> >>> I had thought that tied with a automatic VT switch that was trying to hide >>> fbcon as well. >> >> I checked the current Ubuntu 24.04 kernel yesterday and there is no VT switch >> (anymore). The vc_num stays at zero until you do a manual VT switch. This seems >> to be true for both drm-misc-next and Ubuntu kernels. >> >> There is still vt.handoff=7 on the command line for Ubuntu, but I'm not sure it >> has a function anymore. Maybe it was primarily for legacy BIOS? Andy can confirm. >> >>> >>>> >>>> Cheers, Sima >>>>> >>>>> - Daniel >>>>> >>>>>> >>>>>>> I think you could even reuse the existing >>>>>>> CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER for this, and then just >>>>>>> compile-time select which kind of notifier to register (well plus the >>>>>>> check for "splash" on the cmdline for the vt switch one I guess). >>>>>>> >>>>>>> Thoughts? >>>>>>> >>>>>>> Cheers, Sima >>>>>>> >>>>>>> >>>>>>>> + >>>>>>>> config STI_CONSOLE >>>>>>>> bool "STI text console" >>>>>>>> depends on PARISC && HAS_IOMEM >>>>>>>> diff --git a/drivers/video/fbdev/core/fbcon.c >>>>>>>> b/drivers/video/fbdev/core/fbcon.c >>>>>>>> index 63af6ab034..98155d2256 100644 >>>>>>>> --- a/drivers/video/fbdev/core/fbcon.c >>>>>>>> +++ b/drivers/video/fbdev/core/fbcon.c >>>>>>>> @@ -76,6 +76,7 @@ >>>>>>>> #include <linux/crc32.h> /* For counting font checksums */ >>>>>>>> #include <linux/uaccess.h> >>>>>>>> #include <asm/irq.h> >>>>>>>> +#include <asm/cmdline.h> >>>>>>>> #include "fbcon.h" >>>>>>>> #include "fb_internal.h" >>>>>>>> @@ -3358,6 +3359,26 @@ static int fbcon_output_notifier(struct >>>>>>>> notifier_block *nb, >>>>>>>> return NOTIFY_OK; >>>>>>>> } >>>>>>>> + >>>>>>>> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION >>>>>>>> +static int initial_console; >>>>>>>> +static struct notifier_block fbcon_switch_nb; >>>>>>>> + >>>>>>>> +static int fbcon_switch_notifier(struct notifier_block *nb, >>>>>>>> + unsigned long action, void *data) >>>>>>>> +{ >>>>>>>> + struct vc_data *vc = data; >>>>>>>> + >>>>>>>> + WARN_CONSOLE_UNLOCKED(); >>>>>>>> + >>>>>>>> + if (vc->vc_num != initial_console) { >>>>>>>> + dummycon_unregister_switch_notifier(&fbcon_switch_nb); >>>>>>>> + dummycon_register_output_notifier(&fbcon_output_nb); >>>>>>>> + } >>>>>>>> + >>>>>>>> + return NOTIFY_OK; >>>>>>>> +} >>>>>>>> +#endif >>>>>>>> #endif >>>>>>>> static void fbcon_start(void) >>>>>>>> @@ -3370,7 +3391,16 @@ static void fbcon_start(void) >>>>>>>> if (deferred_takeover) { >>>>>>>> fbcon_output_nb.notifier_call = fbcon_output_notifier; >>>>>>>> - dummycon_register_output_notifier(&fbcon_output_nb); >>>>>>>> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION >>>>>>>> + if (cmdline_find_option_bool(boot_command_line, >>>>>>>> + CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION)) { >>>>>>>> + initial_console = fg_console; >>>>>>>> + fbcon_switch_nb.notifier_call = fbcon_switch_notifier; >>>>>>>> + dummycon_register_switch_notifier(&fbcon_switch_nb); >>>>>>>> + } else >>>>>>>> +#endif >>>>>>>> + dummycon_register_output_notifier(&fbcon_output_nb); >>>>>>>> + >>>>>>>> return; >>>>>>>> } >>>>>>>> #endif >>>>>>>> @@ -3417,8 +3447,12 @@ void __exit fb_console_exit(void) >>>>>>>> { >>>>>>>> #ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER >>>>>>>> console_lock(); >>>>>>>> - if (deferred_takeover) >>>>>>>> + if (deferred_takeover) { >>>>>>>> dummycon_unregister_output_notifier(&fbcon_output_nb); >>>>>>>> +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION >>>>>>>> + dummycon_unregister_switch_notifier(&fbcon_switch_nb); >>>>>>>> +#endif >>>>>>>> + } >>>>>>>> console_unlock(); >>>>>>>> cancel_work_sync(&fbcon_deferred_takeover_work); >>>>>>>> -- >>>>>>>> 2.43.0 >>>>>>>> >>>>>>> >>>>>> >>>> >>> >
diff --git a/drivers/video/console/Kconfig b/drivers/video/console/Kconfig index bc31db6ef7..a6e371bfb4 100644 --- a/drivers/video/console/Kconfig +++ b/drivers/video/console/Kconfig @@ -138,6 +138,19 @@ config FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER by the firmware in place, rather then replacing the contents with a black screen as soon as fbcon loads. +config FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION + string "Framebuffer Console Deferred Takeover Condition" + depends on FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER + default "splash" + help + If enabled this defers further the framebuffer console taking over + until the first console switch has occurred. And even then only if + text has been output, and only if the specified parameter is found + on the command line. This ensures fbcon does not interrupt userspace + splash screens such as Plymouth which may be yet to start rendering + at the time of the first console output. "splash" is the simplest + distro-agnostic condition for this that Plymouth checks for. + config STI_CONSOLE bool "STI text console" depends on PARISC && HAS_IOMEM diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c index 63af6ab034..98155d2256 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -76,6 +76,7 @@ #include <linux/crc32.h> /* For counting font checksums */ #include <linux/uaccess.h> #include <asm/irq.h> +#include <asm/cmdline.h> #include "fbcon.h" #include "fb_internal.h" @@ -3358,6 +3359,26 @@ static int fbcon_output_notifier(struct notifier_block *nb, return NOTIFY_OK; } + +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION +static int initial_console; +static struct notifier_block fbcon_switch_nb; + +static int fbcon_switch_notifier(struct notifier_block *nb, + unsigned long action, void *data) +{ + struct vc_data *vc = data; + + WARN_CONSOLE_UNLOCKED(); + + if (vc->vc_num != initial_console) { + dummycon_unregister_switch_notifier(&fbcon_switch_nb); + dummycon_register_output_notifier(&fbcon_output_nb); + } + + return NOTIFY_OK; +} +#endif #endif static void fbcon_start(void) @@ -3370,7 +3391,16 @@ static void fbcon_start(void) if (deferred_takeover) { fbcon_output_nb.notifier_call = fbcon_output_notifier; - dummycon_register_output_notifier(&fbcon_output_nb); +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION + if (cmdline_find_option_bool(boot_command_line, + CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION)) { + initial_console = fg_console; + fbcon_switch_nb.notifier_call = fbcon_switch_notifier; + dummycon_register_switch_notifier(&fbcon_switch_nb); + } else +#endif + dummycon_register_output_notifier(&fbcon_output_nb); + return; } #endif @@ -3417,8 +3447,12 @@ void __exit fb_console_exit(void) { #ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER console_lock(); - if (deferred_takeover) + if (deferred_takeover) { dummycon_unregister_output_notifier(&fbcon_output_nb); +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER_CONDITION + dummycon_unregister_switch_notifier(&fbcon_switch_nb); +#endif + } console_unlock(); cancel_work_sync(&fbcon_deferred_takeover_work);
Until now, deferred console takeover only meant defer until there is output. But that risks stepping on the toes of userspace splash screens, as console messages may appear before the splash screen. So check the command line for the expectation of userspace splash and if present then extend the deferral until after the first switch. V2: Added Kconfig option instead of hard coding "splash". Closes: https://bugs.launchpad.net/bugs/1970069 Cc: Mario Limonciello <mario.limonciello@amd.com> Signed-off-by: Daniel van Vugt <daniel.van.vugt@canonical.com> --- drivers/video/console/Kconfig | 13 +++++++++++ drivers/video/fbdev/core/fbcon.c | 38 ++++++++++++++++++++++++++++++-- 2 files changed, 49 insertions(+), 2 deletions(-)