Messages in this thread | | | Subject | Re: [PATCH v3 3/3] console/fbcon: Add support for deferred console takeover | From | Hans de Goede <> | Date | Thu, 28 Jun 2018 10:58:42 +0200 |
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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 > > >
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