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| author | Hans de Goede <hdegoede@redhat.com> | 2018-06-28 15:20:30 +0200 |
|---|---|---|
| committer | Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com> | 2018-06-28 15:20:30 +0200 |
| commit | 83d83bebf40132e2d55ec58af666713cc76f9764 (patch) | |
| tree | 8539ca6adfd8778e9c73111e23770adc7b04beb2 /Documentation/fb | |
| parent | 3bd3a0e330aae4fffa8028aba2407ef615ab040b (diff) | |
| download | lwn-83d83bebf40132e2d55ec58af666713cc76f9764.tar.gz lwn-83d83bebf40132e2d55ec58af666713cc76f9764.zip | |
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 <daniel.vetter@ffwll.ch>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Diffstat (limited to 'Documentation/fb')
| -rw-r--r-- | Documentation/fb/fbcon.txt | 7 |
1 files changed, 7 insertions, 0 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 |