x86: provide platform-devices for boot-framebuffers
The current situation regarding boot-framebuffers (VGA, VESA/VBE, EFI) on
x86 causes troubles when loading multiple fbdev drivers. The global
"struct screen_info" does not provide any state-tracking about which
drivers use the FBs. request_mem_region() theoretically works, but
unfortunately vesafb/efifb ignore it due to quirks for broken boards.
Avoid this by creating a platform framebuffer devices with a pointer
to the "struct screen_info" as platform-data. Drivers can now create
platform-drivers and the driver-core will refuse multiple drivers being
active simultaneously.
We keep the screen_info available for backwards-compatibility. Drivers
can be converted in follow-up patches.
Different devices are created for VGA/VESA/EFI FBs to allow multiple
drivers to be loaded on distro kernels. We create:
- "vesa-framebuffer" for VBE/VESA graphics FBs
- "efi-framebuffer" for EFI FBs
- "platform-framebuffer" for everything else
This allows to load vesafb, efifb and others simultaneously and each
picks up only the supported FB types.
Apart from platform-framebuffer devices, this also introduces a
compatibility option for "simple-framebuffer" drivers which recently got
introduced for OF based systems. If CONFIG_X86_SYSFB is selected, we
try to match the screen_info against a simple-framebuffer supported
format. If we succeed, we create a "simple-framebuffer" device instead
of a platform-framebuffer.
This allows to reuse the simplefb.c driver across architectures and also
to introduce a SimpleDRM driver. There is no need to have vesafb.c,
efifb.c, simplefb.c and more just to have architecture specific quirks
in their setup-routines.
Instead, we now move the architecture specific quirks into x86-setup and
provide a generic simple-framebuffer. For backwards-compatibility (if
strange formats are used), we still allow vesafb/efifb to be loaded
simultaneously and pick up all remaining devices.
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Link: http://lkml.kernel.org/r/1375445127-15480-4-git-send-email-dh.herrmann@gmail.com
Tested-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index b32ebf9..5c56559 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2270,6 +2270,32 @@
source "drivers/rapidio/Kconfig"
+config X86_SYSFB
+ bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
+ help
+ Firmwares often provide initial graphics framebuffers so the BIOS,
+ bootloader or kernel can show basic video-output during boot for
+ user-guidance and debugging. Historically, x86 used the VESA BIOS
+ Extensions and EFI-framebuffers for this, which are mostly limited
+ to x86.
+ This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
+ framebuffers so the new generic system-framebuffer drivers can be
+ used on x86. If the framebuffer is not compatible with the generic
+ modes, it is adverticed as fallback platform framebuffer so legacy
+ drivers like efifb, vesafb and uvesafb can pick it up.
+ If this option is not selected, all system framebuffers are always
+ marked as fallback platform framebuffers as usual.
+
+ Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
+ not be able to pick up generic system framebuffers if this option
+ is selected. You are highly encouraged to enable simplefb as
+ replacement if you select this option. simplefb can correctly deal
+ with generic system framebuffers. But you should still keep vesafb
+ and others enabled as fallback if a system framebuffer is
+ incompatible with simplefb.
+
+ If unsure, say Y.
+
endmenu