Hi
On Wed, Jun 26, 2013 at 10:49 PM, Stephen Warren swarren@wwwdotorg.org wrote:
On 06/24/2013 04:27 PM, David Herrmann wrote:
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" device 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.
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.
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
+config X86_SYSFB
bool "Mark VGA/VBE/EFI FB as generic system framebuffer"helpFirmwares often provide initial graphics framebuffers so the BIOS,bootloader or kernel can show basic video-output during boot foruser-guidance and debugging. Historically, x86 used the VESA BIOSExtensions and EFI-framebuffers for this, which are mostly limitedto x86. However, a generic system-framebuffer initialization emergedrecently on some non-x86 architectures.After this patch has been in the kernel a while, that very last won't really be true; simplefb won't have been introduced recently. Perhaps just delete that one sentence?
It rather belongs in the commit message, right. I will rephrase that.
This option, if enabled, marks VGA/VBE/EFI framebuffers as genericframebuffers so the new generic system-framebuffer drivers can beused on x86.This breaks any x86-only driver like efifb, vesafb, uvesafb, whichwill not work if this is selected.Doesn't that imply that some form of conflicts or depends ! statement should be added here?
There is no real conflict here. You still can use vesafb/... with this option, but they will not pick up the device. I intend to fix these up to use "platform-framebuffer" devices instead of globally binding to "struct screen_info". This way, framebuffers either end up as simple-framebuffers or platform-framebuffers. This option selects which device they end up as.
As all non-compatible framebuffers (with incompatible pixel-formats) always end up as "platform-framebuffer", it still makes sense to use vesafb as fallback. Hence, I'd not introduce any "conflicts" dependency here. Maybe I should rephrase the warning to something that makes clear that if this option is selected, you need simplefb.c or simpledrm to make use of these devices.
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
+obj-y += sysfb.o
I suspect that should be obj-$(CONFIG_X86_SYSFB) += sysfb.o.
No. This patch tries to solve two things: First of all, every system-framebuffer now gets a "platform-framebuffer" platform-device. Iff X86_SYSFB is selected, it additionally tries to parse the framebuffer information as "simple-framebuffer". If it succeeds, it created a "simple-framebuffer" object, if it doesn't, a fallback "platform-framebuffer" is provided.
This series is missing vesafb/efifb/.. patches, which should now bind to "platform-framebuffer" devices instead of using "struct screen_info" directly. I intend to add these in the next round.
diff --git a/arch/x86/kernel/sysfb.c b/arch/x86/kernel/sysfb.c
+#ifdef CONFIG_X86_SYSFB
Rather than ifdef'ing the body of this file, why not create a dummy static inline version of add_sysfb() and put that into a header file that users include. There should be a header file to prototype the function anyway. That way, you avoid all of the ifdefs and static inline functions in this file.
+static bool parse_mode(const struct screen_info *si,
struct simplefb_platform_data *mode)
strlcpy(mode->format, f->name, sizeof(mode->format));Per my comments about the type of mode->format, I think that could just be:
mode->format = f->name;
... since formats[] (i.e. f) isn't initdata.
+#else /* CONFIG_X86_SYSFB */
+static bool parse_mode(const struct screen_info *si,
struct simplefb_platform_data *mode)+{
return false;+}
+static int create_simplefb(const struct screen_info *si,
const struct simplefb_platform_data *mode)+{
return -EINVAL;+}
+#endif /* CONFIG_X86_SYSFB */
Following on from my ifdef comment above, I believe those versions of those functions will always cause add_sysfb() to return -ENODEV, so you may as well provide a static inline for add_sysfb() instead.
No. add_sysfb() is supposed to always succeed. However, if parse_mode/create_simplefb fail, it creates a "platform-framebuffer" as fallback. I don't see any way to avoid these ifdefs. Considering the explanation above, could you elaborate how you think this should work?
Thanks David