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"
> + 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. However, a generic system-framebuffer initialization emerged
> + recently 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?
> + This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
> + framebuffers so the new generic system-framebuffer drivers can be
> + used on x86.
> +
> + This breaks any x86-only driver like efifb, vesafb, uvesafb, which
> + will not work if this is selected.
Doesn't that imply that some form of conflicts or depends ! statement
should be added here?
> 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.
> 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.
