linux-kernel - Re: [PATCH v2 8/9] efi/arm*: wire up struct screen

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Date:	Mon, 21 Mar 2016 14:53:11 +0100
From:	David Herrmann <dh.herrmann@...il.com>
To:	Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-efi@...r.kernel.org,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Matt Fleming <matt@...eblueprint.co.uk>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Peter Jones <pjones@...hat.com>, leif.lindholm@...aro.org,
	Mark Rutland <mark.rutland@....com>,
	"the arch/x86 maintainers" <x86@...nel.org>
Subject: Re: [PATCH v2 8/9] efi/arm*: wire up struct screen_info to
 efi-framebuffer platform device

Hi

On Fri, Mar 18, 2016 at 5:47 PM, Ard Biesheuvel
<ard.biesheuvel@...aro.org> wrote:
> This adds code to the ARM and arm64 EFI init routines to expose a platform
> device of type 'efi-framebuffer' if struct screen_info has been populated
> appropriately from the GOP protocol by the stub. Since the framebuffer may
> potentially be located in system RAM, make sure that the region is reserved
> and marked MEMBLOCK_NOMAP.
>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> ---
>  drivers/firmware/efi/arm-init.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
>
> diff --git a/drivers/firmware/efi/arm-init.c b/drivers/firmware/efi/arm-init.c
> index acd44de30504..f5f13b871d42 100644
> --- a/drivers/firmware/efi/arm-init.c
> +++ b/drivers/firmware/efi/arm-init.c
> @@ -19,6 +19,7 @@
>  #include <linux/mm_types.h>
>  #include <linux/of.h>
>  #include <linux/of_fdt.h>
> +#include <linux/platform_device.h>
>  #include <linux/screen_info.h>
>
>  #include <asm/efi.h>
> @@ -76,6 +77,10 @@ static void __init init_screen_info(void)
>                 screen_info = *si;
>                 early_memunmap(si, sizeof(*si));
>         }
> +
> +       if (screen_info.orig_video_isVGA == VIDEO_TYPE_EFI &&
> +           memblock_is_map_memory(screen_info.lfb_base))
> +               memblock_mark_nomap(screen_info.lfb_base, screen_info.lfb_size);
>  }
>
>  static int __init uefi_init(void)
> @@ -235,3 +240,16 @@ void __init efi_init(void)
>
>         init_screen_info();
>  }
> +
> +static int __init register_gop_device(void)
> +{
> +       void *pd;
> +
> +       if (screen_info.orig_video_isVGA != VIDEO_TYPE_EFI)
> +               return 0;
> +
> +       /* the efifb driver accesses screen_info directly, no need to pass it */
> +       pd = platform_device_register_simple("efi-framebuffer", 0, NULL, 0);

I'd really appreciate if you pass "screen_info" as data, just like x86
does. Sure, we still use the global screen_info variable from efifb,
but we should try to reduce the number of global variables and rather
make drivers use the platform-data of the platform device.

Thanks
David