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Re: [PATCH v4 3/8] x86/EFI: retrieve EDID


  • To: Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Wed, 6 Apr 2022 16:24:52 +0200
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  • Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Wed, 06 Apr 2022 14:25:09 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 31.03.2022 11:45, Jan Beulich wrote:
> When booting directly from EFI, obtaining this information from EFI is
> the only possible way. And even when booting with a boot loader
> interposed, it's more clean not to use legacy BIOS calls for this
> purpose. (The downside being that there are no "capabilities" that we
> can retrieve the EFI way.)
> 
> To achieve this we need to propagate the handle used to obtain the
> EFI_GRAPHICS_OUTPUT_PROTOCOL instance for further obtaining an
> EFI_EDID_*_PROTOCOL instance, which has been part of the spec since 2.5.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> ---
> Setting boot_edid_caps to zero isn't desirable, but arbitrarily setting
> one or both of the two low bits also doesn't seem appropriate.
> 
> GrUB also checks an "agp-internal-edid" variable. As I haven't been able
> to find any related documentation, and as GrUB being happy about the
> variable being any size (rather than at least / precisely 128 bytes),
> I didn't follow that route.
> ---
> v3: Re-base.
> v2: New.
> 
> --- a/xen/arch/arm/efi/efi-boot.h
> +++ b/xen/arch/arm/efi/efi-boot.h
> @@ -464,6 +464,10 @@ static void __init efi_arch_edd(void)
>  {
>  }
>  
> +static void __init efi_arch_edid(EFI_HANDLE gop_handle)
> +{
> +}
> +
>  static void __init efi_arch_memory_setup(void)
>  {
>  }

May I ask for an Arm side ack here, please?

Thanks, Jan




 


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