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    SubjectRe: [PATCH] x86/efi-bgrt: remove the check of the version field
    On 08/15/16 at 01:56pm, Matt Fleming wrote:
    > On Tue, 09 Aug, at 01:25:46PM, Icenowy Zheng wrote:
    > > Some broken firmwares have a wrongly filled version field in BGRT table.
    > > (See http://wiki.osdev.org/Broken_UEFI_implementations )
    > >
    > > As we know, these firmwares can also provide correct BGRT image, although
    > > the table is wrong.
    > >
    > > After removing the check of the version field, the kernel can now extract
    > > the image correctly, and the information is also correct.
    > >
    > > Tested on a Thinkpad E531 (68854UC).
    > >
    > > Signed-off-by: Icenowy Zheng <icenowy@aosc.xyz>
    > > ---
    > > arch/x86/platform/efi/efi-bgrt.c | 5 -----
    > > 1 file changed, 5 deletions(-)
    > >
    > > diff --git a/arch/x86/platform/efi/efi-bgrt.c b/arch/x86/platform/efi/efi-bgrt.c
    > > index 6a2f569..f492ea0 100644
    > > --- a/arch/x86/platform/efi/efi-bgrt.c
    > > +++ b/arch/x86/platform/efi/efi-bgrt.c
    > > @@ -47,11 +47,6 @@ void __init efi_bgrt_init(void)
    > > bgrt_tab->header.length, sizeof(*bgrt_tab));
    > > return;
    > > }
    > > - if (bgrt_tab->version != 1) {
    > > - pr_notice("Ignoring BGRT: invalid version %u (expected 1)\n",
    > > - bgrt_tab->version);
    > > - return;
    > > - }
    > > if (bgrt_tab->status & 0xfe) {
    > > pr_notice("Ignoring BGRT: reserved status bits are non-zero %u\n",
    > > bgrt_tab->status);
    >
    > This would be less scary if we checked for known broken and known good
    > version values instead of removing the check altogether, i.e. 0 and 1.

    Could we add some quirk for these broken hardware instead of changing
    the normal code?

    >
    > The whole point of the version field is that it tells us about the
    > layout of the BGRT table, so it's not exactly a useless check.

    Agreed.

    Thanks
    Dave

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