From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
To: Hans de Goede <hdegoede@redhat.com>
Cc: Ard Biesheuvel <ardb@kernel.org>,
linux-efi <linux-efi@vger.kernel.org>,
ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
stable <stable@vger.kernel.org>
Subject: Re: [PATCH] efi/bgrt: Accept BGRT tables with a version of 0 on Lenovo laptops
Date: Tue, 28 Jan 2020 08:48:46 +0100 [thread overview]
Message-ID: <CAKv+Gu_dE+pi7CSANOXEP2xenRirWQg5H71t5f4eah8-XZpbxQ@mail.gmail.com> (raw)
In-Reply-To: <20200126150231.6021-1-hdegoede@redhat.com>
On Sun, 26 Jan 2020 at 16:02, Hans de Goede <hdegoede@redhat.com> wrote:
>
> Some (somewhat older) Lenovo laptops have a correct BGRT table, except
> that the version field is 0 instead of 1.
>
> Quickly after finding this out, even before submitting a first version of
> this patch upstream, the list of DMI matches for affected models grew to
> 3 models (all Ivy Bridge based).
>
> So rather then maintaining an ever growing list with DMI matches for
> affected Lenovo models, this commit simply checks if the vendor is Lenovo
> when the version is 0 and in that case accepts the out of spec version
> working around the Lenovo firmware bug.
>
> Cc: stable@vger.kernel.org
> BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=1791273
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> ---
> drivers/firmware/efi/efi-bgrt.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/firmware/efi/efi-bgrt.c b/drivers/firmware/efi/efi-bgrt.c
> index b07c17643210..3a2d6d3a590b 100644
> --- a/drivers/firmware/efi/efi-bgrt.c
> +++ b/drivers/firmware/efi/efi-bgrt.c
> @@ -15,6 +15,7 @@
> #include <linux/acpi.h>
> #include <linux/efi.h>
> #include <linux/efi-bgrt.h>
> +#include <linux/dmi.h>
>
> struct acpi_table_bgrt bgrt_tab;
> size_t bgrt_image_size;
> @@ -42,7 +43,12 @@ void __init efi_bgrt_init(struct acpi_table_header *table)
> return;
> }
> *bgrt = *(struct acpi_table_bgrt *)table;
> - if (bgrt->version != 1) {
> + /*
> + * Some older Lenovo laptops have a correct BGRT table, except that
> + * the version field is 0 instead of 1.
> + */
> + if (bgrt->version != 1 &&
> + !(bgrt->version == 0 && dmi_name_in_vendors("LENOVO"))) {
> pr_notice("Ignoring BGRT: invalid version %u (expected 1)\n",
> bgrt->version);
> goto out;
Hi Hans,
Given that the ACPI spec only defines a single version for this table,
which is version #1, wouldn't it be simpler to just assume that
version #0 means version #1 in all cases, rather than using DMI
matches for that? There is no risk of misidentifying another table
version, since none exist ...
next prev parent reply other threads:[~2020-01-28 7:49 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-26 15:02 [PATCH] efi/bgrt: Accept BGRT tables with a version of 0 on Lenovo laptops Hans de Goede
2020-01-28 7:48 ` Ard Biesheuvel [this message]
2020-01-31 12:47 ` Hans de Goede
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