On Sun, 26 Jan 2020 at 16:02, Hans de Goede <hdegoede@xxxxxxxxxx> 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@xxxxxxxxxxxxxxx > BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=1791273 > Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx> > --- > 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 ...