Re: [PATCH 0/2] platform/x86: hp-bioscfg: fix attribute enumeration on older HP BIOS

[Armin Wolf]

Am 26.06.26 um 22:49 schrieb Muhammad Bilal:

> The hp_bioscfg driver silently fails to enumerate BIOS attributes on
> HP EliteBook 840 G2 (and potentially other older HP models) because:
>
>    1. hp_init_bios_package_attribute() hard-fails when a WMI ACPI package
>       contains fewer elements than the per-type expected count (11 < 13),
>       even though only the first 10 common elements are required to
>       register an attribute.
>
>    2. hp_populate_enumeration_elements_from_package() returns -EIO and
>       discards the entire attribute when any single element has an
>       unexpected ACPI object type — typically after a BIOS AML error
>       returns malformed data.

Hi,

it could be that the ACPI firmware still transmits all the necessary data, its just
that some package elements are combined into a single buffer element
(see https://docs.kernel.org/wmi/acpi-interface.html section "Conversion rules for ACPI data types"
for details).

The correct solution would be to migrate the driver to the new buffer-based WMI API,
because said API ensures that ACPI objects are properly marshaled into the common
WMI data format. However this might require a lot of work :/.

Regarding the BIOS error: this usually happens because creating a ByteField with and
invalid length does not cause an error under Windows. Passing a larger buffer usually
fixes this problem.

Thanks,
Armin Wolf

> Hardware affected:
>    HP EliteBook 840 G2 (DMI: Hewlett-Packard HP EliteBook 840 G2/2216)
>    BIOS: M71 Ver. 01.31 (02/24/2020)
>
> How to reproduce:
>    1. Boot a kernel with CONFIG_HP_BIOSCFG=m on an HP EliteBook 840 G2
>    2. modprobe hp_bioscfg
>    3. Observe dmesg:
>         hp_bioscfg: ACPI-package does not have enough elements: 11 < 13
>         Error expected type 2 for elem 13, but got type 1 instead
>
> Testing notes:
>    Tested on HP EliteBook 840 G2 running Arch Linux kernel 7.0.13-arch1-1.
>    After patches, hp_bioscfg loads successfully and enumerates available
>    BIOS attributes. Attributes with shortened packages are partially
>    populated and accessible via sysfs. No regressions on systems that
>    return full 13-element packages (checked via code inspection —
>    pr_warn path is only reached when count < min_elements).
>
> Relevant dmesg (before fix):
>    [   11.xxx] hp_bioscfg: ACPI-package does not have enough elements:
>                11 < 13
>    [   11.xxx] ACPI BIOS Error (bug): AE_AML_BUFFER_LIMIT,
>                Index (0x000000032) is beyond end of object (length 0x32)
>    [   11.xxx] ACPI Error: Aborting method \_SB.WMID.WQBE
>    [   11.xxx] Error expected type 2 for elem 13, got type 1
>    [   11.xxx] hp_bioscfg: Returned error 0x3
>
> Muhammad Bilal (2):
>    platform/x86: hp-bioscfg: accept reduced ACPI packages from older HP
>      BIOS
>    platform/x86: hp-bioscfg: warn on element type mismatch instead of
>      failing
>
>   drivers/platform/x86/hp/hp-bioscfg/bioscfg.c         | 11 ++++++++---
>   drivers/platform/x86/hp/hp-bioscfg/bioscfg.h         |  3 +++
>   drivers/platform/x86/hp/hp-bioscfg/enum-attributes.c |  7 ++++---
>   3 files changed, 15 insertions(+), 6 deletions(-)