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

[Muhammad Bilal <meatuni001@gmail.com>]

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.

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(-)

-- 
2.54.0