From 64b3db22c04586997ab4be46dd5a5b99f8a2d390 Mon Sep 17 00:00:00 2001 From: Bob Moore Date: Mon, 14 Feb 2011 15:50:42 +0800 Subject: ACPICA: Remove use of unreliable FADT revision field The revision number in the FADT has been found to be completely unreliable and cannot be trusted. Only the table length can be used to infer the actual version. Signed-off-by: Bob Moore Signed-off-by: Lin Ming Signed-off-by: Len Brown --- drivers/acpi/acpica/tbfadt.c | 5 ++++- include/acpi/actbl.h | 16 ++++++++++++++++ 2 files changed, 20 insertions(+), 1 deletion(-) diff --git a/drivers/acpi/acpica/tbfadt.c b/drivers/acpi/acpica/tbfadt.c index 428d44e2d162..6f5588e62c0a 100644 --- a/drivers/acpi/acpica/tbfadt.c +++ b/drivers/acpi/acpica/tbfadt.c @@ -384,8 +384,11 @@ static void acpi_tb_convert_fadt(void) * * The ACPI 1.0 reserved fields that will be zeroed are the bytes located at * offset 45, 55, 95, and the word located at offset 109, 110. + * + * Note: The FADT revision value is unreliable. Only the length can be + * trusted. */ - if (acpi_gbl_FADT.header.revision < FADT2_REVISION_ID) { + if (acpi_gbl_FADT.header.length <= ACPI_FADT_V2_SIZE) { acpi_gbl_FADT.preferred_profile = 0; acpi_gbl_FADT.pstate_control = 0; acpi_gbl_FADT.cst_control = 0; diff --git a/include/acpi/actbl.h b/include/acpi/actbl.h index 7e42bfee0e29..d41c94885211 100644 --- a/include/acpi/actbl.h +++ b/include/acpi/actbl.h @@ -343,4 +343,20 @@ struct acpi_table_desc { #include #include +/* + * Sizes of the various flavors of FADT. We need to look closely + * at the FADT length because the version number essentially tells + * us nothing because of many BIOS bugs where the version does not + * match the expected length. In other words, the length of the + * FADT is the bottom line as to what the version really is. + * + * For reference, the values below are as follows: + * FADT V1 size: 0x74 + * FADT V2 size: 0x84 + * FADT V3+ size: 0xF4 + */ +#define ACPI_FADT_V1_SIZE (u32) (ACPI_FADT_OFFSET (flags) + 4) +#define ACPI_FADT_V2_SIZE (u32) (ACPI_FADT_OFFSET (reserved4[0]) + 3) +#define ACPI_FADT_V3_SIZE (u32) (sizeof (struct acpi_table_fadt)) + #endif /* __ACTBL_H__ */ -- cgit v1.2.3