http://bugzilla.kernel.org/show_bug.cgi?id=9444
Summary: AE_NO_ACPI_TABLES - Acer Travelmate C104TCi
Product: ACPI
Version: 2.5
KernelVersion: 2.6.23
Platform: All
OS/Version: Linux
Tree: Mainline
Status: NEW
Severity: normal
Priority: P1
Component: Config-Tables
AssignedTo: [EMAIL PROTECTED]
ReportedBy: [EMAIL PROTECTED]
CC: [email protected]
From: TJ
I've been debugging an ACPI-disabled-at-boot failure on an Acer
Travelmate C104TCi (C100) with a Wistron BIOS.
[ 0.000000] DMI 2.3 present.
[ 0.000000] ACPI: RSDP 000EC2D0, 0014 (r0 Acer )
[ 0.000000] ACPI: 00000000, F000FF5A (r195 Zÿ F000FF57 Zÿ F000FEA5)
[ 27.751333] ACPI: Core revision 20070126
[ 27.751501] ACPI Exception (tbxface-0618): AE_NO_ACPI_TABLES, While
loading namespace from ACPI tables [20070126]
[ 27.751654] ACPI: Unable to load the System Description Tables
[ 27.783596] ACPI: Interpreter disabled.
There are several references to this problem around the net and a couple
of invasive kernel patches that don't address the cause.
I wrote a user-space application that scans memory using the method
described in the ACPI specifications. It reports:
$ sudo ./find-RSDP
find-RSDP version 0.1 © 2007 TJ
Licensed on the terms of GPL version 3
Finds ACPI Root System Descriptor Pointer (for supported BIOS's only).
0x00000000FFFFFFFF Memory size
0x00000000000EC2D0 "RSD PTR "
0x00000000000FE030 "RSD PTR " RSDT @ 0FFE0000 OEM: "Acer " sum: 0
0x0000000005FBFE10 "RSD PTR "
Unfortunately the kernel function
arch/i386/kernel/acpi/boot.c::acpi_scan_rsdp()
doesn't fully implement the ACPI specification - it simply looks for the
first "RSD PTR " signature but doesn't check it has found a valid table
by calculating the checksum.
Because this series of BIOSs happen to have multiple instances of "RSD
PTR " and an invalid instance appears first in memory, the kernel tries
to use an invalid pointer to the RSDT, leading to the problems.
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