On Tuesday 13 November 2007 03:59:36 pm Kristen Carlson Accardi wrote: > On Tue, 13 Nov 2007 12:26:32 -0800 Greg KH <greg@xxxxxxxxx> wrote: > > And isn't there some other tool that dumps the raw ACPI tables? I > > thought the acpi developers used it all the time when debugging things > > with users. > > There are - people should take a look at the Intel Linux Firmware Kit > for an example of how to parse ACPI tables in userspace - the code > is also GPL'd, so you are free to use it in another GPL application. > > http://www.linuxfirmwarekit.org/download.php#source > > In many DSDTs I've seen, _SUN is hardcoded anyway and can be found > by reading the DSDT from userspace. This is what the firmwarekit > does to check for duplicate _SUN in one of it's tests. I see three relevant things in the firmware kit: 1) ExecuteAmlMethod() in amlpoke/amlpoke.c. This uses /proc/acpi/hotkey/event_config to cause the kernel to execute an AML method. This looks similar to what dev_acpi does and is unsafe for the same reasons (the method may have side effects that interfere with kernel drivers). The kernel support for this was removed in 2.6.21: http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=5ee6edbcde4d3b14e4e03d4b331df1099a34aa8d 2) execute_aml_method() in acpitable.c. Similar to above. 3) parse_SUN_name() in SUN/SUN.c. This uses acpidump, acpixtract, and iasl -d to disassemble the DSDT and SSDTs, then looks for things like "Name (_SUN, 0x0000012C)". That works well if _SUN merely returns a constant, and many DSDTs do that. But _SUN can be implemented as a control method, and then we have a problem because we can't determine the _SUN value by inspecting the DSDT. We have to evaluate the method, and that may require operation regions, semaphores, etc., so it can only be done in the kernel. So I agree that the firmware kit has a clever hack that works on much existing x86 firmware, and it sounds like Tivoli might even rely on it. But I don't feel good about it, and it could easily break when some BIOS writer needs to make _SUN slightly more complicated. Bjorn - To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
