Re: [PATCH 07/13] libata-acpi: add ATA_FLAG_ACPI_SATA port flag

[Tejun Heo <htejun@gmail.com>]

Alan Cox wrote:
> On Mon, 23 Apr 2007 02:41:06 +0900
> Tejun Heo <htejun@gmail.com> wrote:
> 
>> Whether a controller needs IDE or SATA ACPI hierarchy is determined by
>> the programming interface of the controller not by whether the
>> controller is SATA or PATA
> 
> NAK
> 
> I keep trying to point out that this is not true.
> 
> The ACPI interface to use can only be safely determined one way - and
> that is to see what methods the BIOS has attached to the device and use
> those.
> 
> Take the ACPI handle, go look for _GTF, _SDD etc and believe the
> firmware. Nothing else works.

Actually, that's dangerous.  For example, you must not do _STM/_GTM on
ahci becuase _STM/_GTM access PCI config registers which must not be
accessed in achi modes and some BIOSen supply the same _STM/_GTM nodes
whether the controller is in ata_piix mode or ahci mode.  Also, on ICH8,
the association gets quite weird due to PCI device splitting.

The ACPI spec says the layout is dependent on controller interface and I
 can see reasons why we need to follow that but not the other way
around.  Do you have counter-examples?

-- 
tejun