Re: [PATCH] ACPI driver support for pata

[Alan <alan@lxorguk.ukuu.org.uk>]

> Couldn't be do this generically inside libata core somehow, i.e. try to 
> use ACPI to set the proper mode and fall back to the driver-specific 
> mode setting code if that didn't work? I think if we could do that it 

We want to use the native hebaviour first

> would solve a number of problems (i.e. we could prevent it from doing 
> this on SATA controllers which appear to be IDE based on the PCI ID, 
> like the NVIDIA SATA controllers, since the _GTM and _STM methods seem 
> to have undefined behavior on SATA). This would also eliminate the need 

We check this already. A PATA interface without GTM/STM and friends will
not be picked up by pata_acpi but passed on to ata_generic.

> for mkinitrd, people, etc. to know that they're supposed to be loading 
> this other pata_acpi driver instead, since any PATA driver could take 
> advantage of this feature.

The link order is set up so that we try things in a very specific
deliberate order

- Hardware specific driver (unless it deliberately punts to ACPI)
- ACPI driver using _GTM/_STM etc
- Generic PCI driver ("stay in the mode the BIOS set and pray")
- ISA register compatibility mode (PIO)

This is essentially the strategy used by the old IDE layer since way back
when (minus ACPI support) and has served us pretty well.

Alan
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