Re: [PATCH V3 1/3] vfio, platform: add support for ACPI while detecting the reset driver

[okaya]

On 2016-03-29 05:25, Arnd Bergmann wrote:
> On Monday 28 March 2016 09:35:22 Sinan Kaya wrote:
> > The code is using the compatible DT string to associate a reset driver 
> > with
> > the actual device itself. The compatible string does not exist on ACPI
> > based systems. HID is the unique identifier for a device driver 
> > instead.
> > The change allows a driver to register with DT compatible string or 
> > ACPI
> > HID and then match the object with one of these conditions.
> >
> > Rules for loading the reset driver are as follow:
> > - ACPI HID needs match for ACPI systems
> > - DT compat needs to match for OF systems
> >
> > Tested-by: Eric Auger <eric.auger@xxxxxxxxxx> (device tree only)
> > Tested-by: Shanker Donthineni <shankerd@xxxxxxxxxxxxxx> (ACPI only)
> > Signed-off-by: Sinan Kaya <okaya@xxxxxxxxxxxxxx>
>
>
> This really feels wrong for two reasons:
>
> * device assignment of non-PCI devices is really special and doesn't
>   seem to make sense on general purpose servers that would be the 
> target
>   for ACPI normally


Why is it special? Acpi is not equal to pci. Platform devices are first 
class devices too. Especially, _cls was introduced for this reason.


> * If there is indeed a requirement for ACPI to handle something like 
> this,
>   it should be part of the ACPI spec, with a well-defined method of 
> handling
>   reset, rather than having to add a device specific hack for each
>   device separately.

I see. Normally, this is done by calling _rst method. AFAIK, Linux 
doesnât support _rst. I can check its presence and call it if it is 
there.



> 	Arnd