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.au...@linaro.org> (device tree only)
Tested-by: Shanker Donthineni <shank...@codeaurora.org> (ACPI only)
Signed-off-by: Sinan Kaya <ok...@codeaurora.org>



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 
doesn’t support _rst. I can check its presence and call it if it is 
there.



        Arnd