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

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Date:	Tue, 29 Mar 2016 11:25:47 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	linux-arm-kernel@...ts.infradead.org
Cc:	Sinan Kaya <okaya@...eaurora.org>, kvm@...r.kernel.org,
	timur@...eaurora.org, cov@...eaurora.org, jcm@...hat.com,
	eric.auger@...aro.org, mark.rutland@....com,
	devicetree@...r.kernel.org,
	Baptiste Reynal <b.reynal@...tualopensystems.com>,
	vikrams@...eaurora.org, marc.zyngier@....com,
	linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
	vinod.koul@...el.com, Alex Williamson <alex.williamson@...hat.com>,
	agross@...eaurora.org, Dan Carpenter <dan.carpenter@...cle.com>,
	shankerd@...eaurora.org
Subject: Re: [PATCH V3 1/3] vfio, platform: add support for ACPI while detecting the reset driver

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@...aro.org> (device tree only)
> Tested-by: Shanker Donthineni <shankerd@...eaurora.org> (ACPI only)
> Signed-off-by: Sinan Kaya <okaya@...eaurora.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

* 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.

	Arnd