linux-kernel - Re: [PATCH V8 4/9] vfio: platform: add support for ACPI probe

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Message-ID: <20f7d42e-8d15-49ad-6c6a-eda489546f20@codeaurora.org>
Date:	Wed, 13 Jul 2016 17:01:32 -0400
From:	Sinan Kaya <okaya@...eaurora.org>
To:	Alex Williamson <alex.williamson@...hat.com>
Cc:	kvm@...r.kernel.org, timur@...eaurora.org, cov@...eaurora.org,
	jcm@...hat.com, eric.auger@...hat.com, linux-acpi@...r.kernel.org,
	agross@...eaurora.org, linux-arm-msm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Baptiste Reynal <b.reynal@...tualopensystems.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V8 4/9] vfio: platform: add support for ACPI probe

On 7/13/2016 4:09 PM, Alex Williamson wrote:
>> et me explain the rationale.
>> > 
>> > As you know, there can be two kernel build combinations. One build where 
>> > ACPI is not selected in Kconfig and another one with the ACPI Kconfig.
>> > 
>> > In the first case, CONFIG_ACPI is stubbed out in this file and DT user
>> > will not see any kind of messages from ACPI. 
>> > 
>> > In the second case, both DT and ACPI is compiled in but the system is booting with
>> > any of these combinations. 
>> > 
>> > If the firmware is DT type, then acpi_disabled is 1. The ACPI probe routine
>> > terminates immediately without any messages. 
>> > 
>> > If the firmware is ACPI type, then acpi_disabled is 0. All other checks are valid
>> > checks. We cannot claim that this system is DT.
> 
> Thanks, this sort of information and assumption should be documented in
> a comment since not all of us care whether a DT device can appear in an
> ACPI config or not.  Also note that acpi_disabled and ACPI_COMPANION
> are defined regardless of CONFIG_ACPI, so really we only need to wrap
> acpi_device_hid() in an #ifdef, we could skip the separate stub.
> Thanks,

Sure, I'll add the sentences above as a comment to top of the probe function.

I also got rid of stub vfio_platform_acpi_probe function and moved CONFIG_ACPI
inside the vfio_platform_acpi_probe function as you suggested.

-- 
Sinan Kaya
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.