Re: [Linaro-acpi] [PATCH v5 18/18] Documentation: ACPI for ARM64

From: Jon Masters <jcm@redhat.com>
To: Arnd Bergmann <arnd@arndb.de>, linaro-acpi@lists.linaro.org
Cc: Catalin Marinas <catalin.marinas@arm.com>,
	Liviu Dudau <Liviu.Dudau@arm.com>, Lv Zheng <lv.zheng@intel.com>,
	Rob Herring <robh@kernel.org>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	Robert Moore <robert.moore@intel.com>,
	"linux-acpi@vger.kernel.org" <linux-acpi@vger.kernel.org>,
	Robert Richter <rric@kernel.org>,
	Jason Cooper <jason@lakedaemon.net>,
	Marc Zyngier <Marc.Zyngier@arm.com>,
	Will Deacon <Will.Deacon@arm.com>,
	Mark Brown <broonie@kernel.org>,
	Bjorn Helgaas <bhelgaas@google.com>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	Randy Dunlap <rdunlap@infradead.org>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Olof Johansson <olof@lixom.net>
Subject: Re: [Linaro-acpi] [PATCH v5 18/18] Documentation: ACPI for ARM64
Date: Tue, 06 Jan 2015 23:55:58 -0500	[thread overview]
Message-ID: <54ACBC5E.3040905@redhat.com> (raw)
In-Reply-To: <54AC5C57.7050504@redhat.com>

On 01/06/2015 05:06 PM, Jon Masters wrote:
> Hi Arnd,
> 
> Happy New Year!
> 
> On 01/06/2015 02:21 PM, Arnd Bergmann wrote:
>> On Tuesday 06 January 2015 11:24:43 Jon Masters wrote:
>>> On 01/06/2015 06:20 AM, Catalin Marinas wrote:
>>>
>>>> Now, what's preventing a vendor firmware from providing only ACPI
>>>> tables? Do we enforce it in some way (arm-acpi.txt, kernel warning etc.)
>>>> that both DT and ACPI are supported, or at least that dts files are
>>>> merged in the kernel first?
>>>
>>> I know of some (server) firmware that will only provide ACPI in the
>>> medium term, so this is coming.
>>
>> Medium term is fine, as long as they are not expecting their hardware
>> to be supported by Linux before ACPI support is stable enough for
>> general consumption.
> 
> To be clear, I think that's reasonable for upstream. I may love ACPI,
> but vendors can always ship kernels with a config supporting ACPI only
> platforms in the interim period if they have a commercial justification
> and that doesn't have to be supported in terms of the upstream default.
> 
> But, perhaps there's a way to have it both ways, you could consider also
> a CONFIG_EXPERT option that would allow you to build a kernel with ACPI
> only support in the medium term. That way, if someone is running a
> vendor kernel, but wants to track upstream development more closely,
> they can do so on such hardware by enabling the expert config bit.

Clarification: I'm suggesting that in the medium term the dependency
upon CONFIG_EXPERT either goes away or is replaced with requiring ACPI
and DTB in the non "expert" case and requiring "expert" selected to
allow a kernel that will boot with ACPI only. But only a suggestion.

Jon.