linux-kernel - Re: [RFC PATCH v2 01/16] ACPI: Add support for device specific properties

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Message-ID: <D058106C.ABC8C%dvhart@linux.intel.com>
Date:	Mon, 06 Oct 2014 09:25:35 -0700
From:	Darren Hart <dvhart@...radead.org>
To:	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Grant Likely <grant.likely@...aro.org>
CC:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	<linux-acpi@...r.kernel.org>, <devicetree@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Alexandre Courbot <gnurou@...il.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Bryan Wu <cooloney@...il.com>,
	Lee Jones <lee.jones@...aro.org>,
	Arnd Bergmann <arnd@...db.de>, Aaron Lu <aaron.lu@...el.com>
Subject: Re: [RFC PATCH v2 01/16] ACPI: Add support for device specific
 properties

On 10/6/14, 7:32, "Mika Westerberg" <mika.westerberg@...ux.intel.com>
wrote:

>On Mon, Oct 06, 2014 at 02:50:21PM +0100, Grant Likely wrote:
>>
>> > +/* ACPI _DSD device properties UUID:
>>daffd814-6eba-4d8c-8a91-bc9bbf4aa301 */
>> > +static const u8 prp_uuid[16] = {
>> > +	0x14, 0xd8, 0xff, 0xda, 0xba, 0x6e, 0x8c, 0x4d,
>> > +	0x8a, 0x91, 0xbc, 0x9b, 0xbf, 0x4a, 0xa3, 0x01
>> > +};
>> 
>> ?
>> 
>> What is the encoding used here? I see the first 4 bytes for "daffd814"
>> encoded in little endian (0x14 first), and then the remaining values
>> encoded in big-endian for each number. Is this typical for UUID values?
>
>The buffer format is explained in ACPI 5.1 spec, page 823.
>
>I generated the above so that I compiled a _DSD with correct UUID using
>iASL and then disassambled it with the same tool.
>

I bugged Mika with the same question, it's a fairly non-intuitive encoding
:-)

-- 
Darren Hart
Intel Open Source Technology Center



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