linux-kernel - Re: [PATCH v3 02/21] libnd, nfit: initial libnd infrastructure and NFIT support

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Message-ID: <555E474B.2060306@hp.com>
Date:	Thu, 21 May 2015 16:59:55 -0400
From:	Linda Knippers <linda.knippers@...com>
To:	Toshi Kani <toshi.kani@...com>,
	Dan Williams <dan.j.williams@...el.com>
CC:	Jens Axboe <axboe@...nel.dk>,
	"linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
	Neil Brown <neilb@...e.de>,
	Greg KH <gregkh@...uxfoundation.org>,
	"Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
	"Moore, Robert" <robert.moore@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux ACPI <linux-acpi@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	"Zheng, Lv" <lv.zheng@...el.com>, Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v3 02/21] libnd, nfit: initial libnd infrastructure and
 NFIT support

On 05/21/2015 03:59 PM, Toshi Kani wrote:
> On Thu, 2015-05-21 at 13:44 -0600, Toshi Kani wrote:
>> On Thu, 2015-05-21 at 12:06 -0700, Dan Williams wrote:
>>> On Thu, May 21, 2015 at 11:01 AM, Toshi Kani <toshi.kani@...com> wrote:
>>>> On Thu, 2015-05-21 at 17:49 +0000, Moore, Robert wrote:
>>>>> What ACPICA has done here is to define these values consistently with the ToUUID ASL macro:
>>>>>
>>>>>
>>>>> Byte encoding of UUID/GUID strings into ACPI Buffer objects (use ToUUID from ASL):
>>>>>
>>>>>    Input UUID/GUID String format : aabbccdd-eeff-gghh-iijj-kkllmmnnoopp
>>>>>      Expected output ACPI buffer : dd,cc,bb,aa, ff,ee, hh,gg, ii,jj, kk,ll,mm,nn,oo,pp
>>>>>
>>>>
>>>> I do not see any issue in this conversion, which is consistent with
>>>> ToUUID defined in ACPI spec.
>>>>
>>>> My point is that the string format of GUID is endian-neutral.  Wiki
>>>> pages and EFI spec agree on it.  EFI 2.5 spec, Table 225 (sorry not
>>>> Table 212, which is v2.4), is also clear about how String and Buffer are
>>>> related with actual values of GUID.
>>>
>>> I think the critical point from the UEFI spec is the "It should also
>>> be noted that TimeLow, TimeMid, TimeHighAndVersion fields in the EFI
>>> are encoded as little endian".  That would imply the byte encoding
>>> of...
>>>
>>> { 0x92F701F6, 0x13B4, 0x405D, 0x91, 0x0B, 0x29, 0x93, 0x67, 0xE8, 0x23, 0x4C }
>>>
>>> ...should be:
>>>
>>> { f6,01,f7,92,b4,13,5d,40,91,0b,29,93,67,e8,23,4c }
>>
>> The above NFIT GUID as data values means:
>>
>> EFI_GUID(0x92F701F6, 0x13B4, 0x405D, 0x91, 0x0B, 0x29, 0x93, 0x67, 0xE8,
>> 0x23, 0x4C)
>>
>>> Which implies the text conversion should be:
>>>
>>> "92f701f6-13b4-405d-910b-299367e8234c"
>>
>> Nope.
> 
> Oops! Sorry, I misread your email... The above string is correct,
> although I do not think you need such conversion. 
> 
>> EFI 2.5 spec, Appendix A "GUID and Time Formats" defines that:
>> (NOTE, I simplified the table 225 to fit in this email)
>> ==
>> This specification also defines a standard text representation of the
>> GUID. This format is also sometimes called the “registry format”. It
>> consists of 36 characters, as follows:
>>
>> aabbccdd-eeff-gghh-iijj-kkllmmnnoopp
>>  :
>>
>> Table 225. Text representation relationships
>> String	Offset In Buffer   EFI_GUID
>> aa	3                  Data1[24:31]
>> bb      2                  Data1[16:23]
>> cc      1                  Data1[8:15]
>> dd      0                  Data1[0:7]
>>  :
>> ===
>>
>> Therefore:
>>
>> aa = Data1[21:31] = 92
>> bb = Data1[16:23] = F7
>> cc = Data1[8:15]  = 01
>> dd = Data1[0:7]   = F6
>>
>>> ...not
>>>
>>>> +#define UUID_CONTROL_REGION             "f601f792-b413-5d40-910b-299367e8234c"
>>
>> Hence, the above string is correct.
> 
> Misread again... Right, the above string is NOT correct.
> 
> I think we are on the same page that the GUID strings in this patch need
> to be changed.
> 
> { 0x92F701F6, 0x13B4, 0x405D, 0x91, 0x0B, 0x29, 0x93, 0x67, 0xE8, 0x23,
> 0x4C }
> 
> should be defined as:
> 
> "92f701f6-13b4-405d-910b-299367e8234c"

I've lost track of the right answer but should we be discussing
it in the context of this patch too?

http://www.spinics.net/lists/linux-acpi/msg57825.html
[PATCH 18/19] ACPICA: ACPI 6.0: Add support for NFIT table.

Dan's version of the file has lots of other UUIDs too, beyond NFIT.

-- ljk

> 
> Thanks,
> -Toshi
> 
> 
>> ToUUD then stores the given string to Buffer according to "Offset In
>> Buffer" in the above table.
>>
>> Another example, EFI 2.5 spec defines GPT partition GUID:
>>
>> ===
>> Table 19. Defined GPT Partition Entry - Partition Type GUIDs
>> EFI System Partition C12A7328-F81F-11D2-BA4B-00A0C93EC93B
>> ===
>>
>> The kernel defines it as:
>> #define PARTITION_SYSTEM_GUID \
>>     EFI_GUID( 0xC12A7328, 0xF81F, 0x11d2, \
>>               0xBA, 0x4B, 0x00, 0xA0, 0xC9, 0x3E, 0xC9, 0x3B)
>>
>> Thanks,
>> -Toshi
>>
>> _______________________________________________
>> Linux-nvdimm mailing list
>> Linux-nvdimm@...ts.01.org
>> https://lists.01.org/mailman/listinfo/linux-nvdimm
> 
> 
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