linux-kernel - Re: [RFC PATCH v4 3/5] PCI: Check platform specific ECAM quirks

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Date:	Wed, 29 Jun 2016 15:52:04 +0200
From:	Tomasz Nowicki <tn@...ihalf.com>
To:	Christopher Covington <cov@...eaurora.org>,
	Duc Dang <dhdang@....com>
Cc:	Bjorn Helgaas <helgaas@...nel.org>, Arnd Bergmann <arnd@...db.de>,
	Will Deacon <will.deacon@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	Rafael Wysocki <rafael@...nel.org>,
	Hanjun Guo <hanjun.guo@...aro.org>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	Sinan Kaya <okaya@...eaurora.org>,
	Jayachandran C <jchandra@...adcom.com>,
	Robert Richter <robert.richter@...iumnetworks.com>,
	Marcin Wojtas <mw@...ihalf.com>,
	Liviu Dudau <Liviu.Dudau@....com>,
	David Daney <ddaney@...iumnetworks.com>,
	Yijing Wang <wangyijing@...wei.com>,
	Mark Salter <msalter@...hat.com>, linux-pci@...r.kernel.org,
	linux-arm <linux-arm-kernel@...ts.infradead.org>,
	linux-acpi@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linaro-acpi@...ts.linaro.org, Jon Masters <jcm@...hat.com>,
	Andrea Gallo <andrea.gallo@...aro.org>, jeremy.linton@....com,
	Dongdong Liu <liudongdong3@...wei.com>,
	Gabriele Paoloni <gabriele.paoloni@...wei.com>,
	Jeffrey Hugo <jhugo@...eaurora.org>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>
Subject: Re: [RFC PATCH v4 3/5] PCI: Check platform specific ECAM quirks

On 29.06.2016 15:34, Christopher Covington wrote:
> I'm confused by this statement. OEMID is defined as 6 bytes long and OEM
> Table ID as 8 bytes long in the ACPI specification. As far as I can
> tell, if your string isn't exactly that long, padding up to that length
> is required.

Well, I cannot find that requirement in ACPI spec. but I might missed 
something.

I dumped my x86 machine ACPI tables and here is an example of MCFG:

$ cat mcfg.dsl
/*
  * Intel ACPI Component Architecture
  * AML/ASL+ Disassembler version 20160108-64
  * Copyright (c) 2000 - 2016 Intel Corporation
  *
  * Disassembly of mcfg.dat, Wed Jun 29 15:48:16 2016
  *
  * ACPI Data Table [MCFG]
  *
  * Format: [HexOffset DecimalOffset ByteLength]  FieldName : FieldValue
  */

[000h 0000   4]                    Signature : "MCFG"    [Memory Mapped 
Configuration table]
[004h 0004   4]                 Table Length : 0000003C
[008h 0008   1]                     Revision : 01
[009h 0009   1]                     Checksum : A9
[00Ah 0010   6]                       Oem ID : "ALASKA"
[010h 0016   8]                 Oem Table ID : "A M I"
[018h 0024   4]                 Oem Revision : 01072009
[01Ch 0028   4]              Asl Compiler ID : "MSFT"
[020h 0032   4]        Asl Compiler Revision : 00000097

[024h 0036   8]                     Reserved : 0000000000000000

[02Ch 0044   8]                 Base Address : 00000000F8000000
[034h 0052   2]         Segment Group Number : 0000
[036h 0054   1]             Start Bus Number : 00
[037h 0055   1]               End Bus Number : 3F
[038h 0056   4]                     Reserved : 00000000

Raw Table Data: Length 60 (0x3C)

00000000  4d 43 46 47 3c 00 00 00  01 a9 41 4c 41 53 4b 41 
|MCFG<.....ALASKA|
00000010  41 20 4d 20 49 00 00 00  09 20 07 01 4d 53 46 54  |A M I.... 
..MSFT|
00000020  97 00 00 00 00 00 00 00  00 00 00 00 00 00 00 f8 
|................|
00000030  00 00 00 00 00 00 00 3f  00 00 00 00              |.......?....|

So in this example I have OEM table ID "A M I" 6 character long and 0 
padding.

Tomasz