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From: David Daney <ddaney-M3mlKVOIwJVv6pq1l3V1OdBPR1lH4CV8@public.gmane.org>
To: Ard Biesheuvel
	<ard.biesheuvel-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>,
	Lukas Wunner <lukas-JFq808J9C/izQB+pC5nmwQ@public.gmane.org>
Cc: Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>,
	"linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
	<linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	Ashok Raj <ashok.raj-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
	linux-pci <linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	Huang Ying <ying.huang-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Subject: Re: [PATCH] efi/cper: Fix endianness of PCI class code
Date: Thu, 11 May 2017 07:48:52 -0700	[thread overview]
Message-ID: <2d5f9331-6f31-2584-9ec1-2447163c6611@caviumnetworks.com> (raw)
In-Reply-To: <CAKv+Gu81gvNL1jkb3T35=-5fr_x-BmSg9X2CcQ97xv5JTZ-c1A-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>

On 05/11/2017 07:06 AM, Ard Biesheuvel wrote:
> On 10 May 2017 at 09:41, Lukas Wunner <lukas-JFq808J9C/izQB+pC5nmwQ@public.gmane.org> wrote:
>> On Wed, May 10, 2017 at 09:03:11AM +0100, Ard Biesheuvel wrote:
[...]
>>
>> It seems clumsy and unnecessary to me so I'd prefer the bitfield.
>> Please excuse my stubbornness.
>>
> 
> Stubbornness alone is not going to convince me. What *could* convince
> me (although unlikely) is a quote from the C spec which explains why
> it is 100% legal to make assumptions about how bitfields are projected
> onto byte locations in memory.

I don't think you will find that in the C specifications.

Structure layout is specified per-architecture/per-ABI so for the Linux 
kernel you would only have to check that it is strongly specified and 
compatible across `ls arch | wc -l` different architectures.  If you 
want to get started with MIPS, for example, you could look in the 
"SYSTEM V APPLICATION BINARY INTERFACE MIPS(r) RISC Processor Supplement 
3rd Edition" starting on page 3-7.  For x86 and arm{,64} I am sure you 
could find similar specifications.

David Daney

WARNING: multiple messages have this Message-ID (diff)
From: David Daney <ddaney@caviumnetworks.com>
To: Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Lukas Wunner <lukas@wunner.de>
Cc: Arnd Bergmann <arnd@arndb.de>,
	"linux-efi@vger.kernel.org" <linux-efi@vger.kernel.org>,
	Ashok Raj <ashok.raj@intel.com>,
	linux-pci <linux-pci@vger.kernel.org>,
	Huang Ying <ying.huang@intel.com>
Subject: Re: [PATCH] efi/cper: Fix endianness of PCI class code
Date: Thu, 11 May 2017 07:48:52 -0700	[thread overview]
Message-ID: <2d5f9331-6f31-2584-9ec1-2447163c6611@caviumnetworks.com> (raw)
In-Reply-To: <CAKv+Gu81gvNL1jkb3T35=-5fr_x-BmSg9X2CcQ97xv5JTZ-c1A@mail.gmail.com>

On 05/11/2017 07:06 AM, Ard Biesheuvel wrote:
> On 10 May 2017 at 09:41, Lukas Wunner <lukas@wunner.de> wrote:
>> On Wed, May 10, 2017 at 09:03:11AM +0100, Ard Biesheuvel wrote:
[...]
>>
>> It seems clumsy and unnecessary to me so I'd prefer the bitfield.
>> Please excuse my stubbornness.
>>
> 
> Stubbornness alone is not going to convince me. What *could* convince
> me (although unlikely) is a quote from the C spec which explains why
> it is 100% legal to make assumptions about how bitfields are projected
> onto byte locations in memory.

I don't think you will find that in the C specifications.

Structure layout is specified per-architecture/per-ABI so for the Linux 
kernel you would only have to check that it is strongly specified and 
compatible across `ls arch | wc -l` different architectures.  If you 
want to get started with MIPS, for example, you could look in the 
"SYSTEM V APPLICATION BINARY INTERFACE MIPS(r) RISC Processor Supplement 
3rd Edition" starting on page 3-7.  For x86 and arm{,64} I am sure you 
could find similar specifications.

David Daney

  parent reply	other threads:[~2017-05-11 14:48 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-05-05 18:38 [PATCH] efi/cper: Fix endianness of PCI class code Lukas Wunner
2017-05-05 18:38 ` Lukas Wunner
     [not found] ` <771bc335fb5856792d086ae7db288dcf244cb4cd.1493964354.git.lukas-JFq808J9C/izQB+pC5nmwQ@public.gmane.org>
2017-05-06  7:46   ` Ard Biesheuvel
2017-05-06  7:46     ` Ard Biesheuvel
2017-05-06  9:07     ` Lukas Wunner
2017-05-10  8:03       ` Ard Biesheuvel
2017-05-10  8:12         ` Arnd Bergmann
2017-05-10  8:41         ` Lukas Wunner
2017-05-11 14:06           ` Ard Biesheuvel
     [not found]             ` <CAKv+Gu81gvNL1jkb3T35=-5fr_x-BmSg9X2CcQ97xv5JTZ-c1A-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-05-11 14:48               ` David Daney [this message]
2017-05-11 14:48                 ` David Daney
2017-05-25 12:30               ` Lukas Wunner
2017-05-25 12:30                 ` Lukas Wunner
     [not found]                 ` <20170525123047.GA4172-JFq808J9C/izQB+pC5nmwQ@public.gmane.org>
2017-05-25 12:36                   ` Ard Biesheuvel
2017-05-25 12:36                     ` Ard Biesheuvel
     [not found]                     ` <CAKv+Gu_3vYKGOrzC8+Y3QwXOtV8Tbm8HC7nzQCdKVB1Qbdoriw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-05-25 12:44                       ` Lukas Wunner
2017-05-25 12:44                         ` Lukas Wunner
2017-05-25 12:47                         ` Ard Biesheuvel
2017-05-25 12:56                           ` Lukas Wunner
     [not found]                             ` <20170525125650.GA4196-JFq808J9C/izQB+pC5nmwQ@public.gmane.org>
2017-05-25 13:07                               ` Ard Biesheuvel
2017-05-25 13:07                                 ` Ard Biesheuvel
2017-05-26  6:08                                 ` Lukas Wunner
2017-05-26  8:01                                   ` Arnd Bergmann
2017-05-26 10:45                                     ` Lukas Wunner
2017-05-26  9:16                                   ` Ard Biesheuvel
     [not found]                                     ` <CAKv+Gu_fbNSK+LuWmQGqLHtu3rF9BdYwNB+K-myNXS=X+goXkQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-05-26 10:43                                       ` Lukas Wunner
2017-05-26 10:43                                         ` Lukas Wunner

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