linux-kernel - Re: [PATCH 3/4] EFI: Add support for variables longer than 1024 bytes

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Message-ID: <CAGTjWtA5_Xk6EMF6UmTTfWGCM+3imoGXn5awP4ANM4w=NgO=-Q@mail.gmail.com>
Date:	Wed, 14 Dec 2011 15:24:36 -0800
From:	Mike Waychison <mikew@...gle.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Matthew Garrett <mjg59@...f.ucam.org>,
	linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH 3/4] EFI: Add support for variables longer than 1024 bytes

On Wed, Dec 14, 2011 at 3:22 PM, H. Peter Anvin <hpa@...or.com> wrote:
> On 12/14/2011 03:06 PM, Mike Waychison wrote:
>> On Wed, Dec 14, 2011 at 3:00 PM, H. Peter Anvin <hpa@...or.com> wrote:
>>> On 12/14/2011 02:57 PM, Mike Waychison wrote:
>>>>
>>>> Well,l we could *not* support returning all the data field for
>>>> datasize > 1024, and simply truncate the field.  We are limited by
>>>> PAGE_SIZE by sysfs here anyway (so we don't really want to have a
>>>> variable size memcpy in efivar_show_raw).
>>>>
>>>
>>> That may be the biggest reason to avoid sysfs.  As far as I know sysfs
>>> doesn't allow seq_file to be used.
>>>
>>
>> Completely agreed.  I don't think a seq_file is warranted in this case
>> in particular, but the dummification of the interfaces in sysfs sure
>> makes it hard to do anything that isn't a "single value string".
>>
>
> Well, seq_file is a good way to deal with arbitrary length data.
>

seq_file maps well to arbitrary record counts (keeping records
self-consistent), but not so well for arbitrarily large records.
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