linux-kernel - Re: [PATCH] printk: Export struct log size and member offsets through vmcoreinfo

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Message-ID: <CAPXgP13W_aqky++LkHeHBUzKFTYNiTJQpchpHLCVDAdYihu5ig@mail.gmail.com>
Date:	Fri, 20 Jul 2012 11:23:10 +0200
From:	Kay Sievers <kay@...y.org>
To:	Vivek Goyal <vgoyal@...hat.com>
Cc:	linux kernel mailing list <linux-kernel@...r.kernel.org>,
	Kexec Mailing List <kexec@...ts.infradead.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Kroah-Hartmann <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] printk: Export struct log size and member offsets through vmcoreinfo

On Thu, Jul 19, 2012 at 4:08 PM, Vivek Goyal <vgoyal@...hat.com> wrote:
> On Thu, Jul 19, 2012 at 09:57:36AM -0400, Vivek Goyal wrote:
>> On Thu, Jul 19, 2012 at 11:38:57AM +0200, Kay Sievers wrote:

>> > If we would swap the 5 + 3 bit field byte declaration, and add
>> > __packed, we can still not rely on the level to be consistently the
>> > lower 3 bits of the byte, right?
>
> I think I missed your point in last response. Are you saying that retain
> bit fields  for flags and level, and add __packed() and that will make sure
> level bits are always lowest 3bits?

It was more a question, I don't know how reliable that would be.

> I am really not sure how that is going
> to work. Also if you want to add more fields to struct log down the line,
> it will be a problem to determine the offset of byte where level bits are
> stored.

I guess, we could make sure that it's always the lowest 3 bits of a
byte. But the question if that is safe to do at all still remains. :)

Kay
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