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Message-ID: <48205B0D.70202@seznam.cz>
Date: Tue, 06 May 2008 15:20:13 +0200
From: Michal Simek <monstr@...nam.cz>
To: Arnd Bergmann <arnd@...db.de>
CC: Geert Uytterhoeven <geert@...ux-m68k.org>,
Michal Simek <monstr@...nam.cz>,
John Williams <john.williams@...alogix.com>,
linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
stephen.neuendorffer@...inx.com, John.Linn@...inx.com,
matthew@....cx, will.newton@...il.com, drepper@...hat.com,
microblaze-uclinux@...e.uq.edu.au, grant.likely@...retlab.ca
Subject: Re: [PATCH 36/56] microblaze_v2: dma support
Hi all,
here is proposed struct.
struct scatterlist {
dma_addr_t dma_address;
unsigned long page_link;
#ifdef CONFIG_DEBUG_SG
unsigned long sg_magic;
#endif
unsigned int length;
unsigned int offset;
};
Is it OK now?
Michal
>>> struct scatterlist {
>>> unsigned long page_link;
>>> unsigned int offset;
>>> unsigned int length;
>>> dma_addr_t dma_address;
>>> };
>> If unsigned long is 32-bit but dma_addr_t is 64-bit, there may be a gap
>> between length and dma_address.
>>
>
> But moving dma_address to the front only has the effect to create implicit
> padding at the end of struct scatterlist, so you don't gain anything
> either way.
>
> It's only an internal definition that can be changed at any time without
> breaking applications, so I wouldn't worry about it, and better leave
> it identical to the other architectures.
>
> The one thing that should indeed be changed is the addition of
> 'unsigned long sg_magic' that is needed for CONFIG_DEBUG_SG.
>
> Arnd <><
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