linux-kernel - Re: sdio: enhance IO_RW

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Date:	Mon, 06 Aug 2007 16:32:40 +0100
From:	David Vrabel <david.vrabel@....com>
To:	Pierre Ossman <drzeus-list@...eus.cx>
CC:	linux-kernel@...r.kernel.org
Subject: Re: sdio: enhance IO_RW_EXTENDED support

Pierre Ossman wrote:
> On Mon, 06 Aug 2007 11:31:19 +0100
> David Vrabel <david.vrabel@....com> wrote:
> 
>> I would expect the block size to be set once per card, and never be
>> changed and thus it's not logically a per-transfer operation.  We
>> certainly wouldn't want to change the block size willy-nilly as it's
>> an expensive operation.
>>
> 
> Indeed. It would of course be optimized so that it doesn't change the
> size needlessly.

Drivers may care about the block size though so you can't have it
changing behind their backs. e.g., they may need to pad data to a
multiple of the block size.

>>> I suspect that some transactions might require a certain block size.
>>> But we could satisfy that by stating that any transfer small enough
>>> to fit into one block will not be split up.
>> I consider it unlikely that any card would want to do anything other
>> than always use the largest possible block size.
>>
> 
> I have a counter example. I have here a Marvell wifi card which needs a
> firmware upload. And it seems to be rather picky about parameters
> during that upload.
>
> I'm still experimenting with a clean way to do things for this card.
> I'll get back to you. :)

sdio_set_block_size(func, 64); /* ew, this card is fussy */

download_firmware();

sdio_set_block_size(func, func->max_blksize); /* Ahhh, back to the
card's default */

If a card is fussy about the block size I don't think there's anything
cleaner than specifying directly in the driver.

David
-- 
David Vrabel, Software Engineer, Drivers group  Tel: +44 (0)1223 692562
CSR plc, Churchill House, Cambridge Business Park, Cowley Road, CB4 0WZ


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