linux-kernel - Re: regmap: Question about devices with unequal register sizes

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Date:	Mon, 06 May 2013 18:32:12 +0200
From:	Daniel Mack <zonque@...il.com>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
CC:	LKML <linux-kernel@...r.kernel.org>,
	Dimitris Papastamos <dp@...nsource.wolfsonmicro.com>
Subject: Re: regmap: Question about devices with unequal register sizes

On 17.02.2013 17:23, Mark Brown wrote:
> On Sat, Feb 16, 2013 at 06:03:51PM +0100, Daniel Mack wrote:
> 
>> The register layout is described on page 26, and they call their
>> registers 'subaddresses'. Up to sub-address 0x1c, I see no problem
>> mapping that to a simple 8-bit regmap layout, but above that, access
>> gets trickier because registers change their sizes, which breaks the cache.
> 
> The regmap I/O code isn't making any effort to support such devices, the
> hardware is just too crazy to worry about.  The best you can do is use
> the no-bus support and open code your physical I/O so you can still use
> the cache.

So it turns out I need to write these registers now on the TAS5086
codec, which has such a strange layout. I wonder how I can possibly open
code the physical I/O with registers that are up to 20 bytes in size,
while the reg_write callback in struct regmap_config assumes an unsigned
int suffices for the data? Any example you can point me to?


Thanks,
Daniel

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