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

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Message-ID: <20130217162337.GB1583@opensource.wolfsonmicro.com>
Date:	Sun, 17 Feb 2013 16:23:38 +0000
From:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
To:	Daniel Mack <zonque@...il.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 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.

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