linux-kernel - Re: [PATCH 1/4] regmap: Add generic non-memory mapped register access API

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Date:	Fri, 8 Jul 2011 22:44:24 -0700
From:	Greg KH <greg@...ah.com>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
Cc:	Dimitris Papastamos <dp@...nsource.wolfsonmicro.com>,
	Liam Girdwood <lrg@...com>,
	Samuel Oritz <sameo@...ux.intel.com>,
	Graeme Gregory <gg@...mlogic.co.uk>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] regmap: Add generic non-memory mapped register
 access API

On Sat, Jul 09, 2011 at 01:50:41PM +0900, Mark Brown wrote:
> There are many places in the tree where we implement register access for
> devices on non-memory mapped buses, especially I2C and SPI. Since hardware
> designers seem to have settled on a relatively consistent set of register
> interfaces this can be effectively factored out into shared code.  There
> are a standard set of formats for marshalling data for exchange with the
> device, with the actual I/O mechanisms generally being simple byte
> streams.
> 
> We create an abstraction for marshaling data into formats which can be
> sent on the control interfaces, and create a standard method for
> plugging in actual transport underneath that.
> 
> This is mostly a refactoring and renaming of the bottom level of the
> existing code for sharing register I/O which we have in ASoC. A
> subsequent patch in this series converts ASoC to use this.  The main
> difference in interface is that reads return values by writing to a
> location provided by a pointer rather than in the return value, ensuring
> we can use the full range of the type for register data.  We also use
> unsigned types rather than ints for the same reason.
> 
> As some of the devices can have very large register maps the existing
> ASoC code also contains infrastructure for managing register caches.
> This cache work will be moved over in a future stage to allow for
> separate review, the current patch only deals with the physical I/O.
> We also only deal with access to a single register at a time initially
> as this is the most common case.
> 
> Signed-off-by: Mark Brown <broonie@...nsource.wolfsonmicro.com>
> Acked-by: Liam Girdwood <lrg@...com>

Acked-by: Greg Kroah-Hartman <gregkh@...e.de>
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