linux-kernel - Re: [RFC 06/18] regmap: Formalise use of non-bus context

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Date:	Thu, 09 Jan 2014 13:08:31 +0000
From:	Pawel Moll <pawel.moll@....com>
To:	Mark Brown <broonie@...nel.org>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Arnd Bergmann <arnd@...db.de>, Jon Medhurst <tixy@...aro.org>,
	"arm@...nel.org" <arm@...nel.org>, Olof Johansson <olof@...om.net>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [RFC 06/18] regmap: Formalise use of non-bus context

On Tue, 2013-12-24 at 12:45 +0000, Mark Brown wrote:
> I'd note that I wasn't CCed on most of this series so I'm not entirely
> sure what it's trying to do.

Apologies. The series is quite long and I didn't want to bother too many
people with mostly irrelevant changes. Will copy you on the whole thing
next time.

> > Bus-less maps (ones with reg_read and reg_write functions
> > defined in regmap_config) were given the context passed
> > in regmap_init(), but it was still called "bus_context".
> > 
> > This patch formalises this aspect by renaming it to simple
> > "context" and adds the missing link, free_context function
> > in regmap_config, which allows bus-less maps to use the
> > context in classic way.
> 
> This should be two patches, one patch to do the rename and one to add
> the operation.  

Sure, will do.

> The obvious question here is why is this callback useful
> - what is being allocated in a regmap specific context that needs to be
> lifetime managed separately to the thing doing the creation?  I can't
> see any obvious reason why this would ever get used.

First of all, it's just a generalization of the free_context already
existing in regmap_bus (and used by regmap-mmio). And in case of this
series it is being used to release extra resource added allocated for a
"busless" regmap_config. Briefly, I'm using devm_regmap_init() to
"attach" a custom regmap configuration to a device when it is being
created (which is then dev_get_regmap()-ed in the driver, as you saw in
the regulator patch) and its context is a pointer to kzallocated data.
free_context is used to release it when devm resource is being removed.

Does it make any sense?

Paweł

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