linux-kernel - Re: [PATCH V1] regmap: Support for caching in reg_raw

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Message-ID: <20120210155831.GE6472@opensource.wolfsonmicro.com>
Date:	Fri, 10 Feb 2012 15:58:32 +0000
From:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
To:	Lars-Peter Clausen <lars@...afoo.de>
Cc:	Laxman Dewangan <ldewangan@...dia.com>, gregkh@...uxfoundation.org,
	linux-kernel@...r.kernel.org, linux-tegra@...r.kernel.org
Subject: Re: [PATCH V1] regmap: Support for caching in reg_raw_write()

On Fri, Feb 10, 2012 at 01:33:16PM +0100, Lars-Peter Clausen wrote:

> regmap_write doesn't always go the raw_write path. Also with this approach

We can ignore the non-byte formats as a wart for this; they're cut out
of this area of the subsystem functionality and just get single register
write operatons with single register cache access.

> we end up formatting the value into the raw format, only to parse it again
> in the next step.

Yes, like I say there's room for optimisation.  For 8 bit values there
would be win from working out that we don't need to do anything at all, 
though I doubt it's ever going to be performance critical.

> Furthermore I don't think it makes sense to cache raw values as the cache
> operates on a register level, not on a byte level.

The entire API operates on registers really.  The only reason
raw_write() takes a length is because it's what most of the users are
actually likely to have to hand, trying to write to less than a register
isn't particularly sensible.

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