linux-kernel - Re: question about concurrent regmap i2c usage

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Date:   Tue, 4 Apr 2017 13:26:54 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Michael Hennerich <michael.hennerich@...log.com>
Cc:     linus.walleij@...aro.org, wsa@...-dreams.de,
        linux-gpio@...r.kernel.org, linux-i2c@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: question about concurrent regmap i2c usage

On Tue, Apr 04, 2017 at 10:28:23AM +0200, Michael Hennerich wrote:

> A question came up, regarding whether it's recommended to mix regmap_i2c and
> plain i2c_smbus or direct adapter transfers.

> In this specific case for the i2c MUX portion we need to avoid double locks,
> and therefore use un-locked direct adapter transfers.

> The same time we also implement a small gpiochip, where we would like to use
> regmap to avoid some boilerplate code for the register cache.

That should work fine providing nothing tries to change cached registers
underneath the regmap.  regmap won't be able to tell anything's changed
otherwise.

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