linux-kernel - Re: [PATCH] regmap: allow to disable all locking mechanisms

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Message-ID: <CAHp75VfSe33bnTymjoTOMPMdXntne9FCn7EvWxY4NJeh=0+Ykg@mail.gmail.com>
Date:   Sun, 10 Dec 2017 15:10:31 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Bartosz Golaszewski <brgl@...ev.pl>
Cc:     Mark Brown <broonie@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] regmap: allow to disable all locking mechanisms

On Wed, Dec 6, 2017 at 4:26 PM, Bartosz Golaszewski <brgl@...ev.pl> wrote:
> We have a use case in the at24 EEPROM driver (recently converted to
> using regmap instead of raw i2c/smbus calls) where we read from/write
> to the regmap in a loop, while protecting the entire loop with
> a mutex.
>
> Currently this implicitly makes us use two mutexes - one in the driver
> and one in regmap. While browsing the code for similar use cases I
> noticed a significant number of places where locking *seems* redundant.
>
> Allow users to completely disable any locking mechanisms in regmap
> config.

> +static void regmap_lock_unlock_empty(void *__map)

..._none()?


> +{
> +
> +}
> +
>  static void regmap_lock_mutex(void *__map)

> -       if (config->lock && config->unlock) {
> +       if (config->disable_locking) {
> +               map->lock = map->unlock = regmap_lock_unlock_empty;
> +       } else if (config->lock && config->unlock) {

Why not to introduce positive switch, namely
 bool mutex_lock; // choose better name
and assign ..._none() by default?

-- 
With Best Regards,
Andy Shevchenko