linux-kernel - Re: [PATCH 0/3] Migrate i8255 GPIO drivers to regmap API

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Date:   Wed, 9 Nov 2022 15:35:06 -0500
From:   William Breathitt Gray <william.gray@...aro.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     linus.walleij@...aro.org, brgl@...ev.pl,
        linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/3] Migrate i8255 GPIO drivers to regmap API

On Mon, Nov 07, 2022 at 12:37:00PM +0200, Andy Shevchenko wrote:
> On Thu, Nov 03, 2022 at 07:20:46AM -0400, William Breathitt Gray wrote:
> > The regmap API supports IO port accessors so we can take advantage of
> > regmap abstractions rather than handling access to the device registers
> > directly in the driver.
> > 
> > Precursor patches are provided for 104-dio-48e and 104-idi-48 to migrate
> > their respective device-specific registers first in order to simplify
> > the subsequent patch migrating the i8255 library and its dependents.
> > 
> > The struct i8255 control_state member serves as a cache of the i8255
> > device's control register. Does the regmap API support caching such that
> > we won't need to manually update a control_state member?
> 
> Yes, regmap supports caching and IIRC it's opt-out.

Looks like it's disabled by default if I understand correctly: the
cache_type member of struct regmap_config has a default value of
REGCACHE_NONE if not explicitly set. I'll set cache_type to enable
caching and remove the control_state member in v2 then.

William Breathitt Gray

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