linux-kernel - Re: [PATCH 1/2] regulator: core: Allow use of "status = disabled" in regulator dts nodes

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Date:	Wed, 27 Apr 2016 16:31:02 +0200
From:	Hans de Goede <hdegoede@...hat.com>
To:	Mark Brown <broonie@...nel.org>
Cc:	Liam Girdwood <lgirdwood@...il.com>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Chen-Yu Tsai <wens@...e.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] regulator: core: Allow use of "status = disabled" in
 regulator dts nodes

Hi,

On 27-04-16 16:24, Mark Brown wrote:
> On Wed, Apr 27, 2016 at 04:03:44PM +0200, Hans de Goede wrote:
>
>> So if we want to use these pins as gpio pins we must not register
>> a regulator for these pins at all, otherwise any gpio use (switching
>> to input, or writing a value) gets undone when the regulator subsys
>> disables unused regulators at the end of kernel-init.
>
> The regulator API should not touch any regulators that it doesn't have
> permission to change the state for.  All other regulators are strictly
> read only.

How do we give permission to change state ? Is omitting the dts node,
and thus not returning a node / constrains from regulator_of_get_init_data
enough for the regulator API to not have permission ?

Is there any way to see this in sysfs ?

>> This commits allows the use of  "status = disabled" in regulator dts
>> nodes and makes regulator_register return ENODEV when this is set.
>
> If the regulator can't be changed why is it in the DT in the first
> place?

The regulator is part of the pmic and the axp20x regulator driver
registers all regulators on the pmic when the pmic-s mfd instantiated
regulators-platform-device gets probed.

We do use a whole bunch of the other regulators. This patch-set
is an attempt to make the control more fine-grained then register
all / no regulators by support status=disabled in the regulator
nodes. But maybe I'm missing something and this is not necessary,
see the earlier part of this reply.

Regards,

Hans