linux-kernel - Re: [PATCH] regulator: core: Limit propagation of parent voltage count and list

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Message-ID: <20170324203818.GA33073@google.com>
Date:   Fri, 24 Mar 2017 13:38:19 -0700
From:   Brian Norris <briannorris@...omium.org>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Javier Martinez Canillas <javier@....samsung.com>,
        linux-kernel@...r.kernel.org,
        Douglas Anderson <dianders@...omium.org>
Subject: Re: [PATCH] regulator: core: Limit propagation of parent voltage
 count and list

On Fri, Mar 24, 2017 at 01:09:52PM -0700, Matthias Kaehlcke wrote:
> diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
> index 53d4fc70dbd0..121838e0125b 100644
> --- a/drivers/regulator/core.c
> +++ b/drivers/regulator/core.c
> @@ -2487,6 +2487,10 @@ static int _regulator_list_voltage(struct regulator *regulator,
>  		if (lock)
>  			mutex_unlock(&rdev->mutex);
>  	} else if (rdev->supply) {
> +		// Limit propagation of parent values to switch regulators

The kernel doesn't use C99 comments. Oddly enough, this isn't actually
in the coding style doc (Documentation/process/coding-style.rst), nor is
it caught by scripts/checkpatch.pl (even though it clearly has a 'C99
comment' rule).

> +		if (ops->get_voltage || ops->get_voltage_sel)
> +			return -EINVAL;
> +
>  		ret = _regulator_list_voltage(rdev->supply, selector, lock);
>  	} else {
>  		return -EINVAL;
> @@ -2540,6 +2544,7 @@ EXPORT_SYMBOL_GPL(regulator_is_enabled);
>  int regulator_count_voltages(struct regulator *regulator)
>  {
>  	struct regulator_dev	*rdev = regulator->rdev;
> +	const struct regulator_ops *ops = rdev->desc->ops;
>  
>  	if (rdev->desc->n_voltages)
>  		return rdev->desc->n_voltages;
> @@ -2547,6 +2552,10 @@ int regulator_count_voltages(struct regulator *regulator)
>  	if (!rdev->supply)
>  		return -EINVAL;
>  
> +	// Limit propagation of parent value to switch regulators

Same here.

> +	if (ops->get_voltage || ops->get_voltage_sel || ops->list_voltage)
> +		return -EINVAL;
> +
>  	return regulator_count_voltages(rdev->supply);
>  }
>  EXPORT_SYMBOL_GPL(regulator_count_voltages);

I'm not very familiar with this code, but judging by your problem
description in previous threads and by comparing with the logic in
_regulator_get_voltage() (for when to reference the ->supply), this
seems resonable. So:

Reviewed-by: Brian Norris <briannorris@...omium.org>

It's probably worth verifying that this doesn't break whatever Javier
was supporting in the first place, as a sanity check.

Brian