linux-kernel - Re: [PATCH v4 2/6] regulator: Add regulator_of_get

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Message-ID: <ZrtB7NPmnqF5ya2A@smile.fi.intel.com>
Date: Tue, 13 Aug 2024 14:22:20 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Chen-Yu Tsai <wenst@...omium.org>
Cc: Rob Herring <robh@...nel.org>, Saravana Kannan <saravanak@...gle.com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	Wolfram Sang <wsa@...nel.org>, Benson Leung <bleung@...omium.org>,
	Tzung-Bi Shih <tzungbi@...nel.org>, Mark Brown <broonie@...nel.org>,
	Liam Girdwood <lgirdwood@...il.com>,
	chrome-platform@...ts.linux.dev, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Douglas Anderson <dianders@...omium.org>,
	Johan Hovold <johan@...nel.org>, Jiri Kosina <jikos@...nel.org>,
	linux-i2c@...r.kernel.org
Subject: Re: [PATCH v4 2/6] regulator: Add regulator_of_get_optional() for
 pure DT regulator lookup

On Thu, Aug 08, 2024 at 05:59:25PM +0800, Chen-Yu Tsai wrote:
> The to-be-introduced I2C component prober needs to enable regulator
> supplies (and toggle GPIO pins) for the various components it intends
> to probe. To support this, a new "pure DT lookup" method for getting
> regulator supplies is needed, since the device normally requesting
> the supply won't get created until after the component is probed to
> be available.
> 
> This adds a new regulator_of_get_optional() for this purpose. The
> underlying code that support the existing regulator_get*() functions
> are extended to support this specific case.

...

>  /**
>   * regulator_dev_lookup - lookup a regulator device.
>   * @dev: device for regulator "consumer".
> + * @node: device node for regulator supply lookup.
> + *        Falls back to dev->of_node if NULL.

Please, avoid using dereferences in the comments. Use plain language:
"Falls back to the OF node of the @dev, if NULL." or alike.

>   * @supply: Supply name or regulator ID.

>   */

...

>  static struct regulator_dev *regulator_dev_lookup(struct device *dev,
> +						  struct device_node *node,

This function has no of_ prefix in its name. If you want to make it for all,
please use fwnode instead. Otherwise I would expect a new one with of_ prefix.
(But I really prefer just agnostic, i.e. fwnode, approach!)

>  						  const char *supply)
>  {
> +	bool pure_dt_lookup = false;

Redundant assignment.

> +	pure_dt_lookup = (node && !dev);
>  
> +	/* Pure DT lookup should use given supply name directly */
> +	if (!pure_dt_lookup)
> +		regulator_supply_alias(&dev, &supply);
> +
> +	if (!node && dev && dev->of_node)

The dev->of_node is redundant and with the above...

> +		node = dev->of_node;

...this becomes as simple as

	if (!node && dev)

> +	/* Pure DT lookup stops here. */
> +	if (pure_dt_lookup)
> +		return ERR_PTR(-ENODEV);

Looking at this pure_dt_lookup and the above (somehow inverted) case I would
rather use (node && !dev) or (!node && dev) explicitly everywhere.

...

> +struct regulator *_regulator_get(struct device *dev, struct device_node *node,
> +				 const char *id, enum regulator_get_type get_type)

Again, no of_ prefix and function becomes OF-specific...

-- 
With Best Regards,
Andy Shevchenko