linux-kernel - Re: [PATCH v4 1/7] mfd: add syscon driver based on regmap

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Date:	Fri, 31 Aug 2012 09:26:29 +0800
From:	Shawn Guo <shawn.guo@...aro.org>
To:	Dong Aisheng <b29396@...escale.com>
CC:	<linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linus.walleij@...ricsson.com>, <s.hauer@...gutronix.de>,
	<kernel@...gutronix.de>, <grant.likely@...retlab.ca>,
	<rob.herring@...xeda.com>, <sameo@...ux.intel.com>, <lrg@...com>,
	<broonie@...nsource.wolfsonmicro.com>,
	<richard.zhao@...escale.com>,
	<devicetree-discuss@...ts.ozlabs.org>, <swarren@...dotorg.org>
Subject: Re: [PATCH v4 1/7] mfd: add syscon driver based on regmap

On Wed, Aug 29, 2012 at 06:56:52PM +0800, Dong Aisheng wrote:
> +config MFD_SYSCON
> +        bool "System Controller Register R/W Based on Regmap"

If the driver only compiles and works for device tree probe, we should
have the following?

	depends on OF

> +        select REGMAP_MMIO
> +        help
> +	  Select this option to enable accessing system control registers
> +	  via regmap.
> +

<snip>

> +struct regmap *syscon_node_to_regmap(struct device_node *np)
> +{
> +	struct syscon *syscon;
> +	struct device *dev;
> +
> +	dev = driver_find_device(&syscon_driver.driver, NULL, np,
> +				 syscon_match);
> +	of_node_put(np);

This looks a little unnatural to me.  Function syscon_node_to_regmap
becomes an API visible to clients, who might never know that np will
be put inside the API.  I'm saying the client may also call of_node_put
to put the node they get.

I think of_node_put should be moved out from here and put into
syscon_node_to_regmap and syscon_regmap_lookup_by_compatible.

Regards,
Shawn

> +
> +	if (!dev)
> +		return ERR_PTR(-EPROBE_DEFER);
> +
> +	syscon = dev_get_drvdata(dev);
> +
> +	return syscon->regmap;
> +}
> +EXPORT_SYMBOL_GPL(syscon_node_to_regmap);
> +
> +struct regmap *syscon_regmap_lookup_by_compatible(const char *s)
> +{
> +	struct device_node *syscon_np;
> +
> +	syscon_np = of_find_compatible_node(NULL, NULL, s);
> +	if (!syscon_np)
> +		return ERR_PTR(-ENODEV);
> +
> +	return syscon_node_to_regmap(syscon_np);
> +}
> +EXPORT_SYMBOL_GPL(syscon_regmap_lookup_by_compatible);
> +
> +struct regmap *syscon_regmap_lookup_by_phandle(struct device_node *np,
> +					const char *property)
> +{
> +	struct device_node *syscon_np;
> +
> +	syscon_np = of_parse_phandle(np, property, 0);
> +	if (!syscon_np)
> +		return ERR_PTR(-ENODEV);
> +
> +	return syscon_node_to_regmap(syscon_np);
> +}
> +EXPORT_SYMBOL_GPL(syscon_regmap_lookup_by_phandle);

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