[PATCH 01/17] mfd: syscon: Add reference counting and device managed support

[Simon Horman]

On Tue, Apr 30, 2024 at 10:37:10AM +0200, Herve Codina wrote:
> From: Clément Léger <clement.leger at bootlin.com>
> 
> Syscon releasing is not supported.
> Without release function, unbinding a driver that uses syscon whether
> explicitly or due to a module removal left the used syscon in a in-use
> state.
> 
> For instance a syscon_node_to_regmap() call from a consumer retrieve a
> syscon regmap instance. Internally, syscon_node_to_regmap() can create
> syscon instance and add it to the existing syscon list. No API is
> available to release this syscon instance, remove it from the list and
> free it when it is not used anymore.
> 
> Introduce reference counting in syscon in order to keep track of syscon
> usage using syscon_{get,put}() and add a device managed version of
> syscon_regmap_lookup_by_phandle(), to automatically release the syscon
> instance on the consumer removal.
> 
> Signed-off-by: Clément Léger <clement.leger at bootlin.com>
> Signed-off-by: Herve Codina <herve.codina at bootlin.com>

...

> diff --git a/include/linux/mfd/syscon.h b/include/linux/mfd/syscon.h
> index c315903f6dab..164b9bcb49c3 100644
> --- a/include/linux/mfd/syscon.h
> +++ b/include/linux/mfd/syscon.h
> @@ -15,6 +15,7 @@
>  #include <linux/errno.h>
>  
>  struct device_node;
> +struct device;
>  
>  #ifdef CONFIG_MFD_SYSCON
>  struct regmap *device_node_to_regmap(struct device_node *np);
> @@ -28,6 +29,11 @@ struct regmap *syscon_regmap_lookup_by_phandle_args(struct device_node *np,
>  						    unsigned int *out_args);
>  struct regmap *syscon_regmap_lookup_by_phandle_optional(struct device_node *np,
>  							const char *property);
> +void syscon_put_regmap(struct regmap *regmap);
> +
> +struct regmap *devm_syscon_regmap_lookup_by_phandle(struct device *dev,
> +						    struct device_node *np,
> +						    const char *property);
>  #else
>  static inline struct regmap *device_node_to_regmap(struct device_node *np)
>  {
> @@ -67,6 +73,18 @@ static inline struct regmap *syscon_regmap_lookup_by_phandle_optional(
>  	return NULL;
>  }
>  
> +static intline void syscon_put_regmap(struct regmap *regmap)

intline -> inline

> +{
> +}

...