Re: [PATCH v2 1/4] of: reserved_mem: Add functions to parse "memory-region"

[Arnaud POULIQUEN <arnaud.pouliquen@foss.st.com>]

Hello Rob,

On 4/23/25 21:42, Rob Herring (Arm) wrote:
> Drivers with "memory-region" properties currently have to do their own
> parsing of "memory-region" properties. The result is all the drivers
> have similar patterns of a call to parse "memory-region" and then get
> the region's address and size. As this is a standard property, it should
> have common functions for drivers to use. Add new functions to count the
> number of regions and retrieve the region's address as a resource.
> 
> Reviewed-by: Daniel Baluta <daniel.baluta@nxp.com>
> Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
> ---
> v2:
>  - Wrap function parameters
> ---
>  drivers/of/of_reserved_mem.c    | 80 +++++++++++++++++++++++++++++++++++++++++
>  include/linux/of_reserved_mem.h | 26 ++++++++++++++
>  2 files changed, 106 insertions(+)
> 
> diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
> index ee2e31522d7e..f87915cce961 100644
> --- a/drivers/of/of_reserved_mem.c
> +++ b/drivers/of/of_reserved_mem.c
> @@ -12,6 +12,7 @@
>  #define pr_fmt(fmt)	"OF: reserved mem: " fmt
>  
>  #include <linux/err.h>
> +#include <linux/ioport.h>
>  #include <linux/libfdt.h>
>  #include <linux/of.h>
>  #include <linux/of_fdt.h>
> @@ -740,3 +741,82 @@ struct reserved_mem *of_reserved_mem_lookup(struct device_node *np)
>  	return NULL;
>  }
>  EXPORT_SYMBOL_GPL(of_reserved_mem_lookup);
> +
> +/**
> + * of_reserved_mem_region_to_resource() - Get a reserved memory region as a resource
> + * @np:		node containing 'memory-region' property
> + * @idx:	index of 'memory-region' property to lookup
> + * @res:	Pointer to a struct resource to fill in with reserved region
> + *
> + * This function allows drivers to lookup a node's 'memory-region' property
> + * entries by index and return a struct resource for the entry.
> + *
> + * Returns 0 on success with @res filled in. Returns -ENODEV if 'memory-region'
> + * is missing or unavailable, -EINVAL for any other error.
> + */
> +int of_reserved_mem_region_to_resource(const struct device_node *np,
> +				       unsigned int idx, struct resource *res)
> +{
> +	struct reserved_mem *rmem;
> +
> +	if (!np)
> +		return -EINVAL;
> +
> +	struct device_node __free(device_node) *target = of_parse_phandle(np, "memory-region", idx);
> +	if (!target || !of_device_is_available(target))
> +		return -ENODEV;
> +
> +	rmem = of_reserved_mem_lookup(target);
> +	if (!rmem)
> +		return -EINVAL;
> +
> +	resource_set_range(res, rmem->base, rmem->size);
> +	res->name = rmem->name;
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(of_reserved_mem_region_to_resource);
> +
> +/**
> + * of_reserved_mem_region_to_resource_byname() - Get a reserved memory region as a resource
> + * @np:		node containing 'memory-region' property
> + * @name:	name of 'memory-region' property entry to lookup
> + * @res:	Pointer to a struct resource to fill in with reserved region
> + *
> + * This function allows drivers to lookup a node's 'memory-region' property
> + * entries by name and return a struct resource for the entry.
> + *
> + * Returns 0 on success with @res filled in. Returns -ENODEV if 'memory-region'
> + * is missing or unavailable, -EINVAL for any other error.

of_property_match_string() can return some other error values.

Thanks,
Arnaud

> + */
> +int of_reserved_mem_region_to_resource_byname(const struct device_node *np,
> +					      const char *name,
> +					      struct resource *res)
> +{
> +	int idx;
> +
> +	if (!name)
> +		return -EINVAL;
> +
> +	idx = of_property_match_string(np, "memory-region-names", name);
> +	if (idx < 0)
> +		return idx;
> +
> +	return of_reserved_mem_region_to_resource(np, idx, res);
> +}
> +EXPORT_SYMBOL_GPL(of_reserved_mem_region_to_resource_byname);
> +
> +/**
> + * of_reserved_mem_region_count() - Return the number of 'memory-region' entries
> + * @np:		node containing 'memory-region' property
> + *
> + * This function allows drivers to retrieve the number of entries for a node's
> + * 'memory-region' property.
> + *
> + * Returns the number of entries on success, or negative error code on a
> + * malformed property.
> + */
> +int of_reserved_mem_region_count(const struct device_node *np)
> +{
> +	return of_count_phandle_with_args(np, "memory-region", NULL);
> +}
> +EXPORT_SYMBOL_GPL(of_reserved_mem_region_count);
> diff --git a/include/linux/of_reserved_mem.h b/include/linux/of_reserved_mem.h
> index e338282da652..f573423359f4 100644
> --- a/include/linux/of_reserved_mem.h
> +++ b/include/linux/of_reserved_mem.h
> @@ -7,6 +7,7 @@
>  
>  struct of_phandle_args;
>  struct reserved_mem_ops;
> +struct resource;
>  
>  struct reserved_mem {
>  	const char			*name;
> @@ -39,6 +40,12 @@ int of_reserved_mem_device_init_by_name(struct device *dev,
>  void of_reserved_mem_device_release(struct device *dev);
>  
>  struct reserved_mem *of_reserved_mem_lookup(struct device_node *np);
> +int of_reserved_mem_region_to_resource(const struct device_node *np,
> +				       unsigned int idx, struct resource *res);
> +int of_reserved_mem_region_to_resource_byname(const struct device_node *np,
> +					      const char *name, struct resource *res);
> +int of_reserved_mem_region_count(const struct device_node *np);
> +
>  #else
>  
>  #define RESERVEDMEM_OF_DECLARE(name, compat, init)			\
> @@ -63,6 +70,25 @@ static inline struct reserved_mem *of_reserved_mem_lookup(struct device_node *np
>  {
>  	return NULL;
>  }
> +
> +static inline int of_reserved_mem_region_to_resource(const struct device_node *np,
> +						     unsigned int idx,
> +						     struct resource *res)
> +{
> +	return -ENOSYS;
> +}
> +
> +static inline int of_reserved_mem_region_to_resource_byname(const struct device_node *np,
> +							    const char *name,
> +							    struct resource *res)
> +{
> +	return -ENOSYS;
> +}
> +
> +static inline int of_reserved_mem_region_count(const struct device_node *np)
> +{
> +	return 0;
> +}
>  #endif
>  
>  /**
>