Re: [PATCH v4] of: add functions to count number of elements in a property

Rob Herring
2014-01-18T15:07:34Z

On Sat, Jan 18, 2014 at 6:02 AM, Heiko Stübner <heiko@sntech.de> wrote:
> The need to know the number of array elements in a property is
> a common pattern. To prevent duplication of open-coded implementations
> add a helper static function that also centralises strict sanity
> checking and DTB format details, as well as a set of wrapper functions
> for u8, u16, u32 and u64.
>
> Suggested-by: Mark Rutland <mark.rutland@arm.com>
> Signed-off-by: Heiko Stuebner <heiko@sntech.de>
> ---

Looks good. Do you plan to convert some users to use this?

Rob

> changes since v3:
> address more comments from Rob Herring
> - export the base function and inline the type-specific wrappers
> changes since v2:
> address more comments from Mark Rutland
> - switch to of_property_count_elems_of_size
> - use full_name instead of name in error message
> changes since v1:
> address comments from Rob Herring and Mark Rutland:
> - provide a helper and a set of wrappers for u8-u64
> - get rid of extra len variable, prop->length is enough
> - include node name in error message
>
> Mark, does your Reviewed-by holds for this variant too?
>
> drivers/of/base.c | 32 ++++++++++++++++++++++
> include/linux/of.h | 76 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 108 insertions(+)
>
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index f807d0e..21646c0 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -862,6 +862,38 @@ struct device_node *of_find_node_by_phandle(phandle handle)
> EXPORT_SYMBOL(of_find_node_by_phandle);
>
> /**
> + * of_property_count_elems_of_size - Count the number of elements in a property
> + *
> + * @np: device node from which the property value is to be read.
> + * @propname: name of the property to be searched.
> + * @elem_size: size of the individual element
> + *
> + * Search for a property in a device node and count the number of elements of
> + * size elem_size in it. Returns number of elements on sucess, -EINVAL if the
> + * property does not exist or its length does not match a multiple of u16 and
> + * -ENODATA if the property does not have a value.
> + */
> +int of_property_count_elems_of_size(const struct device_node *np,
> + const char *propname, int elem_size)
> +{
> + struct property *prop = of_find_property(np, propname, NULL);
> +
> + if (!prop)
> + return -EINVAL;
> + if (!prop->value)
> + return -ENODATA;
> +
> + if (prop->length % elem_size != 0) {
> + pr_err("size of %s in node %s is not a multiple of %d\n",
> + propname, np->full_name, elem_size);
> + return -EINVAL;
> + }
> +
> + return prop->length / elem_size;
> +}
> +EXPORT_SYMBOL_GPL(of_property_count_elems_of_size);
> +
> +/**
> * of_find_property_value_of_size
> *
> * @np: device node from which the property value is to be read.
> diff --git a/include/linux/of.h b/include/linux/of.h
> index 276c546..293920d 100644
> --- a/include/linux/of.h
> +++ b/include/linux/of.h
> @@ -250,6 +250,8 @@ extern struct device_node *of_find_node_with_property(
> extern struct property *of_find_property(const struct device_node *np,
> const char *name,
> int *lenp);
> +extern int of_property_count_elems_of_size(const struct device_node *np,
> + const char *propname, int elem_size);
> extern int of_property_read_u32_index(const struct device_node *np,
> const char *propname,
> u32 index, u32 *out_value);
> @@ -426,6 +428,12 @@ static inline struct device_node *of_find_compatible_node(
> return NULL;
> }
>
> +static inline int of_property_count_elems_of_size(const struct device_node *np,
> + const char *propname, int elem_size)
> +{
> + return -ENOSYS;
> +}
> +
> static inline int of_property_read_u32_index(const struct device_node *np,
> const char *propname, u32 index, u32 *out_value)
> {
> @@ -565,6 +573,74 @@ static inline int of_node_to_nid(struct device_node *device) { return 0; }
> #endif
>
> /**
> + * of_property_count_u8_elems - Count the number of u8 elements in a property
> + *
> + * @np: device node from which the property value is to be read.
> + * @propname: name of the property to be searched.
> + *
> + * Search for a property in a device node and count the number of u8 elements
> + * in it. Returns number of elements on sucess, -EINVAL if the property does
> + * not exist or its length does not match a multiple of u8 and -ENODATA if the
> + * property does not have a value.
> + */
> +static inline int of_property_count_u8_elems(const struct device_node *np,
> + const char *propname)
> +{
> + return of_property_count_elems_of_size(np, propname, sizeof(u8));
> +}
> +
> +/**
> + * of_property_count_u16_elems - Count the number of u16 elements in a property
> + *
> + * @np: device node from which the property value is to be read.
> + * @propname: name of the property to be searched.
> + *
> + * Search for a property in a device node and count the number of u16 elements
> + * in it. Returns number of elements on sucess, -EINVAL if the property does
> + * not exist or its length does not match a multiple of u16 and -ENODATA if the
> + * property does not have a value.
> + */
> +static inline int of_property_count_u16_elems(const struct device_node *np,
> + const char *propname)
> +{
> + return of_property_count_elems_of_size(np, propname, sizeof(u16));
> +}
> +
> +/**
> + * of_property_count_u32_elems - Count the number of u32 elements in a property
> + *
> + * @np: device node from which the property value is to be read.
> + * @propname: name of the property to be searched.
> + *
> + * Search for a property in a device node and count the number of u32 elements
> + * in it. Returns number of elements on sucess, -EINVAL if the property does
> + * not exist or its length does not match a multiple of u32 and -ENODATA if the
> + * property does not have a value.
> + */
> +static inline int of_property_count_u32_elems(const struct device_node *np,
> + const char *propname)
> +{
> + return of_property_count_elems_of_size(np, propname, sizeof(u32));
> +}
> +
> +/**
> + * of_property_count_u64_elems - Count the number of u64 elements in a property
> + *
> + * @np: device node from which the property value is to be read.
> + * @propname: name of the property to be searched.
> + *
> + * Search for a property in a device node and count the number of u64 elements
> + * in it. Returns number of elements on sucess, -EINVAL if the property does
> + * not exist or its length does not match a multiple of u64 and -ENODATA if the
> + * property does not have a value.
> + */
> +static inline int of_property_count_u64_elems(const struct device_node *np,
> + const char *propname)
> +{
> + return of_property_count_elems_of_size(np, propname, sizeof(u64));
> +}
> +
> +/**
> * of_property_read_bool - Findfrom a property
> * @np: device node from which the property value is to be read.
> * @propname: name of the property to be searched.
> --
> 1.7.10.4
>
>