Re: [PATCH] of: add function to count number of u32 elements in a property

Rob Herring
2014-01-17T14:29:10Z

On Thu, Jan 16, 2014 at 12:04 PM, 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 function that also centralises strict sanity checking
> and DTB format details.
>
> Suggested-by: Mark Rutland <mark.rutland@arm.com>
> Signed-off-by: Heiko Stuebner <heiko@sntech.de>
> ---
> Hi Mark,
> did you mean it like this? I've tested it with the sram-reserve change and
> it made the part of the determining the number elements a lot nicer :-)
>
> drivers/of/base.c | 32 ++++++++++++++++++++++++++++++++
> include/linux/of.h | 8 ++++++++
> 2 files changed, 40 insertions(+)
>
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index f807d0e..0f40ea5 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -920,6 +920,38 @@ int of_property_read_u32_index(const struct device_node *np,
> EXPORT_SYMBOL_GPL(of_property_read_u32_index);
>
> /**
> + * of_property_count_u32_elems - Count the number of u32 values 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.
> + */
> +int of_property_count_u32_elems(const struct device_node *np,
> + const char *propname)
> +{
> + int elem_size = sizeof(u32);

This should be a parameter, so functions for different sized
properties can be a simple wrapper function.

> + int len;
> + struct property *prop = of_find_property(np, propname, &len);
> +
> + if (!prop)
> + return -EINVAL;
> + if (!prop->value)
> + return -ENODATA;
> +
> + if (prop->length % elem_size != 0) {
> + pr_err("size of %s is not a multiple of u32\n", propname);

The node name would be useful here too.

> + return -EINVAL;
> + }
> +
> + return len / elem_size;
> +}
> +EXPORT_SYMBOL_GPL(of_property_count_u32_elems);
> +
> +/**
> * of_property_read_u8_array - Find and read an array of u8 from a property.
> *
> * @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..5794942 100644
> --- a/include/linux/of.h
> +++ b/include/linux/of.h
> @@ -253,6 +253,8 @@ extern struct property *of_find_property(const struct device_node *np,
> extern int of_property_read_u32_index(const struct device_node *np,
> const char *propname,
> u32 index, u32 *out_value);
> +extern int of_property_count_u32_elems(const struct device_node *np,
> + const char *propname);
> extern int of_property_read_u8_array(const struct device_node *np,
> const char *propname, u8 *out_values, size_t sz);
> extern int of_property_read_u16_array(const struct device_node *np,
> @@ -432,6 +434,12 @@ static inline int of_property_read_u32_index(const struct device_node *np,
> return -ENOSYS;
> }
>
> +static inline int of_property_count_u32_elems(const struct device_node *np,
> + const char *propname)
> +{
> + return -ENOSYS;
> +}
> +
> static inline int of_property_read_u8_array(const struct device_node *np,
> const char *propname, u8 *out_values, size_t sz)
> {
> --
> 1.7.10.4
>
>