[PATCH] dt: add helper functions to read u32 and string property values

[Grant Likely]

On Thu, Jun 30, 2011 at 09:26:10PM +0530, Thomas Abraham wrote:
> Add helper functions to retrive unsigned integer and string property values from
> properties of a device node. These helper functions can be used to lookup a
> property in a device node, perform error checking and read the property value.
> 
> [grant.likely at secretlab.ca: Proposal and initial implementation]
> Signed-off-by: Thomas Abraham <thomas.abraham at linaro.org>

Merged, thanks.  Bonus points to anyone who submits patches converting
existing code to this new api.

g.

> ---
>  drivers/of/base.c  |   59 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/of.h |    4 +++
>  2 files changed, 63 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index 632ebae..4823b53 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -596,6 +596,65 @@ struct device_node *of_find_node_by_phandle(phandle handle)
>  EXPORT_SYMBOL(of_find_node_by_phandle);
>  
>  /**
> + * of_property_read_u32 - Find a property in a device node and read the
> + *				32-bit property value
> + * @np:		device node from which the property value is to be read.
> + * @propname:	name of the property to be searched.
> + * @out_value:	returned value, valid if return value is 0.
> + *
> + * Search for a property in a device node and read a 32-bit value from a
> + * property. Returns -EINVAL, if the property does not exist, -ENODATA, if
> + * property does not have a value, -EOVERFLOW, if the property data isn't
> + * large enough, and 0 on success.
> + *
> + * The out_value is modified only if a valid u32 value can be decoded.
> + */
> +int of_property_read_u32(struct device_node *np, char *propname, u32 *out_value)
> +{
> +	struct property *prop = of_find_property(np, propname, NULL);
> +
> +	if (!prop)
> +		return -EINVAL;
> +	if (!prop->value)
> +		return -ENODATA;
> +	if (sizeof(*out_value) > prop->length)
> +		return -EOVERFLOW;
> +	*out_value = be32_to_cpup(prop->value);
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(of_property_read_u32);
> +
> +/**
> + * of_property_read_string - Find a property in a device node and return a
> + *				pointer to the property string value.
> + * @np:		device node from which the property value is to be read.
> + * @propname:	name of the property to be searched.
> + * @out_string:	pointer to a null terminated string, valid only if the return
> + *		value is 0.
> + *
> + * Returns a pointer to a null terminated property value string. Returns
> + * -EINVAL, if the property does not exist, -ENODATA, if property does not have
> + * a value, -EILSEQ, if the string is not null-terminated within the length of
> + * the property value, and 0 on success.
> + *
> + * The out_string value is modified only if a valid string can be decoded.
> + */
> +int of_property_read_string(struct device_node *np, char *propname,
> +				char **out_string)
> +{
> +	struct property *prop = of_find_property(np, propname, NULL);
> +	if (!prop)
> +		return -EINVAL;
> +	if (!prop->value)
> +		return -ENODATA;
> +	if (strnlen(prop->value, prop->length) == prop->length)
> +		return -EILSEQ;
> +	*out_string = prop->value;
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(of_property_read_string);
> +
> +/**
>   * of_parse_phandle - Resolve a phandle property to a device_node pointer
>   * @np: Pointer to device node holding phandle property
>   * @phandle_name: Name of property holding a phandle value
> diff --git a/include/linux/of.h b/include/linux/of.h
> index bfc0ed1..4fc4c1b 100644
> --- a/include/linux/of.h
> +++ b/include/linux/of.h
> @@ -195,6 +195,10 @@ 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_read_u32(struct device_node *np, char *propname,
> +					u32 *out_value);
> +extern int of_property_read_string(struct device_node *np, char *propname,
> +					char **out_string);
>  extern int of_device_is_compatible(const struct device_node *device,
>  				   const char *);
>  extern int of_device_is_available(const struct device_node *device);
> -- 
> 1.6.6.rc2
>