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.
[[email protected]: Proposal and initial implementation] Signed-off-by: Thomas Abraham <[email protected]> --- 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 _______________________________________________ devicetree-discuss mailing list [email protected] https://lists.ozlabs.org/listinfo/devicetree-discuss
