From a3b853633d78c3930b513ee219df48637ac82eed Mon Sep 17 00:00:00 2001 From: Thomas Abraham Date: Thu, 30 Jun 2011 21:26:10 +0530 Subject: [PATCH] dt: add helper functions to read u32 and string property values Add helper functions to retrieve 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@secretlab.ca: Proposal and initial implementation] Signed-off-by: Thomas Abraham [grant.likely: some word smithing and be more defensive validating the string] Signed-off-by: Grant Likely --- drivers/of/base.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++ include/linux/of.h | 4 ++++ 2 files changed, 62 insertions(+) diff --git a/drivers/of/base.c b/drivers/of/base.c index 632ebae7f17..b8b65fddbeb 100644 --- a/drivers/of/base.c +++ b/drivers/of/base.c @@ -595,6 +595,64 @@ struct device_node *of_find_node_by_phandle(phandle handle) } EXPORT_SYMBOL(of_find_node_by_phandle); +/** + * of_property_read_u32 - Find and read a 32 bit integer from a property + * @np: device node from which the property value is to be read. + * @propname: name of the property to be searched. + * @out_value: pointer to return value, modified only if return value is 0. + * + * Search for a property in a device node and read a 32-bit value from + * it. Returns 0 on success, -EINVAL if the property does not exist, + * -ENODATA if property does not have a value, and -EOVERFLOW if the + * property data isn't large enough. + * + * 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 and read a string from a property + * @np: device node from which the property value is to be read. + * @propname: name of the property to be searched. + * @out_string: pointer to null terminated return string, modified only if + * return value is 0. + * + * Search for a property in a device tree node and retrieve a null + * terminated string value (pointer to data, not a copy). Returns 0 on + * success, -EINVAL if the property does not exist, -ENODATA if property + * does not have a value, and -EILSEQ if the string is not null-terminated + * within the length of the property data. + * + * The out_string pointer 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 diff --git a/include/linux/of.h b/include/linux/of.h index bfc0ed1b0ce..4fc4c1b8d5d 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); -- 2.39.2