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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 <thomas.abraham@linaro.org>
[grant.likely: some word smithing and be more defensive validating the string]
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
hifive-unleashed-5.1
Thomas Abraham 2011-06-30 21:26:10 +05:30 committed by Grant Likely
parent 7423734e19
commit a3b853633d
2 changed files with 62 additions and 0 deletions
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58
drivers/of/base.c
View File

@ -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

4
include/linux/of.h
View File

@ -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);