Commit a3b85363 authored by Thomas Abraham's avatar Thomas Abraham Committed by Grant Likely
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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: default avatarThomas Abraham <thomas.abraham@linaro.org>
[grant.likely: some word smithing and be more defensive validating the string]
Signed-off-by: default avatarGrant Likely <grant.likely@secretlab.ca>
parent 7423734e

drivers/of/base.c

+58 −0
Original line number Diff line number Diff line
@@ -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

include/linux/of.h

+4 −0
Original line number Diff line number Diff line
@@ -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);

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