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dm: core: Add livetree access functions

Add a basic assortment of functions to access the live device tree. These
come from Linux v4.9 and are modified for U-Boot to the minimum extent
possible. While these functions are now very stable in Linux, it will be
possible to merge in fixes if needed.

Signed-off-by: Simon Glass <sjg@chromium.org>
tags/2020-06-01
Simon Glass 4 years ago
parent
commit
644ec0a933
3 changed files with 1083 additions and 0 deletions
  1. +1
    -0
      drivers/core/Makefile
  2. +735
    -0
      drivers/core/of_access.c
  3. +347
    -0
      include/dm/of_access.h

+ 1
- 0
drivers/core/Makefile View File

@@ -11,3 +11,4 @@ obj-$(CONFIG_$(SPL_)SIMPLE_BUS) += simple-bus.o
obj-$(CONFIG_DM) += dump.o
obj-$(CONFIG_$(SPL_)REGMAP) += regmap.o
obj-$(CONFIG_$(SPL_)SYSCON) += syscon-uclass.o
obj-$(CONFIG_OF_LIVE) += of_access.o

+ 735
- 0
drivers/core/of_access.c View File

@@ -0,0 +1,735 @@
/*
* Originally from Linux v4.9
* Paul Mackerras August 1996.
* Copyright (C) 1996-2005 Paul Mackerras.
*
* Adapted for 64bit PowerPC by Dave Engebretsen and Peter Bergner.
* {engebret|bergner}@us.ibm.com
*
* Adapted for sparc and sparc64 by David S. Miller davem@davemloft.net
*
* Reconsolidated from arch/x/kernel/prom.c by Stephen Rothwell and
* Grant Likely.
*
* Modified for U-Boot
* Copyright (c) 2017 Google, Inc
*
* This file follows drivers/of/base.c with functions in the same order as the
* Linux version.
*
* SPDX-License-Identifier: GPL-2.0+
*/

#include <common.h>
#include <libfdt.h>
#include <dm/of_access.h>
#include <linux/ctype.h>
#include <linux/err.h>
#include <linux/ioport.h>

DECLARE_GLOBAL_DATA_PTR;

/* list of struct alias_prop aliases */
LIST_HEAD(aliases_lookup);

/* "/aliaes" node */
static struct device_node *of_aliases;

/* "/chosen" node */
static struct device_node *of_chosen;

/* node pointed to by the stdout-path alias */
static struct device_node *of_stdout;

/* pointer to options given after the alias (separated by :) or NULL if none */
static const char *of_stdout_options;

/**
* struct alias_prop - Alias property in 'aliases' node
*
* The structure represents one alias property of 'aliases' node as
* an entry in aliases_lookup list.
*
* @link: List node to link the structure in aliases_lookup list
* @alias: Alias property name
* @np: Pointer to device_node that the alias stands for
* @id: Index value from end of alias name
* @stem: Alias string without the index
*/
struct alias_prop {
struct list_head link;
const char *alias;
struct device_node *np;
int id;
char stem[0];
};

int of_n_addr_cells(const struct device_node *np)
{
const __be32 *ip;

do {
if (np->parent)
np = np->parent;
ip = of_get_property(np, "#address-cells", NULL);
if (ip)
return be32_to_cpup(ip);
} while (np->parent);

/* No #address-cells property for the root node */
return OF_ROOT_NODE_ADDR_CELLS_DEFAULT;
}

int of_n_size_cells(const struct device_node *np)
{
const __be32 *ip;

do {
if (np->parent)
np = np->parent;
ip = of_get_property(np, "#size-cells", NULL);
if (ip)
return be32_to_cpup(ip);
} while (np->parent);

/* No #size-cells property for the root node */
return OF_ROOT_NODE_SIZE_CELLS_DEFAULT;
}

struct property *of_find_property(const struct device_node *np,
const char *name, int *lenp)
{
struct property *pp;

if (!np)
return NULL;

for (pp = np->properties; pp; pp = pp->next) {
if (strcmp(pp->name, name) == 0) {
if (lenp)
*lenp = pp->length;
break;
}
}
if (!pp && lenp)
*lenp = -FDT_ERR_NOTFOUND;

return pp;
}

struct device_node *of_find_all_nodes(struct device_node *prev)
{
struct device_node *np;

if (!prev) {
np = gd->of_root;
} else if (prev->child) {
np = prev->child;
} else {
/*
* Walk back up looking for a sibling, or the end of the
* structure
*/
np = prev;
while (np->parent && !np->sibling)
np = np->parent;
np = np->sibling; /* Might be null at the end of the tree */
}

return np;
}

const void *of_get_property(const struct device_node *np, const char *name,
int *lenp)
{
struct property *pp = of_find_property(np, name, lenp);

return pp ? pp->value : NULL;
}

static const char *of_prop_next_string(struct property *prop, const char *cur)
{
const void *curv = cur;

if (!prop)
return NULL;

if (!cur)
return prop->value;

curv += strlen(cur) + 1;
if (curv >= prop->value + prop->length)
return NULL;

return curv;
}

int of_device_is_compatible(const struct device_node *device,
const char *compat, const char *type,
const char *name)
{
struct property *prop;
const char *cp;
int index = 0, score = 0;

/* Compatible match has highest priority */
if (compat && compat[0]) {
prop = of_find_property(device, "compatible", NULL);
for (cp = of_prop_next_string(prop, NULL); cp;
cp = of_prop_next_string(prop, cp), index++) {
if (of_compat_cmp(cp, compat, strlen(compat)) == 0) {
score = INT_MAX/2 - (index << 2);
break;
}
}
if (!score)
return 0;
}

/* Matching type is better than matching name */
if (type && type[0]) {
if (!device->type || of_node_cmp(type, device->type))
return 0;
score += 2;
}

/* Matching name is a bit better than not */
if (name && name[0]) {
if (!device->name || of_node_cmp(name, device->name))
return 0;
score++;
}

return score;
}

bool of_device_is_available(const struct device_node *device)
{
const char *status;
int statlen;

if (!device)
return false;

status = of_get_property(device, "status", &statlen);
if (status == NULL)
return true;

if (statlen > 0) {
if (!strcmp(status, "okay"))
return true;
}

return false;
}

struct device_node *of_get_parent(const struct device_node *node)
{
const struct device_node *np;

if (!node)
return NULL;

np = of_node_get(node->parent);

return (struct device_node *)np;
}

static struct device_node *__of_get_next_child(const struct device_node *node,
struct device_node *prev)
{
struct device_node *next;

if (!node)
return NULL;

next = prev ? prev->sibling : node->child;
for (; next; next = next->sibling)
if (of_node_get(next))
break;
of_node_put(prev);
return next;
}

#define __for_each_child_of_node(parent, child) \
for (child = __of_get_next_child(parent, NULL); child != NULL; \
child = __of_get_next_child(parent, child))

static struct device_node *__of_find_node_by_path(struct device_node *parent,
const char *path)
{
struct device_node *child;
int len;

len = strcspn(path, "/:");
if (!len)
return NULL;

__for_each_child_of_node(parent, child) {
const char *name = strrchr(child->full_name, '/');

name++;
if (strncmp(path, name, len) == 0 && (strlen(name) == len))
return child;
}
return NULL;
}

#define for_each_property_of_node(dn, pp) \
for (pp = dn->properties; pp != NULL; pp = pp->next)

struct device_node *of_find_node_opts_by_path(const char *path,
const char **opts)
{
struct device_node *np = NULL;
struct property *pp;
const char *separator = strchr(path, ':');

if (opts)
*opts = separator ? separator + 1 : NULL;

if (strcmp(path, "/") == 0)
return of_node_get(gd->of_root);

/* The path could begin with an alias */
if (*path != '/') {
int len;
const char *p = separator;

if (!p)
p = strchrnul(path, '/');
len = p - path;

/* of_aliases must not be NULL */
if (!of_aliases)
return NULL;

for_each_property_of_node(of_aliases, pp) {
if (strlen(pp->name) == len && !strncmp(pp->name, path,
len)) {
np = of_find_node_by_path(pp->value);
break;
}
}
if (!np)
return NULL;
path = p;
}

/* Step down the tree matching path components */
if (!np)
np = of_node_get(gd->of_root);
while (np && *path == '/') {
struct device_node *tmp = np;

path++; /* Increment past '/' delimiter */
np = __of_find_node_by_path(np, path);
of_node_put(tmp);
path = strchrnul(path, '/');
if (separator && separator < path)
break;
}

return np;
}

struct device_node *of_find_compatible_node(struct device_node *from,
const char *type, const char *compatible)
{
struct device_node *np;

for_each_of_allnodes_from(from, np)
if (of_device_is_compatible(np, compatible, type, NULL) &&
of_node_get(np))
break;
of_node_put(from);

return np;
}

struct device_node *of_find_node_by_phandle(phandle handle)
{
struct device_node *np;

if (!handle)
return NULL;

for_each_of_allnodes(np)
if (np->phandle == handle)
break;
(void)of_node_get(np);

return np;
}

/**
* of_find_property_value_of_size() - find property of given size
*
* Search for a property in a device node and validate the requested size.
*
* @np: device node from which the property value is to be read.
* @propname: name of the property to be searched.
* @len: requested length of property value
*
* @return the property value 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.
*/
static void *of_find_property_value_of_size(const struct device_node *np,
const char *propname, u32 len)
{
struct property *prop = of_find_property(np, propname, NULL);

if (!prop)
return ERR_PTR(-EINVAL);
if (!prop->value)
return ERR_PTR(-ENODATA);
if (len > prop->length)
return ERR_PTR(-EOVERFLOW);

return prop->value;
}

int of_read_u32(const struct device_node *np, const char *propname, u32 *outp)
{
const __be32 *val;

debug("%s: %s: ", __func__, propname);
if (!np)
return -EINVAL;
val = of_find_property_value_of_size(np, propname, sizeof(*outp));
if (IS_ERR(val)) {
debug("(not found)\n");
return PTR_ERR(val);
}

*outp = be32_to_cpup(val);
debug("%#x (%d)\n", *outp, *outp);

return 0;
}

int of_read_u32_array(const struct device_node *np, const char *propname,
u32 *out_values, size_t sz)
{
const __be32 *val;

debug("%s: %s: ", __func__, propname);
val = of_find_property_value_of_size(np, propname,
sz * sizeof(*out_values));

if (IS_ERR(val))
return PTR_ERR(val);

debug("size %zd\n", sz);
while (sz--)
*out_values++ = be32_to_cpup(val++);

return 0;
}

int of_property_match_string(const struct device_node *np, const char *propname,
const char *string)
{
const struct property *prop = of_find_property(np, propname, NULL);
size_t l;
int i;
const char *p, *end;

if (!prop)
return -EINVAL;
if (!prop->value)
return -ENODATA;

p = prop->value;
end = p + prop->length;

for (i = 0; p < end; i++, p += l) {
l = strnlen(p, end - p) + 1;
if (p + l > end)
return -EILSEQ;
debug("comparing %s with %s\n", string, p);
if (strcmp(string, p) == 0)
return i; /* Found it; return index */
}
return -ENODATA;
}

/**
* of_property_read_string_helper() - Utility helper for parsing string properties
* @np: device node from which the property value is to be read.
* @propname: name of the property to be searched.
* @out_strs: output array of string pointers.
* @sz: number of array elements to read.
* @skip: Number of strings to skip over at beginning of list.
*
* Don't call this function directly. It is a utility helper for the
* of_property_read_string*() family of functions.
*/
int of_property_read_string_helper(const struct device_node *np,
const char *propname, const char **out_strs,
size_t sz, int skip)
{
const struct property *prop = of_find_property(np, propname, NULL);
int l = 0, i = 0;
const char *p, *end;

if (!prop)
return -EINVAL;
if (!prop->value)
return -ENODATA;
p = prop->value;
end = p + prop->length;

for (i = 0; p < end && (!out_strs || i < skip + sz); i++, p += l) {
l = strnlen(p, end - p) + 1;
if (p + l > end)
return -EILSEQ;
if (out_strs && i >= skip)
*out_strs++ = p;
}
i -= skip;
return i <= 0 ? -ENODATA : i;
}

static int __of_parse_phandle_with_args(const struct device_node *np,
const char *list_name,
const char *cells_name,
int cell_count, int index,
struct of_phandle_args *out_args)
{
const __be32 *list, *list_end;
int rc = 0, cur_index = 0;
uint32_t count = 0;
struct device_node *node = NULL;
phandle phandle;
int size;

/* Retrieve the phandle list property */
list = of_get_property(np, list_name, &size);
if (!list)
return -ENOENT;
list_end = list + size / sizeof(*list);

/* Loop over the phandles until all the requested entry is found */
while (list < list_end) {
rc = -EINVAL;
count = 0;

/*
* If phandle is 0, then it is an empty entry with no
* arguments. Skip forward to the next entry.
*/
phandle = be32_to_cpup(list++);
if (phandle) {
/*
* Find the provider node and parse the #*-cells
* property to determine the argument length.
*
* This is not needed if the cell count is hard-coded
* (i.e. cells_name not set, but cell_count is set),
* except when we're going to return the found node
* below.
*/
if (cells_name || cur_index == index) {
node = of_find_node_by_phandle(phandle);
if (!node) {
debug("%s: could not find phandle\n",
np->full_name);
goto err;
}
}

if (cells_name) {
if (of_read_u32(node, cells_name, &count)) {
debug("%s: could not get %s for %s\n",
np->full_name, cells_name,
node->full_name);
goto err;
}
} else {
count = cell_count;
}

/*
* Make sure that the arguments actually fit in the
* remaining property data length
*/
if (list + count > list_end) {
debug("%s: arguments longer than property\n",
np->full_name);
goto err;
}
}

/*
* All of the error cases above bail out of the loop, so at
* this point, the parsing is successful. If the requested
* index matches, then fill the out_args structure and return,
* or return -ENOENT for an empty entry.
*/
rc = -ENOENT;
if (cur_index == index) {
if (!phandle)
goto err;

if (out_args) {
int i;
if (WARN_ON(count > OF_MAX_PHANDLE_ARGS))
count = OF_MAX_PHANDLE_ARGS;
out_args->np = node;
out_args->args_count = count;
for (i = 0; i < count; i++)
out_args->args[i] =
be32_to_cpup(list++);
} else {
of_node_put(node);
}

/* Found it! return success */
return 0;
}

of_node_put(node);
node = NULL;
list += count;
cur_index++;
}

/*
* Unlock node before returning result; will be one of:
* -ENOENT : index is for empty phandle
* -EINVAL : parsing error on data
* [1..n] : Number of phandle (count mode; when index = -1)
*/
rc = index < 0 ? cur_index : -ENOENT;
err:
if (node)
of_node_put(node);
return rc;
}

struct device_node *of_parse_phandle(const struct device_node *np,
const char *phandle_name, int index)
{
struct of_phandle_args args;

if (index < 0)
return NULL;

if (__of_parse_phandle_with_args(np, phandle_name, NULL, 0, index,
&args))
return NULL;

return args.np;
}

int of_parse_phandle_with_args(const struct device_node *np,
const char *list_name, const char *cells_name,
int index, struct of_phandle_args *out_args)
{
if (index < 0)
return -EINVAL;

return __of_parse_phandle_with_args(np, list_name, cells_name, 0,
index, out_args);
}

static void of_alias_add(struct alias_prop *ap, struct device_node *np,
int id, const char *stem, int stem_len)
{
ap->np = np;
ap->id = id;
strncpy(ap->stem, stem, stem_len);
ap->stem[stem_len] = 0;
list_add_tail(&ap->link, &aliases_lookup);
debug("adding DT alias:%s: stem=%s id=%i node=%s\n",
ap->alias, ap->stem, ap->id, of_node_full_name(np));
}

int of_alias_scan(void)
{
struct property *pp;

of_aliases = of_find_node_by_path("/aliases");
of_chosen = of_find_node_by_path("/chosen");
if (of_chosen == NULL)
of_chosen = of_find_node_by_path("/chosen@0");

if (of_chosen) {
const char *name;

name = of_get_property(of_chosen, "stdout-path", NULL);
if (name)
of_stdout = of_find_node_opts_by_path(name,
&of_stdout_options);
}

if (!of_aliases)
return 0;

for_each_property_of_node(of_aliases, pp) {
const char *start = pp->name;
const char *end = start + strlen(start);
struct device_node *np;
struct alias_prop *ap;
ulong id;
int len;

/* Skip those we do not want to proceed */
if (!strcmp(pp->name, "name") ||
!strcmp(pp->name, "phandle") ||
!strcmp(pp->name, "linux,phandle"))
continue;

np = of_find_node_by_path(pp->value);
if (!np)
continue;

/*
* walk the alias backwards to extract the id and work out
* the 'stem' string
*/
while (isdigit(*(end-1)) && end > start)
end--;
len = end - start;

if (strict_strtoul(end, 10, &id) < 0)
continue;

/* Allocate an alias_prop with enough space for the stem */
ap = malloc(sizeof(*ap) + len + 1);
if (!ap)
return -ENOMEM;
memset(ap, 0, sizeof(*ap) + len + 1);
ap->alias = start;
of_alias_add(ap, np, id, start, len);
}

return 0;
}

int of_alias_get_id(const struct device_node *np, const char *stem)
{
struct alias_prop *app;
int id = -ENODEV;

mutex_lock(&of_mutex);
list_for_each_entry(app, &aliases_lookup, link) {
if (strcmp(app->stem, stem) != 0)
continue;

if (np == app->np) {
id = app->id;
break;
}
}
mutex_unlock(&of_mutex);

return id;
}

struct device_node *of_get_stdout(void)
{
return of_stdout;
}

+ 347
- 0
include/dm/of_access.h View File

@@ -0,0 +1,347 @@
/*
* Originally from Linux v4.9
* Copyright (C) 1996-2005 Paul Mackerras.
*
* Updates for PPC64 by Peter Bergner & David Engebretsen, IBM Corp.
* Updates for SPARC64 by David S. Miller
* Derived from PowerPC and Sparc prom.h files by Stephen Rothwell, IBM Corp.
*
* Copyright (c) 2017 Google, Inc
* Written by Simon Glass <sjg@chromium.org>
*
* Modified for U-Boot
* Copyright (c) 2017 Google, Inc
*
* SPDX-License-Identifier: GPL-2.0+
*/

#ifndef _DM_OF_ACCESS_H
#define _DM_OF_ACCESS_H

#include <dm/of.h>

/**
* of_find_all_nodes - Get next node in global list
* @prev: Previous node or NULL to start iteration
* of_node_put() will be called on it
*
* Returns a node pointer with refcount incremented, use
* of_node_put() on it when done.
*/
struct device_node *of_find_all_nodes(struct device_node *prev);

#define for_each_of_allnodes_from(from, dn) \
for (dn = of_find_all_nodes(from); dn; dn = of_find_all_nodes(dn))
#define for_each_of_allnodes(dn) for_each_of_allnodes_from(NULL, dn)

/* Dummy functions to mirror Linux. These are not used in U-Boot */
#define of_node_get(x) (x)
static inline void of_node_put(const struct device_node *np) { }

/**
* of_n_addr_cells() - Get the number of address cells for a node
*
* This walks back up the tree to find the closest #address-cells property
* which controls the given node.
*
* @np: Node pointer to check
* @return number of address cells this node uses
*/
int of_n_addr_cells(const struct device_node *np);

/**
* of_n_size_cells() - Get the number of size cells for a node
*
* This walks back up the tree to find the closest #size-cells property
* which controls the given node.
*
* @np: Node pointer to check
* @return number of size cells this node uses
*/
int of_n_size_cells(const struct device_node *np);

/**
* of_find_property() - find a property in a node
*
* @np: Pointer to device node holding property
* @name: Name of property
* @lenp: If non-NULL, returns length of property
* @return pointer to property, or NULL if not found
*/
struct property *of_find_property(const struct device_node *np,
const char *name, int *lenp);

/**
* of_get_property() - get a property value
*
* Find a property with a given name for a given node and return the value.
*
* @np: Pointer to device node holding property
* @name: Name of property
* @lenp: If non-NULL, returns length of property
* @return pointer to property value, or NULL if not found
*/
const void *of_get_property(const struct device_node *np, const char *name,
int *lenp);

/**
* of_device_is_compatible() - Check if the node matches given constraints
* @device: pointer to node
* @compat: required compatible string, NULL or "" for any match
* @type: required device_type value, NULL or "" for any match
* @name: required node name, NULL or "" for any match
*
* Checks if the given @compat, @type and @name strings match the
* properties of the given @device. A constraints can be skipped by
* passing NULL or an empty string as the constraint.
*
* @return 0 for no match, and a positive integer on match. The return
* value is a relative score with larger values indicating better
* matches. The score is weighted for the most specific compatible value
* to get the highest score. Matching type is next, followed by matching
* name. Practically speaking, this results in the following priority
* order for matches:
*
* 1. specific compatible && type && name
* 2. specific compatible && type
* 3. specific compatible && name
* 4. specific compatible
* 5. general compatible && type && name
* 6. general compatible && type
* 7. general compatible && name
* 8. general compatible
* 9. type && name
* 10. type
* 11. name
*/
int of_device_is_compatible(const struct device_node *np, const char *compat,
const char *type, const char *name);

/**
* of_device_is_available() - check if a device is available for use
*
* @device: Node to check for availability
*
* @return true if the status property is absent or set to "okay", false
* otherwise
*/
bool of_device_is_available(const struct device_node *np);

/**
* of_get_parent() - Get a node's parent, if any
*
* @node: Node to check
* @eturns a node pointer, or NULL if none
*/
struct device_node *of_get_parent(const struct device_node *np);

/**
* of_find_node_opts_by_path() - Find a node matching a full OF path
*
* @path: Either the full path to match, or if the path does not start with
* '/', the name of a property of the /aliases node (an alias). In the
* case of an alias, the node matching the alias' value will be returned.
* @opts: Address of a pointer into which to store the start of an options
* string appended to the end of the path with a ':' separator. Can be NULL
*
* Valid paths:
* /foo/bar Full path
* foo Valid alias
* foo/bar Valid alias + relative path
*
* @return a node pointer or NULL if not found
*/
struct device_node *of_find_node_opts_by_path(const char *path,
const char **opts);

static inline struct device_node *of_find_node_by_path(const char *path)
{
return of_find_node_opts_by_path(path, NULL);
}

/**
* of_find_compatible_node() - find a node based on its compatible string
*
* Find a node based on type and one of the tokens in its "compatible" property
* @from: Node to start searching from or NULL. the node you pass will not be
* searched, only the next one will; typically, you pass what the previous
* call returned.
* @type: The type string to match "device_type" or NULL to ignore
* @compatible: The string to match to one of the tokens in the device
* "compatible" list.
* @return node pointer or NULL if not found
*/
struct device_node *of_find_compatible_node(struct device_node *from,
const char *type, const char *compatible);

/**
* of_find_node_by_phandle() - Find a node given a phandle
*
* @handle: phandle of the node to find
*
* @return node pointer, or NULL if not found
*/
struct device_node *of_find_node_by_phandle(phandle handle);

/**
* of_read_u32() - Find and read a 32-bit integer from a property
*
* Search for a property in a device node and read a 32-bit value from
* it.
*
* @np: device node from which the property value is to be read.
* @propname: name of the property to be searched.
* @outp: pointer to return value, modified only if return value is 0.
*
* @return 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.
*/
int of_read_u32(const struct device_node *np, const char *propname, u32 *outp);

/**
* of_read_u32_array() - Find and read an array of 32 bit integers
*
* Search for a property in a device node and read 32-bit value(s) from
* it.
*
* @np: device node from which the property value is to be read.
* @propname: name of the property to be searched.
* @out_values: pointer to return value, modified only if return value is 0.
* @sz: number of array elements to read
* @return 0 on success, -EINVAL if the property does not exist, -ENODATA
* if property does not have a value, and -EOVERFLOW is longer than sz.
*/
int of_read_u32_array(const struct device_node *np, const char *propname,
u32 *out_values, size_t sz);

/**
* of_property_match_string() - Find string in a list and return index
*
* This function searches a string list property and returns the index
* of a specific string value.
*
* @np: pointer to node containing string list property
* @propname: string list property name
* @string: pointer to string to search for in string list
* @return 0 on success, -EINVAL if the property does not exist, -ENODATA
* if property does not have a value, and -EOVERFLOW is longer than sz.
*/
int of_property_match_string(const struct device_node *np, const char *propname,
const char *string);

int of_property_read_string_helper(const struct device_node *np,
const char *propname, const char **out_strs,
size_t sz, int index);

/**
* of_property_read_string_index() - Find and read a string from a multiple
* strings property.
* @np: device node from which the property value is to be read.
* @propname: name of the property to be searched.
* @index: index of the string in the list of strings
* @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) in the list of strings
* contained in that property.
* 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.
*/
static inline int of_property_read_string_index(const struct device_node *np,
const char *propname,
int index, const char **output)
{
int rc = of_property_read_string_helper(np, propname, output, 1, index);
return rc < 0 ? rc : 0;
}

/**
* 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
* @index: For properties holding a table of phandles, this is the index into
* the table
*
* Returns the device_node pointer with refcount incremented. Use
* of_node_put() on it when done.
*/
struct device_node *of_parse_phandle(const struct device_node *np,
const char *phandle_name, int index);

/**
* of_parse_phandle_with_args() - Find a node pointed by phandle in a list
*
* @np: pointer to a device tree node containing a list
* @list_name: property name that contains a list
* @cells_name: property name that specifies phandles' arguments count
* @index: index of a phandle to parse out
* @out_args: optional pointer to output arguments structure (will be filled)
* @return 0 on success (with @out_args filled out if not NULL), -ENOENT if
* @list_name does not exist, -EINVAL if a phandle was not found,
* @cells_name could not be found, the arguments were truncated or there
* were too many arguments.
*
* This function is useful to parse lists of phandles and their arguments.
* Returns 0 on success and fills out_args, on error returns appropriate
* errno value.
*
* Caller is responsible to call of_node_put() on the returned out_args->np
* pointer.
*
* Example:
*
* phandle1: node1 {
* #list-cells = <2>;
* }
*
* phandle2: node2 {
* #list-cells = <1>;
* }
*
* node3 {
* list = <&phandle1 1 2 &phandle2 3>;
* }
*
* To get a device_node of the `node2' node you may call this:
* of_parse_phandle_with_args(node3, "list", "#list-cells", 1, &args);
*/
int of_parse_phandle_with_args(const struct device_node *np,
const char *list_name, const char *cells_name,
int index, struct of_phandle_args *out_args);

/**
* of_alias_scan() - Scan all properties of the 'aliases' node
*
* The function scans all the properties of the 'aliases' node and populates
* the lookup table with the properties. It returns the number of alias
* properties found, or an error code in case of failure.
*
* @return 9 if OK, -ENOMEM if not enough memory
*/
int of_alias_scan(void);

/**
* of_alias_get_id - Get alias id for the given device_node
*
* Travels the lookup table to get the alias id for the given device_node and
* alias stem.
*
* @np: Pointer to the given device_node
* @stem: Alias stem of the given device_node
* @return alias ID, if found, else -ENODEV
*/
int of_alias_get_id(const struct device_node *np, const char *stem);

/**
* of_get_stdout() - Get node to use for stdout
*
* @return node referred to by stdout-path alias, or NULL if none
*/
struct device_node *of_get_stdout(void);

#endif