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libfdt: Implement property iteration functions 

For ages, we've been talking about adding functions to libfdt to allow
iteration through properties.  So, finally, here are some.

I got bogged down on this for a long time because I didn't want to
expose offsets directly to properties to the callers.  But without
that, attempting to make reasonable iteration functions just became
horrible.  So eventually, I settled on an interface which does now
expose property offsets.  fdt_first_property_offset() and
fdt_next_property_offset() are used to step through the offsets of the
properties starting from a particularly node offset.  The details of
the property at each offset can then be retrieved with either
fdt_get_property_by_offset() or fdt_getprop_by_offset() which have
interfaces similar to fdt_get_property() and fdt_getprop()
respectively.

No explicit testcases are included, but we do use the new functions to
reimplement the existing fdt_get_property() function.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

This was extracted from the DTC commit:
73dca9ae0b9abe6924ba640164ecce9f8df69c5a Mon Sep 17 00:00:00 2001

Signed-off-by: Gerald Van Baren <vanbaren@cideas.com>
This commit is contained in:
David Gibson 2010-03-09 17:39:14 +11:00 committed by Gerald Van Baren
parent 05a22ba096
commit d1c6314887
4 changed files with 201 additions and 37 deletions
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103
include/libfdt.h
View File

@ -342,6 +342,75 @@ int fdt_path_offset(const void *fdt, const char *path);
*/
const char *fdt_get_name(const void *fdt, int nodeoffset, int *lenp);
/**
* fdt_first_property_offset - find the offset of a node's first property
* @fdt: pointer to the device tree blob
* @nodeoffset: structure block offset of a node
*
* fdt_first_property_offset() finds the first property of the node at
* the given structure block offset.
*
* returns:
* structure block offset of the property (>=0), on success
* -FDT_ERR_NOTFOUND, if the requested node has no properties
* -FDT_ERR_BADOFFSET, if nodeoffset did not point to an FDT_BEGIN_NODE tag
* -FDT_ERR_BADMAGIC,
* -FDT_ERR_BADVERSION,
* -FDT_ERR_BADSTATE,
* -FDT_ERR_BADSTRUCTURE,
* -FDT_ERR_TRUNCATED, standard meanings.
*/
int fdt_first_property_offset(const void *fdt, int nodeoffset);
/**
* fdt_next_property_offset - step through a node's properties
* @fdt: pointer to the device tree blob
* @offset: structure block offset of a property
*
* fdt_next_property_offset() finds the property immediately after the
* one at the given structure block offset. This will be a property
* of the same node as the given property.
*
* returns:
* structure block offset of the next property (>=0), on success
* -FDT_ERR_NOTFOUND, if the given property is the last in its node
* -FDT_ERR_BADOFFSET, if nodeoffset did not point to an FDT_PROP tag
* -FDT_ERR_BADMAGIC,
* -FDT_ERR_BADVERSION,
* -FDT_ERR_BADSTATE,
* -FDT_ERR_BADSTRUCTURE,
* -FDT_ERR_TRUNCATED, standard meanings.
*/
int fdt_next_property_offset(const void *fdt, int offset);
/**
* fdt_get_property_by_offset - retrieve the property at a given offset
* @fdt: pointer to the device tree blob
* @offset: offset of the property to retrieve
* @lenp: pointer to an integer variable (will be overwritten) or NULL
*
* fdt_get_property_by_offset() retrieves a pointer to the
* fdt_property structure within the device tree blob at the given
* offset. If lenp is non-NULL, the length of the property value is
* also returned, in the integer pointed to by lenp.
*
* returns:
* pointer to the structure representing the property
* if lenp is non-NULL, *lenp contains the length of the property
* value (>=0)
* NULL, on error
* if lenp is non-NULL, *lenp contains an error code (<0):
* -FDT_ERR_BADOFFSET, nodeoffset did not point to FDT_PROP tag
* -FDT_ERR_BADMAGIC,
* -FDT_ERR_BADVERSION,
* -FDT_ERR_BADSTATE,
* -FDT_ERR_BADSTRUCTURE,
* -FDT_ERR_TRUNCATED, standard meanings
*/
const struct fdt_property *fdt_get_property_by_offset(const void *fdt,
int offset,
int *lenp);
/**
* fdt_get_property_namelen - find a property based on substring
* @fdt: pointer to the device tree blob
@ -395,6 +464,40 @@ static inline struct fdt_property *fdt_get_property_w(void *fdt, int nodeoffset,
fdt_get_property(fdt, nodeoffset, name, lenp);
}
/**
* fdt_getprop_by_offset - retrieve the value of a property at a given offset
* @fdt: pointer to the device tree blob
* @ffset: offset of the property to read
* @namep: pointer to a string variable (will be overwritten) or NULL
* @lenp: pointer to an integer variable (will be overwritten) or NULL
*
* fdt_getprop_by_offset() retrieves a pointer to the value of the
* property at structure block offset 'offset' (this will be a pointer
* to within the device blob itself, not a copy of the value). If
* lenp is non-NULL, the length of the property value is also
* returned, in the integer pointed to by lenp. If namep is non-NULL,
* the property's namne will also be returned in the char * pointed to
* by namep (this will be a pointer to within the device tree's string
* block, not a new copy of the name).
*
* returns:
* pointer to the property's value
* if lenp is non-NULL, *lenp contains the length of the property
* value (>=0)
* if namep is non-NULL *namep contiains a pointer to the property
* name.
* NULL, on error
* if lenp is non-NULL, *lenp contains an error code (<0):
* -FDT_ERR_BADOFFSET, nodeoffset did not point to FDT_PROP tag
* -FDT_ERR_BADMAGIC,
* -FDT_ERR_BADVERSION,
* -FDT_ERR_BADSTATE,
* -FDT_ERR_BADSTRUCTURE,
* -FDT_ERR_TRUNCATED, standard meanings
*/
const void *fdt_getprop_by_offset(const void *fdt, int offset,
const char **namep, int *lenp);
/**
* fdt_getprop_namelen - get property value based on substring
* @fdt: pointer to the device tree blob

9
lib/libfdt/fdt.c
View File

@ -153,6 +153,15 @@ int _fdt_check_node_offset(const void *fdt, int offset)
return offset;
}
int _fdt_check_prop_offset(const void *fdt, int offset)
{
if ((offset < 0) || (offset % FDT_TAGSIZE)
|| (fdt_next_tag(fdt, offset, &offset) != FDT_PROP))
return -FDT_ERR_BADOFFSET;
return offset;
}
int fdt_next_node(const void *fdt, int offset, int *depth)
{
int nextoffset = 0;

125
lib/libfdt/fdt_ro.c
View File

@ -109,6 +109,30 @@ int fdt_num_mem_rsv(const void *fdt)
return i;
}
static int _nextprop(const void *fdt, int offset)
{
uint32_t tag;
int nextoffset;
do {
tag = fdt_next_tag(fdt, offset, &nextoffset);
switch (tag) {
case FDT_END:
if (nextoffset >= 0)
return -FDT_ERR_BADSTRUCTURE;
else
return nextoffset;
case FDT_PROP:
return offset;
}
offset = nextoffset;
} while (tag == FDT_NOP);
return -FDT_ERR_NOTFOUND;
}
int fdt_subnode_offset_namelen(const void *fdt, int offset,
const char *name, int namelen)
{
@ -198,52 +222,66 @@ const char *fdt_get_name(const void *fdt, int nodeoffset, int *len)
return NULL;
}
int fdt_first_property_offset(const void *fdt, int nodeoffset)
{
int offset;
if ((offset = _fdt_check_node_offset(fdt, nodeoffset)) < 0)
return offset;
return _nextprop(fdt, offset);
}
int fdt_next_property_offset(const void *fdt, int offset)
{
if ((offset = _fdt_check_prop_offset(fdt, offset)) < 0)
return offset;
return _nextprop(fdt, offset);
}
const struct fdt_property *fdt_get_property_by_offset(const void *fdt,
int offset,
int *lenp)
{
int err;
const struct fdt_property *prop;
if ((err = _fdt_check_prop_offset(fdt, offset)) < 0) {
if (lenp)
*lenp = err;
return NULL;
}
prop = _fdt_offset_ptr(fdt, offset);
if (lenp)
*lenp = fdt32_to_cpu(prop->len);
return prop;
}
const struct fdt_property *fdt_get_property_namelen(const void *fdt,
int nodeoffset,
int offset,
const char *name,
int namelen, int *lenp)
{
uint32_t tag;
const struct fdt_property *prop;
int offset, nextoffset;
int err;
for (offset = fdt_first_property_offset(fdt, offset);
(offset >= 0);
(offset = fdt_next_property_offset(fdt, offset))) {
const struct fdt_property *prop;
if (((err = fdt_check_header(fdt)) != 0)
|| ((err = _fdt_check_node_offset(fdt, nodeoffset)) < 0))
goto fail;
nextoffset = err;
do {
offset = nextoffset;
tag = fdt_next_tag(fdt, offset, &nextoffset);
switch (tag) {
case FDT_END:
if (nextoffset < 0)
err = nextoffset;
else
/* FDT_END tag with unclosed nodes */
err = -FDT_ERR_BADSTRUCTURE;
goto fail;
case FDT_PROP:
prop = _fdt_offset_ptr(fdt, offset);
if (_fdt_string_eq(fdt, fdt32_to_cpu(prop->nameoff),
name, namelen)) {
/* Found it! */
if (lenp)
*lenp = fdt32_to_cpu(prop->len);
return prop;
}
if (!(prop = fdt_get_property_by_offset(fdt, offset, lenp))) {
offset = -FDT_ERR_INTERNAL;
break;
}
} while ((tag != FDT_BEGIN_NODE) && (tag != FDT_END_NODE));
if (_fdt_string_eq(fdt, fdt32_to_cpu(prop->nameoff),
name, namelen))
return prop;
}
err = -FDT_ERR_NOTFOUND;
fail:
if (lenp)
*lenp = err;
*lenp = offset;
return NULL;
}
@ -267,6 +305,19 @@ const void *fdt_getprop_namelen(const void *fdt, int nodeoffset,
return prop->data;
}
const void *fdt_getprop_by_offset(const void *fdt, int offset,
const char **namep, int *lenp)
{
const struct fdt_property *prop;
prop = fdt_get_property_by_offset(fdt, offset, lenp);
if (!prop)
return NULL;
if (namep)
*namep = fdt_string(fdt, fdt32_to_cpu(prop->nameoff));
return prop->data;
}
const void *fdt_getprop(const void *fdt, int nodeoffset,
const char *name, int *lenp)
{

1
lib/libfdt/libfdt_internal.h
View File

@ -63,6 +63,7 @@
}
int _fdt_check_node_offset(const void *fdt, int offset);
int _fdt_check_prop_offset(const void *fdt, int offset);
const char *_fdt_find_string(const char *strtab, int tabsize, const char *s);
int _fdt_node_end_offset(void *fdt, int nodeoffset);