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libfdt: Add fdt_next_subnode() to permit easy subnode iteration

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Iterating through subnodes with libfdt is a little painful to write as we
need something like this:

for (depth = 0, count = 0,
	offset = fdt_next_node(fdt, parent_offset, &depth);
     (offset >= 0) && (depth > 0);
     offset = fdt_next_node(fdt, offset, &depth)) {
	if (depth == 1) {
		/* code body */
	}
}

Using fdt_next_subnode() we can instead write this, which is shorter and
easier to get right:

for (offset = fdt_first_subnode(fdt, parent_offset);
     offset >= 0;
     offset = fdt_next_subnode(fdt, offset)) {
	/* code body */
}

Also, it doesn't require two levels of indentation for the loop body.

Signed-off-by: Simon Glass <sjg@chromium.org>
(Cherry-picked from dtc commit 4e76ec79)
Acked-by: Gerald Van Baren <vanbaren@cideas.com>
This commit is contained in:
Simon Glass 2013-05-07 06:11:50 +00:00 committed by Tom Rini
parent 816cb037ad
commit 88f95bbadd
2 changed files with 50 additions and 0 deletions
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22
include/libfdt.h
View File

@ -136,6 +136,28 @@ uint32_t fdt_next_tag(const void *fdt, int offset, int *nextoffset);
int fdt_next_node(const void *fdt, int offset, int *depth);
/**
* fdt_first_subnode() - get offset of first direct subnode
*
* @fdt: FDT blob
* @offset: Offset of node to check
* @return offset of first subnode, or -FDT_ERR_NOTFOUND if there is none
*/
int fdt_first_subnode(const void *fdt, int offset);
/**
* fdt_next_subnode() - get offset of next direct subnode
*
* After first calling fdt_first_subnode(), call this function repeatedly to
* get direct subnodes of a parent node.
*
* @fdt: FDT blob
* @offset: Offset of previous subnode
* @return offset of next subnode, or -FDT_ERR_NOTFOUND if there are no more
* subnodes
*/
int fdt_next_subnode(const void *fdt, int offset);
/**********************************************************************/
/* General functions */
/**********************************************************************/

28
lib/libfdt/fdt.c
View File

@ -202,6 +202,34 @@ int fdt_next_node(const void *fdt, int offset, int *depth)
return offset;
}
int fdt_first_subnode(const void *fdt, int offset)
{
int depth = 0;
offset = fdt_next_node(fdt, offset, &depth);
if (offset < 0 || depth != 1)
return -FDT_ERR_NOTFOUND;
return offset;
}
int fdt_next_subnode(const void *fdt, int offset)
{
int depth = 1;
/*
* With respect to the parent, the depth of the next subnode will be
* the same as the last.
*/
do {
offset = fdt_next_node(fdt, offset, &depth);
if (offset < 0 || depth < 1)
return -FDT_ERR_NOTFOUND;
} while (depth > 1);
return offset;
}
const char *_fdt_find_string(const char *strtab, int tabsize, const char *s)
{
int len = strlen(s) + 1;