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allow paths in fdt_path_offset to begin with a &label reference

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When using the CLI tools fdtget and fdtput, or other tools built on
top of libfdt (such as perhaps scripts written in Python), it can be
convenient to refer to a node by a label rather than having to know
the full path from the root.

Signed-off-by: Rasmus Villemoes <ravi@prevas.dk>
This commit is contained in:
Rasmus Villemoes 2024-10-07 16:05:16 +02:00
parent 617f3d9b60
commit 2675c5896a
2 changed files with 16 additions and 6 deletions
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6
libfdt/fdt_ro.c
View file

@ -258,14 +258,18 @@ int fdt_path_offset_namelen(const void *fdt, const char *path, int namelen)
if (!can_assume(VALID_INPUT) && namelen <= 0)
return -FDT_ERR_BADPATH;
/* see if we have an alias */
/* see if we have an alias or symbol */
if (*path != '/') {
const char *q = memchr(path, '/', end - p);
if (!q)
q = end;
if (*p == '&')
p = fdt_get_symbol_namelen(fdt, p + 1, q - p - 1);
else
p = fdt_get_alias_namelen(fdt, p, q - p);
if (!p)
return -FDT_ERR_BADPATH;
offset = fdt_path_offset(fdt, p);

14
libfdt/libfdt.h
View file

@ -570,9 +570,10 @@ int fdt_path_offset_namelen(const void *fdt, const char *path, int namelen);
* address).
*
* If the path is not absolute (i.e. does not begin with '/'), the
* first component is treated as an alias. That is, the property by
* that name is looked up in the /aliases node, and the value of that
* property used in place of that first component.
* first component is treated as an alias (or, if it begins with '&',
* the rest is treated as a symbol). That is, the property by that
* name is looked up in the /aliases (or /__symbols__) node, and the
* value of that property used in place of that first component.
*
* For example, for this small fragment
*
@ -592,12 +593,17 @@ int fdt_path_offset_namelen(const void *fdt, const char *path, int namelen);
*
* /soc@0/i2c@30a40000/eeprom@52
* i2c2/eeprom@52
* &foo/eeprom@52
* &bar
*
* The latter two only work if the device tree blob has been compiled
* with the -@ dtc option.
*
* returns:
* structure block offset of the node with the requested path (>=0), on
* success
* -FDT_ERR_BADPATH, given path does not begin with '/' and the first
* component is not a valid alias
* component is not a valid alias or symbol
* -FDT_ERR_NOTFOUND, if the requested node does not exist
* -FDT_ERR_BADMAGIC,
* -FDT_ERR_BADVERSION,