libfdt: Implement property iteration functions
David Gibson
david at gibson.dropbear.id.au
Tue Mar 9 17:39:14 EST 2010
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 at gibson.dropbear.id.au>
Index: dtc/libfdt/libfdt.h
===================================================================
--- dtc.orig/libfdt/libfdt.h 2010-03-01 14:21:49.188385823 +1100
+++ dtc/libfdt/libfdt.h 2010-03-09 17:35:36.582984236 +1100
@@ -343,6 +343,75 @@ int fdt_path_offset(const void *fdt, con
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
* @nodeoffset: offset of the node whose property to find
@@ -396,6 +465,40 @@ static inline struct fdt_property *fdt_g
}
/**
+ * 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
* @nodeoffset: offset of the node whose property to find
Index: dtc/libfdt/fdt_ro.c
===================================================================
--- dtc.orig/libfdt/fdt_ro.c 2010-03-09 10:48:19.867110161 +1100
+++ dtc/libfdt/fdt_ro.c 2010-03-09 15:49:40.791373387 +1100
@@ -105,6 +105,30 @@ 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)
{
@@ -194,52 +218,66 @@ const char *fdt_get_name(const void *fdt
return NULL;
}
-const struct fdt_property *fdt_get_property_namelen(const void *fdt,
- int nodeoffset,
- const char *name,
- int namelen, int *lenp)
+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)
{
- uint32_t tag;
- const struct fdt_property *prop;
- int offset, nextoffset;
int err;
+ const struct fdt_property *prop;
- if (((err = fdt_check_header(fdt)) != 0)
- || ((err = _fdt_check_node_offset(fdt, nodeoffset)) < 0))
- goto fail;
+ if ((err = _fdt_check_prop_offset(fdt, offset)) < 0) {
+ if (lenp)
+ *lenp = err;
+ return NULL;
+ }
- nextoffset = err;
- do {
- offset = nextoffset;
+ prop = _fdt_offset_ptr(fdt, offset);
- 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;
+ if (lenp)
+ *lenp = fdt32_to_cpu(prop->len);
- 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;
+}
- return prop;
- }
+const struct fdt_property *fdt_get_property_namelen(const void *fdt,
+ int offset,
+ const char *name,
+ int namelen, int *lenp)
+{
+ for (offset = fdt_first_property_offset(fdt, offset);
+ (offset >= 0);
+ (offset = fdt_next_property_offset(fdt, offset))) {
+ const struct fdt_property *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;
}
@@ -263,6 +301,19 @@ const void *fdt_getprop_namelen(const vo
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)
{
Index: dtc/libfdt/fdt.c
===================================================================
--- dtc.orig/libfdt/fdt.c 2010-03-09 10:48:19.835109791 +1100
+++ dtc/libfdt/fdt.c 2010-03-09 15:22:01.743164531 +1100
@@ -149,6 +149,15 @@ int _fdt_check_node_offset(const void *f
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;
Index: dtc/libfdt/libfdt_internal.h
===================================================================
--- dtc.orig/libfdt/libfdt_internal.h 2010-03-09 15:23:12.214109947 +1100
+++ dtc/libfdt/libfdt_internal.h 2010-03-09 15:23:16.351175258 +1100
@@ -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);
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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