From: Thierry Reding <treding@xxxxxxxxxx>
Given a device tree node, a property name and an index, the new function
fdt_stringlist_get() will return a pointer to the index'th string in the
property's value and return its length (or an error code on failure) in
an output argument.
Signed-off-by: Thierry Reding <treding@xxxxxxxxxx>
---
Changes in v3:
- rename function to fdt_stringlist_get()
- return string (or NULL) instead of string length (or error code)
- return length of string or error code in output parameter
- remove non-indexed shortcut
Changes in v2:
- handle non-NUL-terminated properties more gracefully
- improve documentation
libfdt/fdt_ro.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
libfdt/libfdt.h | 28 ++++++++++++++++++++++++++++
tests/strings.c | 32 ++++++++++++++++++++++++++++++++
3 files changed, 105 insertions(+)
diff --git a/libfdt/fdt_ro.c b/libfdt/fdt_ro.c
index dae31732148a..c56ed8e826fe 100644
--- a/libfdt/fdt_ro.c
+++ b/libfdt/fdt_ro.c
@@ -593,6 +593,51 @@ int fdt_stringlist_search(const void *fdt, int nodeoffset, const char *property,
return -FDT_ERR_NOTFOUND;
}
+const char *fdt_stringlist_get(const void *fdt, int nodeoffset,
+ const char *property, int index,
+ int *lenp)
+{
+ const char *list, *end;
+ int length;
+
+ list = fdt_getprop(fdt, nodeoffset, property, &length);
+ if (!list) {
+ if (lenp)
+ *lenp = length;
+
+ return NULL;
+ }
+
+ end = list + length;
+
+ while (list < end) {
+ length = strnlen(list, end - list) + 1;
+
+ /* Abort if the last string isn't properly NUL-terminated. */
+ if (list + length > end) {
+ if (lenp)
+ *lenp = -FDT_ERR_BADVALUE;
+
+ return NULL;
+ }
+
+ if (index == 0) {
+ if (lenp)
+ *lenp = length - 1;
+
+ return list;
+ }
+
+ list += length;
+ index--;
+ }
+
+ if (lenp)
+ *lenp = -FDT_ERR_NOTFOUND;
+
+ return NULL;
+}
+
int fdt_node_check_compatible(const void *fdt, int nodeoffset,
const char *compatible)
{
diff --git a/libfdt/libfdt.h b/libfdt/libfdt.h
index aa376b83e7e5..78adb1232e79 100644
--- a/libfdt/libfdt.h
+++ b/libfdt/libfdt.h
@@ -907,6 +907,34 @@ int fdt_stringlist_count(const void *fdt, int nodeoffset, const char *property);
int fdt_stringlist_search(const void *fdt, int nodeoffset, const char *property,
const char *string);
+/**
+ * fdt_stringlist_get() - obtain the string at a given index in a string list
+ * @fdt: pointer to the device tree blob
+ * @nodeoffset: offset of a tree node
+ * @property: name of the property containing the string list
+ * @index: index of the string to return
+ * @lenp: return location for the string length or an error code on failure
+ *
+ * Note that this will successfully extract strings from properties with
+ * non-NUL-terminated values. For example on small-valued cell properties
+ * this function will return the empty string.
+ *
+ * If non-NULL, the length of the string (on success) or a negative error-code
+ * (on failure) will be stored in the integer pointer to by lenp.
+ *
+ * @return:
+ * A pointer to the string at the given index in the string list or NULL on
+ * failure. On success the length of the string will be stored in the memory
+ * location pointed to by the lenp parameter, if non-NULL. On failure one of
+ * the following negative error codes will be returned in the lenp parameter
+ * (if non-NULL):
+ * -FDT_ERR_BADVALUE if the property value is not NUL-terminated
+ * -FDT_ERR_NOTFOUND if the property does not exist
+ */
+const char *fdt_stringlist_get(const void *fdt, int nodeoffset,
+ const char *property, int index,
+ int *lenp);
+
/**********************************************************************/
/* Read-only functions (addressing related) */
/**********************************************************************/
diff --git a/tests/strings.c b/tests/strings.c
index c8c7adb97051..8d23e965b58a 100644
--- a/tests/strings.c
+++ b/tests/strings.c
@@ -58,6 +58,13 @@ static void check_expected_failure(const void *fdt, const char *path,
err = fdt_stringlist_search(fdt, offset, "#address-cells", "");
if (err != 0)
FAIL("empty string not found in #address-cells: %d\n", err);
+
+ /*
+ * fdt_get_string() can successfully extract strings from non-string
+ * properties. This is because it doesn't necessarily parse the whole
+ * property value, which would be necessary for it to determine if a
+ * valid string or string list is present.
+ */
}
static void check_string_count(const void *fdt, const char *path,
@@ -96,6 +103,27 @@ static void check_string_index(const void *fdt, const char *path,
string, property, path, err, index);
}
+static void check_string(const void *fdt, const char *path,
+ const char *property, int index,
+ const char *string)
+{
+ const char *result;
+ int offset, len;
+
+ offset = fdt_path_offset(fdt, path);
+ if (offset < 0)
+ FAIL("Couldn't find path %s", path);
+
+ result = fdt_stringlist_get(fdt, offset, property, index, &len);
+ if (!result)
+ FAIL("Couldn't extract string %d from property %s of node %s: %d\n",
+ index, property, path, len);
+
+ if (strcmp(string, result) != 0)
+ FAIL("String %d in property %s of node %s is %s, expected %s\n",
+ index, property, path, result, string);
+}
+
int main(int argc, char *argv[])
{
void *fdt;
@@ -118,5 +146,9 @@ int main(int argc, char *argv[])
check_string_index(fdt, "/device", "compatible", "bar", 1);
check_string_index(fdt, "/device", "big-endian", "baz", -1);
+ check_string(fdt, "/", "compatible", 0, "test-strings");
+ check_string(fdt, "/device", "compatible", 0, "foo");
+ check_string(fdt, "/device", "compatible", 1, "bar");
+
PASS();
}
--
2.5.0
--
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