From: Thierry Reding <treding@xxxxxxxxxx>
Given a device tree node and a property name, the new fdt_find_string()
function will look up a given string in the string list contained in the
property's value and return its index.
Signed-off-by: Thierry Reding <treding@xxxxxxxxxx>
---
Changes in v2:
- handle non-NUL-terminated properties more gracefully
- improve documentation
libfdt/fdt_ro.c | 30 ++++++++++++++++++++++++++++++
libfdt/libfdt.h | 22 ++++++++++++++++++++++
tests/strings.c | 40 ++++++++++++++++++++++++++++++++++++++++
3 files changed, 92 insertions(+)
diff --git a/libfdt/fdt_ro.c b/libfdt/fdt_ro.c
index cf55c71df79c..39b84b1cea60 100644
--- a/libfdt/fdt_ro.c
+++ b/libfdt/fdt_ro.c
@@ -563,6 +563,36 @@ int fdt_count_strings(const void *fdt, int nodeoffset, const char *property)
return count;
}
+int fdt_find_string(const void *fdt, int nodeoffset, const char *property,
+ const char *string)
+{
+ int length, len, index = 0;
+ const char *list, *end;
+
+ list = fdt_getprop(fdt, nodeoffset, property, &length);
+ if (!list)
+ return -length;
+
+ len = strlen(string) + 1;
+ 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)
+ return -FDT_ERR_BADVALUE;
+
+ if (length == len && memcmp(list, string, length) == 0)
+ return index;
+
+ list += length;
+ index++;
+ }
+
+ return -FDT_ERR_NOTFOUND;
+}
+
int fdt_node_check_compatible(const void *fdt, int nodeoffset,
const char *compatible)
{
diff --git a/libfdt/libfdt.h b/libfdt/libfdt.h
index bf60c1593e4e..e64680dd741c 100644
--- a/libfdt/libfdt.h
+++ b/libfdt/libfdt.h
@@ -885,6 +885,28 @@ int fdt_stringlist_contains(const char *strlist, int listlen, const char *str);
*/
int fdt_count_strings(const void *fdt, int nodeoffset, const char *property);
+/**
+ * fdt_find_string - find a string in a string list and return its index
+ * @fdt: pointer to the device tree blob
+ * @nodeoffset: offset of a tree node
+ * @property: name of the property containing the string list
+ * @string: string to look up in the string list
+ *
+ * Note that it is possible for this function to succeed on property values
+ * that are not NUL-terminated. That's because the function will stop after
+ * finding the first occurrence of @string. This can for example happen with
+ * small-valued cell properties, such as #address-cells, when searching for
+ * the empty string.
+ *
+ * @return:
+ * the index of the string in the list of strings
+ * -FDT_ERR_BADVALUE if the property value is not NUL-terminated
+ * -FDT_ERR_NOTFOUND if the property does not exist or does not contain
+ * the given string
+ */
+int fdt_find_string(const void *fdt, int nodeoffset, const char *property,
+ const char *string);
+
/**********************************************************************/
/* Read-only functions (addressing related) */
/**********************************************************************/
diff --git a/tests/strings.c b/tests/strings.c
index e10d9ece5a3e..29c49bfcc78c 100644
--- a/tests/strings.c
+++ b/tests/strings.c
@@ -40,6 +40,24 @@ static void check_expected_failure(const void *fdt, const char *path,
err = fdt_count_strings(fdt, offset, "#address-cells");
if (err != -FDT_ERR_BADVALUE)
FAIL("unexpectedly succeeded in parsing #address-cells\n");
+
+ err = fdt_find_string(fdt, offset, "#address-cells", "foo");
+ if (err != -FDT_ERR_BADVALUE)
+ FAIL("found string in #address-cells: %d\n", err);
+
+ /*
+ * Note that the #address-cells property contains a small 32-bit
+ * unsigned integer, hence some bytes will be zero, and searching for
+ * the empty string will succeed.
+ *
+ * The reason for this oddity is that the function will exit when the
+ * first occurrence of the string is found, but in order to determine
+ * that the property does not contain a valid string list it would
+ * need to process the whole value.
+ */
+ err = fdt_find_string(fdt, offset, "#address-cells", "");
+ if (err != 0)
+ FAIL("empty string not found in #address-cells: %d\n", err);
}
static void check_string_count(const void *fdt, const char *path,
@@ -61,6 +79,23 @@ static void check_string_count(const void *fdt, const char *path,
path, property, err, count);
}
+static void check_string_index(const void *fdt, const char *path,
+ const char *property, const char *string,
+ int index)
+{
+ int offset, err;
+
+ offset = fdt_path_offset(fdt, path);
+ if (offset < 0)
+ FAIL("Couldn't find path %s", path);
+
+ err = fdt_find_string(fdt, offset, property, string);
+
+ if (err != index)
+ FAIL("Index of %s in property %s of node %s is %d, expected %d\n",
+ string, property, path, err, index);
+}
+
int main(int argc, char *argv[])
{
void *fdt;
@@ -78,5 +113,10 @@ int main(int argc, char *argv[])
check_string_count(fdt, "/device", "compatible", 2);
check_string_count(fdt, "/device", "big-endian", 0);
+ check_string_index(fdt, "/", "compatible", "test-strings", 0);
+ check_string_index(fdt, "/device", "compatible", "foo", 0);
+ check_string_index(fdt, "/device", "compatible", "bar", 1);
+ check_string_index(fdt, "/device", "big-endian", "baz", -1);
+
PASS();
}
--
2.4.5
--
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