From: Thierry Reding <treding@xxxxxxxxxx>
Given a device tree node, a property name and an index, the new function
fdt_get_string_index() will return in an output argument a pointer to
the index'th string in the property's value.
The fdt_get_string() is a shortcut for the above with the index being 0.
Signed-off-by: Thierry Reding <treding@xxxxxxxxxx>
---
Changes in v2:
- handle non-NUL-terminated properties more gracefully
- improve documentation
libfdt/fdt_ro.c | 37 +++++++++++++++++++++++++++++++++++++
libfdt/libfdt.h | 41 +++++++++++++++++++++++++++++++++++++++++
tests/strings.c | 32 ++++++++++++++++++++++++++++++++
3 files changed, 110 insertions(+)
diff --git a/libfdt/fdt_ro.c b/libfdt/fdt_ro.c
index 39b84b1cea60..4315815969b6 100644
--- a/libfdt/fdt_ro.c
+++ b/libfdt/fdt_ro.c
@@ -593,6 +593,43 @@ int fdt_find_string(const void *fdt, int nodeoffset, const char *property,
return -FDT_ERR_NOTFOUND;
}
+int fdt_get_string_index(const void *fdt, int nodeoffset, const char *property,
+ int index, const char **output)
+{
+ const char *list, *end;
+ int length;
+
+ list = fdt_getprop(fdt, nodeoffset, property, &length);
+ if (!list)
+ return -length;
+
+ 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 (index == 0) {
+ *output = list;
+ return 0;
+ }
+
+ list += length;
+ index--;
+ }
+
+ return -FDT_ERR_NOTFOUND;
+}
+
+int fdt_get_string(const void *fdt, int nodeoffset, const char *property,
+ const char **output)
+{
+ return fdt_get_string_index(fdt, nodeoffset, property, 0, output);
+}
+
int fdt_node_check_compatible(const void *fdt, int nodeoffset,
const char *compatible)
{
diff --git a/libfdt/libfdt.h b/libfdt/libfdt.h
index e64680dd741c..bfbc8f9ead34 100644
--- a/libfdt/libfdt.h
+++ b/libfdt/libfdt.h
@@ -907,6 +907,47 @@ int fdt_count_strings(const void *fdt, int nodeoffset, const char *property);
int fdt_find_string(const void *fdt, int nodeoffset, const char *property,
const char *string);
+/**
+ * fdt_get_string_index() - 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
+ * @output: return location for the string
+ *
+ * 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.
+ *
+ * The @output parameter is only valid if the function returns 0.
+ *
+ * @return:
+ * 0 if the string was found (@output points to the string)
+ * -FDT_ERR_BADVALUE if the property value is not NUL-terminated
+ * -FDT_ERR_NOTFOUND if the property does not exist
+ */
+int fdt_get_string_index(const void *fdt, int nodeoffset, const char *property,
+ int index, const char **output);
+
+/**
+ * fdt_get_string() - obtain the first string 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
+ * @output: return location for the string
+ *
+ * This is a shorthand for:
+ *
+ * fdt_get_string_index(fdt, node, property, 0, output).
+ *
+ * @return:
+ * 0 if the string was found (@output points to the string)
+ * -FDT_ERR_BADVALUE if the property value is not NUL-terminated
+ * -FDT_ERR_NOTFOUND if the property does not exist
+ */
+int fdt_get_string(const void *fdt, int nodeoffset, const char *property,
+ const char **output);
+
/**********************************************************************/
/* Read-only functions (addressing related) */
/**********************************************************************/
diff --git a/tests/strings.c b/tests/strings.c
index 29c49bfcc78c..aa83ef0511be 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_find_string(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, err;
+
+ offset = fdt_path_offset(fdt, path);
+ if (offset < 0)
+ FAIL("Couldn't find path %s", path);
+
+ err = fdt_get_string_index(fdt, offset, property, index, &result);
+ if (err < 0)
+ FAIL("Couldn't extract string %d from property %s of node %s: %d\n",
+ index, property, path, err);
+
+ 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();
}
--
2.4.5
--
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