From: Thierry Reding <treding@xxxxxxxxxx>
The new fdt_generate_phandle() function can be used to generate a new,
unused phandle given a specific device tree blob. The implementation is
somewhat naive in that it simply walks the entire device tree to find
the highest phandle value and then returns a phandle value one higher
than that. A more clever implementation might try to find holes in the
current set of phandle values and fill them. But this implementation is
relatively simple and works reliably.
Also add a test that validates that phandles generated by this new API
are indeed unique.
Signed-off-by: Thierry Reding <treding@xxxxxxxxxx>
---
libfdt/fdt_ro.c | 28 ++++++++++++++++++++++++++++
libfdt/libfdt.h | 15 +++++++++++++++
libfdt/libfdt_env.h | 1 +
tests/get_phandle.c | 31 ++++++++++++++++++++++++++++++-
4 files changed, 74 insertions(+), 1 deletion(-)
diff --git a/libfdt/fdt_ro.c b/libfdt/fdt_ro.c
index eafc14282892..cfb8499ecbd0 100644
--- a/libfdt/fdt_ro.c
+++ b/libfdt/fdt_ro.c
@@ -170,6 +170,34 @@ uint32_t fdt_get_max_phandle(const void *fdt)
return 0;
}
+int fdt_generate_phandle(const void *fdt, uint32_t *phandle)
+{
+ uint32_t max = 0;
+ int offset = -1;
+
+ while (true) {
+ uint32_t value;
+
+ offset = fdt_next_node(fdt, offset, NULL);
+ if (offset < 0) {
+ if (offset == -FDT_ERR_NOTFOUND)
+ break;
+
+ return offset;
+ }
+
+ value = fdt_get_phandle(fdt, offset);
+
+ if (value > max)
+ max = value;
+ }
+
+ if (phandle)
+ *phandle = max + 1;
+
+ return 0;
+}
+
static const struct fdt_reserve_entry *fdt_mem_rsv(const void *fdt, int n)
{
int offset = n * sizeof(struct fdt_reserve_entry);
diff --git a/libfdt/libfdt.h b/libfdt/libfdt.h
index a470d1df6d2a..cfe7e5fe3efe 100644
--- a/libfdt/libfdt.h
+++ b/libfdt/libfdt.h
@@ -376,6 +376,21 @@ const char *fdt_string(const void *fdt, int stroffset);
*/
uint32_t fdt_get_max_phandle(const void *fdt);
+/**
+ * fdt_generate_phandle - return a new, unused phandle for a device tree blob
+ * @fdt: pointer to the device tree blob
+ * @phandle: return location for the new phandle
+ *
+ * Walks the device tree blob and looks for the highest phandle value. On
+ * success, the new, unused phandle value (one higher than the previously
+ * highest phandle value in the device tree blob) will be returned in the
+ * @phandle parameter.
+ *
+ * Returns:
+ * 0 on success or a negative error-code on failure
+ */
+int fdt_generate_phandle(const void *fdt, uint32_t *phandle);
+
/**
* fdt_num_mem_rsv - retrieve the number of memory reserve map entries
* @fdt: pointer to the device tree blob
diff --git a/libfdt/libfdt_env.h b/libfdt/libfdt_env.h
index eb2053845c9c..4d1cdfa58547 100644
--- a/libfdt/libfdt_env.h
+++ b/libfdt/libfdt_env.h
@@ -52,6 +52,7 @@
* EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
+#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
diff --git a/tests/get_phandle.c b/tests/get_phandle.c
index 22bd7b81b3f0..d87aee50b065 100644
--- a/tests/get_phandle.c
+++ b/tests/get_phandle.c
@@ -17,6 +17,7 @@
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
+#include <stdbool.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
@@ -42,10 +43,32 @@ static void check_phandle(void *fdt, const char *path, uint32_t checkhandle)
path, phandle, checkhandle);
}
+static void check_phandle_unique(const void *fdt, uint32_t checkhandle)
+{
+ uint32_t phandle;
+ int offset = -1;
+
+ while (true) {
+ offset = fdt_next_node(fdt, offset, NULL);
+ if (offset < 0) {
+ if (offset == -FDT_ERR_NOTFOUND)
+ break;
+
+ FAIL("error looking for phandle %#x", checkhandle);
+ }
+
+ phandle = fdt_get_phandle(fdt, offset);
+
+ if (phandle == checkhandle)
+ FAIL("generated phandle already exists");
+ }
+}
+
int main(int argc, char *argv[])
{
- uint32_t max;
+ uint32_t max, phandle;
void *fdt;
+ int err;
test_init(argc, argv);
fdt = load_blob_arg(argc, argv);
@@ -59,5 +82,11 @@ int main(int argc, char *argv[])
FAIL("fdt_get_max_phandle returned 0x%x instead of 0x%x\n",
max, PHANDLE_2);
+ err = fdt_generate_phandle(fdt, &phandle);
+ if (err < 0)
+ FAIL("failed to generate phandle: %d", err);
+
+ check_phandle_unique(fdt, phandle);
+
PASS();
}
--
2.21.0
