path: root/cpukit/dtc
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authorThierry Reding <>2019-03-26 16:33:02 +0100
committerSebastian Huber <>2020-03-02 07:52:19 +0100
commit5a457750ec5b1916602da8f18565232916e9713e (patch)
treefcf2e1d19c37d768841192600144b232f466ba12 /cpukit/dtc
parentlibfdt: Add new maximum phandle lookup function (diff)
libfdt: Add phandle generation helper
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 <> Message-Id: <> Signed-off-by: David Gibson <>
Diffstat (limited to 'cpukit/dtc')
1 files changed, 18 insertions, 0 deletions
diff --git a/cpukit/dtc/libfdt/fdt_ro.c b/cpukit/dtc/libfdt/fdt_ro.c
index 1d0335ee71..817ac39099 100644
--- a/cpukit/dtc/libfdt/fdt_ro.c
+++ b/cpukit/dtc/libfdt/fdt_ro.c
@@ -184,6 +184,24 @@ uint32_t fdt_get_max_phandle(const void *fdt)
return phandle;
+int fdt_generate_phandle(const void *fdt, uint32_t *phandle)
+ uint32_t max;
+ int err;
+ err = fdt_find_max_phandle(fdt, &max);
+ if (err < 0)
+ return err;
+ if (max == FDT_MAX_PHANDLE)
+ 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);