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authorThierry Reding <treding@nvidia.com>2019-03-26 16:33:02 +0100
committerSebastian Huber <sebastian.huber@embedded-brains.de>2020-03-02 07:52:19 +0100
commit5a457750ec5b1916602da8f18565232916e9713e (patch)
treefcf2e1d19c37d768841192600144b232f466ba12
parent6505fe0edea8762955e3c8dc86801bb0679ba4f7 (diff)
downloadrtems-5a457750ec5b1916602da8f18565232916e9713e.tar.bz2
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 <treding@nvidia.com> Message-Id: <20190326153302.17109-3-thierry.reding@gmail.com> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
-rw-r--r--cpukit/dtc/libfdt/fdt_ro.c18
-rw-r--r--cpukit/include/libfdt.h19
2 files changed, 37 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)
+ return -FDT_ERR_NOPHANDLES;
+
+ 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/cpukit/include/libfdt.h b/cpukit/include/libfdt.h
index e1498c3c21..39ff6d5d25 100644
--- a/cpukit/include/libfdt.h
+++ b/cpukit/include/libfdt.h
@@ -140,6 +140,10 @@
#define FDT_ERR_MAX 17
+/* constants */
+#define FDT_MAX_PHANDLE 0xfffffffe
+ /* Valid values for phandles range from 1 to 2^32-2. */
+
/**********************************************************************/
/* Low-level functions (you probably don't need these) */
/**********************************************************************/
@@ -417,6 +421,21 @@ int fdt_find_max_phandle(const void *fdt, uint32_t *phandle);
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
*