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libfdt: Add phandle generation helper

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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: <20190320151003.28941-1-thierry.reding@gmail.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
Thierry Reding
2019-03-20 16:10:03 +01:00
committed by David Gibson
parent 4762ad051e
commit 54ea41c224
9 changed files with 114 additions and 3 deletions
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31
tests/get_phandle.c
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@@ -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();
}