diff options
| author | Simon Glass | 2022-09-06 20:27:05 -0600 |
|---|---|---|
| committer | Tom Rini | 2022-09-29 16:09:56 -0400 |
| commit | 0e4b697f884d1f2190a9972b662abc8498159333 (patch) | |
| tree | 0d81dadb200fadc7a74a0d1cece914af244f4fa7 /doc | |
| parent | 98306987659769607642474954b2bf9555808542 (diff) | |
test: Make a copy of the device tree before running a test
When the flat device tree changes it can mess up the live tree since that
uses the flat tree for its strings. This affects only a few sandbox tests
which modify the device tree, but the number will grow as ofnode support
for writing improves.
While the control FDT is not intended to change while U-Boot is running,
some tests do so. For example, the ofnode interface only supports
modifying properties in the control FDT, so tests must use that.
To solve this problem, keep a copy of the FDT and restore it as needed
when the test is finished. The copy only happens on sandbox (except SPL
builds), to reduce memory usage and because these tests are not useful on
other boards. For other boards, a checksum is taken to ensure that nothing
changes.
It would be possible to always checksum the FDT on sandbox and only
restore it if needed, but this is slightly slower than restoring it every
time, at least with crc8.
Move the code which checks for success to the very end, for clarity.
Signed-off-by: Simon Glass <sjg@chromium.org>
Diffstat (limited to 'doc')
| -rw-r--r-- | doc/develop/driver-model/livetree.rst | 17 |
1 files changed, 3 insertions, 14 deletions
diff --git a/doc/develop/driver-model/livetree.rst b/doc/develop/driver-model/livetree.rst index faf3eb5b5f0..4ef8c517325 100644 --- a/doc/develop/driver-model/livetree.rst +++ b/doc/develop/driver-model/livetree.rst @@ -235,20 +235,9 @@ tree either present or absent. This is to make sure that the flat tree functions work correctly even with OF_LIVE is enabled. But if a test modifies the flat device tree, then the live tree can become invalid. Any live tree tests that run after that point will use a corrupted tree, e.g. with an incorrect property name -or worse. To deal with this we use a flag UT_TESTF_LIVE_OR_FLAT then ensures -that tests which write to the flat tree are not run if OF_LIVE is enabled. Only -the live tree version of the test is run, when OF_LIVE is enabled, with -sandbox_flattree running the flat tree version. - -This is of course a work-around, even if a reasonable one. One solution to this -problem would be to make a copy of the flat tree before the test and restore it -afterwards, in the same memory location, so that the live tree pointers work -again. Another would be to regenerate the live tree if a test modified the flat -tree. - -Neither of these solutions is currently implemented, since the situation that -causes the problem can only occur in sandbox tests, is somewhat esoteric and -the UT_TESTF_LIVE_OR_FLAT flag deals with it in a reasonable way. +or worse. To deal with this we take a copy of the device tree and restore it +after any test that modifies it. Note that this copy is not made on other +boards, only sandbox. Multiple livetrees |