Regressions that cause a device to no longer be probed by a driver can have a big impact on the platform's functionality, and despite being relatively common there isn't currently any generic test to detect them. As an example, bootrr [1] does test for device probe, but it requires defining the expected probed devices for each platform.
Given that the Devicetree already provides a static description of devices on the system, it is a good basis for building such a test on top.
This series introduces a test to catch regressions that prevent devices from probing.
Patches 1 and 2 extend the existing dt-extract-compatibles to be able to output only the compatibles that can be expected to match a Devicetree node to a driver. Patch 2 adds a kselftest that walks over the Devicetree nodes on the current platform and compares the compatibles to the ones on the list, and on an ignore list, to point out devices that failed to be probed.
A compatible list is needed because not all compatibles that can show up in a Devicetree node can be used to match to a driver, for example the code for that compatible might use "OF_DECLARE" type macros and avoid the driver framework, or the node might be controlled by a driver that was bound to a different node.
An ignore list is needed for the few cases where it's common for a driver to match a device but not probe, like for the "simple-mfd" compatible, where the driver only probes if that compatible is the node's first compatible.
The reason for parsing the kernel source instead of relying on information exposed by the kernel at runtime (say, looking at modaliases or introducing some other mechanism), is to be able to catch issues where a config was renamed or a driver moved across configs, and the .config used by the kernel not updated accordingly. We need to parse the source to find all compatibles present in the kernel independent of the current config being run.
[1] https://github.com/kernelci/bootrr
Changes in v2: - Extended dt-extract-compatibles script to be able to extract driver matching compatibles, instead of adding a new one in Coccinelle - Made kselftest output in the KTAP format
Nícolas F. R. A. Prado (3): dt: dt-extract-compatibles: Handle cfile arguments in generator function dt: dt-extract-compatibles: Add flag for driver matching compatibles kselftest: Add new test for detecting unprobed Devicetree devices
scripts/dtc/dt-extract-compatibles | 74 +++++++++++++---- tools/testing/selftests/Makefile | 1 + tools/testing/selftests/dt/.gitignore | 1 + tools/testing/selftests/dt/Makefile | 21 +++++ .../selftests/dt/compatible_ignore_list | 1 + tools/testing/selftests/dt/ktap_helpers.sh | 57 +++++++++++++ .../selftests/dt/test_unprobed_devices.sh | 79 +++++++++++++++++++ 7 files changed, 218 insertions(+), 16 deletions(-) create mode 100644 tools/testing/selftests/dt/.gitignore create mode 100644 tools/testing/selftests/dt/Makefile create mode 100644 tools/testing/selftests/dt/compatible_ignore_list create mode 100644 tools/testing/selftests/dt/ktap_helpers.sh create mode 100755 tools/testing/selftests/dt/test_unprobed_devices.sh