linux-kernel - Re: [PATCH v3 0/3] Add a test to catch unprobed Devicetree devices

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Message-ID: <97c368a1-9c76-490a-848e-eacd6411e810@notapiano>
Date:   Wed, 20 Sep 2023 10:03:06 -0400
From:   Nícolas F. R. A. Prado 
        <nfraprado@...labora.com>
To:     Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Shuah Khan <shuah@...nel.org>
Cc:     Mark Brown <broonie@...nel.org>, kernelci@...ts.linux.dev,
        kernel@...labora.com, Guenter Roeck <groeck@...omium.org>,
        Bjorn Andersson <andersson@...nel.org>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v3 0/3] Add a test to catch unprobed Devicetree devices

On Mon, Aug 28, 2023 at 05:13:09PM -0400, Nícolas F. R. A. Prado wrote:
> 
> 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 v3:
> - Added DT selftest path to MAINTAINERS
> - Enabled device probe test for nodes with 'status = "ok"'
> - Added pass/fail/skip totals to end of test output
> 
> 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
> 
>  MAINTAINERS                                   |  1 +
>  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    | 70 ++++++++++++++++
>  .../selftests/dt/test_unprobed_devices.sh     | 83 +++++++++++++++++++
>  8 files changed, 236 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

Hi Rob,

gentle ping on this series.

I take it you'll be merging this through your tree, so I've added Shuah's R-b
that she supplied on v2 for the kselftest patch.

Thanks,
Nícolas