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

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Message-ID: <368a1fc3-02d7-49f2-a881-f39259f8c186@notapiano>
Date:   Wed, 20 Sep 2023 17:00:56 -0400
From:   Nícolas F. R. A. Prado 
        <nfraprado@...labora.com>
To:     Rob Herring <robh@...nel.org>
Cc:     Frank Rowand <frowand.list@...il.com>,
        Shuah Khan <shuah@...nel.org>, 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 Wed, Sep 20, 2023 at 02:56:29PM -0500, Rob Herring wrote:
> On Wed, Sep 20, 2023 at 10:03:06AM -0400, Nícolas F. R. A. Prado wrote:
> > 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.
> 
> Sorry, now applied.
> 
> If you send something before or in the merge window, it is best to 
> rebase and resend after rc1 comes out.

Ah didn't know about that, will keep it in mind for the future, thanks!

Nícolas