Re: [RFC PATCH 0/2] Add a test to catch unprobed Devicetree devices

Rob Herring
2023-08-10T21:55:11Z

On Thu, Aug 10, 2023 at 03:43:09PM -0600, Rob Herring wrote:
> On Thu, Aug 10, 2023 at 04:23:49PM -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.
> >
> > Patch 1 introduces a script to parse the kernel source using Coccinelle
> > and extract all compatibles that can be matched by 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.
> >
> > Even though there's already scripts/dtc/dt-extract-compatibles that does
> > a similar job, it didn't seem to find all compatibles, returning ~3k,
> > while Coccinelle found ~11k. Besides that, Coccinelle actually parses
> > the C files, so it should be a more robust solution than relying on
> > regexes.
>
> I just sent a patch[1] last week fixing missing a bunch. I only looked
> at the change in count of undocumented (by schema) though.

With the existing script, I get 11761 compatibles and 12916 with my fix.
So how are you getting only 3k?

Rob