[Linux-kernel-mentees] Linux kernel checkpatch.pl mentorship

Dwaipayan Ray dwaipayanray1 at gmail.com
Mon Sep 14 12:31:37 UTC 2020

On Mon, Sep 14, 2020 at 10:47 AM Lukas Bulwahn <lukas.bulwahn at gmail.com>
> On Mon, 14 Sep 2020, Dwaipayan Ray wrote:
> >
> >
> > > You should also try to find a case where checkpatch.pl can be
> > >
> > > - It is best if you look at the checkpatch.pl error/warning reports
> > > check if you can find a class of typical false positives in the
> > > data. Then, think about how to make the pattern in checkpatch and
> > > a patch to checkpatch.pl on this mailing list; with the evaluation
> > > backing that your patch really improves the situation. We will then
> > > and check your patch as well.
> > >
> > > - If you really cannot find a typical false positive, maybe you can
> > > the task from Ayush to fix checkpatch with git ranges?
> > >
> > Hi,I will try to find and evaluate the possibiltiy of such a case, and
report my finding
> > as soon as I find something substantial.
> >
> > I may also require some advice from you on the patch submission process.
> >
> That is what a mentor is there for, but try hard to understand the
> warnings yourself first. This is a mentorship, not a tutorial.
> Lukas

I looked into the checkpatch.pl 's output I collected. And I have found
some possible candidates
but I would like your opinion on them.

The first one is double warnings for the same kind of coding style error.
If an SPDX tag is in the following format: "// SPDX-License-Identifier:
then checkpatch.pl generates two warnings:

1) Improper SPDX comment style for ... , please use '/*' instead.
2) Missing or malformed SPDX-License-Identifier tag in line 1.

Example: commit 726721a51838
Warnings generated:

WARNING:SPDX_LICENSE_TAG: Improper SPDX comment style for
'kernel/trace/trace_synth.h', please use '/*' instead
#4041: FILE: kernel/trace/trace_synth.h:1:
+// SPDX-License-Identifier: GPL-2.0

WARNING:SPDX_LICENSE_TAG: Missing or malformed SPDX-License-Identifier tag
in line 1
#4041: FILE: kernel/trace/trace_synth.h:1:
+// SPDX-License-Identifier: GPL-2.0

In my opinion, only one warning should suffice if a '//' comment style is
used in spdx tag.
But I would like to know your view on it.

The second candidate is related to the following warning:

WARNING:SPDX_LICENSE_TAG: DT binding documents should be licensed
(GPL-2.0-only OR BSD-2-Clause)
#110: FILE:
+# SPDX-License-Identifier: GPL-2.0-only

In checkpath.pl line 3209:
 $fixed[$fixlinenr] =~ s/SPDX-License-Identifier:
.*/SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)/;

The desired fix is "(GPL-2.0-only OR BSD-2-Clause)" . Shouldn't the
identifier be "GPL-2.0-only"
or "BSD-2-Clause", that is either of them? Or was the former the decided

The third candidate is related to the warning:

WARNING:NO_AUTHOR_SIGN_OFF: Missing Signed-off-by: line by nominal patch
author ...

I found several such commits in which the author had used different mail
addresses in the
signed-off -by section, due to which this warning is generated.

An example is Commit dc5bdb68b5b3 .
Git log show:
Author: Daniel Vetter <daniel.vetter at ffwll.ch>
Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>

This is infact a common scenario. I easily found another commit
Git log shows:
Author: Minas Harutyunyan <Minas.Harutyunyan at synopsys.com>
Signed-off-by: Minas Harutyunyan <hminas at synopsys.com>

This warning could be avoided or at least handled better.

I would like to know if any of them can be worked on.

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