Re: [PATCH] docs: kdoc: fix duplicate section warning message

[Jacob Keller]

On 10/29/2025 12:45 PM, Randy Dunlap wrote:
> Hi Jacob,
> 
> On 10/29/25 11:30 AM, Jacob Keller wrote:
>> The python version of the kernel-doc parser emits some strange warnings
>> with just a line number in certain cases:
>>
>> $ ./scripts/kernel-doc -Wall -none 'include/linux/virtio_config.h'
>> Warning: 174
>> Warning: 184
>> Warning: 190
>> Warning: include/linux/virtio_config.h:226 No description found for return value of '__virtio_test_bit'
>> Warning: include/linux/virtio_config.h:259 No description found for return value of 'virtio_has_feature'
>> Warning: include/linux/virtio_config.h:283 No description found for return value of 'virtio_has_dma_quirk'
>> Warning: include/linux/virtio_config.h:392 No description found for return value of 'virtqueue_set_affinity'
>>
>> I eventually tracked this down to the lone call of emit_msg() in the
>> KernelEntry class, which looks like:
>>
>>   self.emit_msg(self.new_start_line, f"duplicate section name '{name}'\n")
>>
>> This looks like all the other emit_msg calls. Unfortunately, the definition
>> within the KernelEntry class takes only a message parameter and not a line
>> number. The intended message is passed as the warning!
>>
>> Pass the filename to the KernelEntry class, and use this to build the log
>> message in the same way as the KernelDoc class does.
>>
>> To avoid future errors, mark the warning parameter for both emit_msg
>> definitions as a keyword-only argument. This will prevent accidentally
>> passing a string as the warning parameter in the future.
>>
>> Also fix the call in dump_section to avoid an unnecessary additional
>> newline.
>>
>> Fixes: e3b42e94cf10 ("scripts/lib/kdoc/kdoc_parser.py: move kernel entry to a class")
>> Signed-off-by: Jacob Keller <jacob.e.keller@xxxxxxxxx>
>> ---
>> We recently discovered this while working on some netdev text
>> infrastructure. All of the duplicate section warnings are not being logged
>> properly, which was confusing the warning comparison logic we have for
>> testing patches in NIPA.
>>
>> This appears to have been caused by the optimizations in:
>> https://lore.kernel.org/all/cover.1745564565.git.mchehab+huawei@xxxxxxxxxx/
>>
>> Before this fix:
>> $ ./scripts/kernel-doc -Wall -none 'include/linux/virtio_config.h'
>> Warning: 174
>> Warning: 184
>> Warning: 190
>> Warning: include/linux/virtio_config.h:226 No description found for return value of '__virtio_test_bit'
>> Warning: include/linux/virtio_config.h:259 No description found for return value of 'virtio_has_feature'
>> Warning: include/linux/virtio_config.h:283 No description found for return value of 'virtio_has_dma_quirk'
>> Warning: include/linux/virtio_config.h:392 No description found for return value of 'virtqueue_set_affinity'
>>
>> After this fix:
>> $ ./scripts/kernel-doc -Wall -none 'include/linux/virtio_config.h'
>> Warning: include/linux/virtio_config.h:174 duplicate section name 'Return'
>> Warning: include/linux/virtio_config.h:184 duplicate section name 'Return'
>> Warning: include/linux/virtio_config.h:190 duplicate section name 'Return'
>> Warning: include/linux/virtio_config.h:226 No description found for return value of '__virtio_test_bit'
>> Warning: include/linux/virtio_config.h:259 No description found for return value of 'virtio_has_feature'
>> Warning: include/linux/virtio_config.h:283 No description found for return value of 'virtio_has_dma_quirk'
>> Warning: include/linux/virtio_config.h:392 No description found for return value of 'virtqueue_set_affinity'
>> ---
>>  scripts/lib/kdoc/kdoc_parser.py | 20 ++++++++++++--------
>>  1 file changed, 12 insertions(+), 8 deletions(-)
>>
> 
>> ---
>> base-commit: e53642b87a4f4b03a8d7e5f8507fc3cd0c595ea6
>> change-id: 20251029-jk-fix-kernel-doc-duplicate-return-warning-bd57ea39c628
> 
> What is that base-commit? I don't have it.
> It doesn't apply to linux-next (I didn't check docs-next).
> It does apply cleanly to kernel v6.18-rc3.
> 

Hm. Its e53642b87a4f ("Merge tag 'v6.18-rc3-smb-server-fixes' of
git://git.samba.org/ksmbd") which was the top of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git as of
when I made the commit. I wasn't sure which tree to base on since I'm
not a regular contributor to the docs stuff, so I just based on Linus's
tree instead of linux-next.

> and it does fix the Warning messages to be something useful. Thanks.
> 
> We'll have to see if Mauro already has a fix for this. (I reported
> it a couple of weeks ago.)

I searched mail archives but didn't find a report, so hence the patch.
If this already has a proper fix thats fine.

> If not, then this will need to apply to docs-next AFAIK.
>  

Ok, I can rebase if it is necessary. I'll check that out, and can send a
v2 if Mauro hasn't already fixed it somehow else.

> And not a problem with this patch, but those Returns: lines for
> each callback function shouldn't be there as Returns:. This is a
> struct declaration, not a function (or macro) declaration/definition.
> 

Yep, thats an issue with the header. They're doing something weird by
doing some sort of sub-documentation for each method of an ops struct. I
don't really know what the best fix is for this doc file, nor do I
particularly care. I just used it as an example because its the one that
we ran into while looking at output from the netdev testing infrastructure.

> Thanks.

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