netdev - Re: [PATCH net-next v1 1/6] ethtool: add interface to read Tx hardware timestamping statistics

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Message-ID: <87wmpeyx70.fsf@nvidia.com>
Date: Wed, 03 Apr 2024 13:56:06 -0700
From: Rahul Rameshbabu <rrameshbabu@...dia.com>
To: "Keller, Jacob E" <jacob.e.keller@...el.com>
Cc: Jakub Kicinski <kuba@...nel.org>, "netdev@...r.kernel.org"
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Subject: Re: [PATCH net-next v1 1/6] ethtool: add interface to read Tx
 hardware timestamping statistics

On Wed, 03 Apr, 2024 18:44:52 +0000 "Keller, Jacob E" <jacob.e.keller@...el.com> wrote:
>> On Tue, 02 Apr, 2024 19:18:42 -0700 Jakub Kicinski <kuba@...nel.org> wrote:
>> > On Tue,  2 Apr 2024 13:52:01 -0700 Rahul Rameshbabu wrote:
>> >> +/**
>> >> + * struct ethtool_ts_stats - HW timestamping statistics
>> >> + * @tx_stats: struct group for TX HW timestamping
>> >> + *	@pkts: Number of packets successfully timestamped by the hardware.
>> >> + *	@lost: Number of hardware timestamping requests where the
>> timestamping
>> >> + *		information from the hardware never arrived for submission with
>> >> + *		the skb.
>> >> + *	@err: Number of arbitrary timestamp generation error events that the
>> >> + *		hardware encountered, exclusive of @lost statistics. Cases such
>> >> + *		as resource exhaustion, unavailability, firmware errors, and
>> >> + *		detected illogical timestamp values not submitted with the skb
>> >> + *		are inclusive to this counter.
>> >> + */
>> >> +struct ethtool_ts_stats {
>> >> +	struct_group(tx_stats,
>> >
>> > Doesn't seem like the group should be documented:
>> >
>> > include/linux/ethtool.h:503: warning: Excess struct member 'tx_stats'
>> description in 'ethtool_ts_stats'
>> 
>> Was looking into why our internal verification did not catch this. We
>> run W=1 with clang, but looks like the warning does not get triggered
>> unless explicitly run with scripts/kernel-doc.
>> 
>>   https://www.kernel.org/doc/html/latest/doc-guide/kernel-doc.html#how-to-
>> format-kernel-doc-comments
>> 
>> I have debugged using strace that the way the kernel doc checking works
>> when W=1 is set is that the matching source file that is being compiled
>> is passed to scripts/kernel-doc, so include files are missed from the
>> doc check. I think this is worth adding to the kernel documentation.
>> 
>
> It would be great if the W=1 setup could figure out the include files and send
> those to kernel-doc too, but I'm not sure if this is possible and if so how
> difficult it would be to implement it. A lot of headers produce warnings because
> a lot fewer people manually run kernel-doc on the entire source.
>

I took a look into this, and the one naive solution I had in mind was a
checkdocs target for the kernel where you use gcc -MM to deduce all the
includes, create a unique list, and then run scripts/kernel-doc against
the list of include files. That said, I do think this is excessive
compared to having a checkpatch logic that runs scripts/kernel-doc on
the parts that change in your commit before and after the patch is
applied.

Kudos to the netdev CI for having this.

  https://github.com/linux-netdev/nipa/blob/main/tests/patch/kdoc/kdoc.sh