Re: [PATCH v3 5/5] io_uring/netcmd: add tx timestamping cmd support

[Jens Axboe <axboe@kernel.dk>]

On 6/12/25 8:26 AM, Pavel Begunkov wrote:
>>> diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
>>> index cfd17e382082..5c89e6f6d624 100644
>>> --- a/include/uapi/linux/io_uring.h
>>> +++ b/include/uapi/linux/io_uring.h
>>> @@ -968,6 +968,15 @@ enum io_uring_socket_op {
>>>       SOCKET_URING_OP_SIOCOUTQ,
>>>       SOCKET_URING_OP_GETSOCKOPT,
>>>       SOCKET_URING_OP_SETSOCKOPT,
>>> +    SOCKET_URING_OP_TX_TIMESTAMP,
>>> +};
>>> +
>>> +#define IORING_CQE_F_TIMESTAMP_HW    ((__u32)1 << IORING_CQE_BUFFER_SHIFT)
>>> +#define IORING_TIMESTAMP_TSTYPE_SHIFT    (IORING_CQE_BUFFER_SHIFT + 1)
>>
>> Don't completely follow this, would at the very least need a comment.
>> Whether it's a HW or SW timestamp is flagged in the upper 16 bits, just
>> like a provided buffer ID. But since we don't use buffer IDs here, then
>> it's up for grabs. Do we have other commands that use the upper flags
>> space for command private flags?
> 
> Probably not, but the place is better than the lower half, which
> has common flags like F_MORE, especially since the patch is already
> using it to store the type.

Just pondering whether it should be formalized, but probably no point as
each opcode should be free to use the space as it wants.

>> The above makes sense, but then what is IORING_TIMESTAMP_TSTYPE_SHIFT?
> 
> It's a shift for where the timestamp type is stored, HW vs SW is
> not a timestamp type. I don't get the question.

Please add a spec like comment on top of it explaining the usage of the
upper bits in the flags field, then. I try to keep the io_uring.h uapi
header pretty well commented and documented.

-- 
Jens Axboe