Pauli Virtanen wrote: > Add SOF_TIMESTAMPING_TX_COMPLETION, for requesting a software timestamp > when hardware reports a packet completed. > > Completion tstamp is useful for Bluetooth, as hardware timestamps do not > exist in the HCI specification except for ISO packets, and the hardware > has a queue where packets may wait. In this case the software SND > timestamp only reflects the kernel-side part of the total latency > (usually small) and queue length (usually 0 unless HW buffers > congested), whereas the completion report time is more informative of > the true latency. > > It may also be useful in other cases where HW TX timestamps cannot be > obtained and user wants to estimate an upper bound to when the TX > probably happened. > > Signed-off-by: Pauli Virtanen <pav@xxxxxx> > --- > > Notes: > v5: > - back to decoupled COMPLETION & SND, like in v3 > - BPF reporting not implemented here > > Documentation/networking/timestamping.rst | 8 ++++++++ > include/linux/skbuff.h | 7 ++++--- > include/uapi/linux/errqueue.h | 1 + > include/uapi/linux/net_tstamp.h | 6 ++++-- > net/core/skbuff.c | 2 ++ > net/ethtool/common.c | 1 + > net/socket.c | 3 +++ > 7 files changed, 23 insertions(+), 5 deletions(-) > > diff --git a/Documentation/networking/timestamping.rst b/Documentation/networking/timestamping.rst > index 61ef9da10e28..b8fef8101176 100644 > --- a/Documentation/networking/timestamping.rst > +++ b/Documentation/networking/timestamping.rst > @@ -140,6 +140,14 @@ SOF_TIMESTAMPING_TX_ACK: > cumulative acknowledgment. The mechanism ignores SACK and FACK. > This flag can be enabled via both socket options and control messages. > > +SOF_TIMESTAMPING_TX_COMPLETION: > + Request tx timestamps on packet tx completion. The completion Minor: double space above, grammar issue below "receives [packet] a". > + timestamp is generated by the kernel when it receives packet a > + completion report from the hardware. Hardware may report multiple > + packets at once, and completion timestamps reflect the timing of the > + report and not actual tx time. This flag can be enabled via both > + socket options and control messages. > + Otherwise the patch LGTM.
