Lines Matching +full:clock +full:- +full:error +full:- +full:detect
1 .. SPDX-License-Identifier: GPL-2.0
43 -------------------------------------------------------------
59 -------------------------------------------------------------------
72 ----------------------------------------------------------------------
83 sk_buffs (1.3.1), timestamp reporting to the socket's error
138 over-report measurement, because the timestamp is generated when all
174 scheduler. In that case timestamps will be queued onto the error
181 is derived from a per-socket u32 counter (that wraps). For datagram
208 a timestamp with counter N-1. SOF_TIMESTAMPING_OPT_ID_TCP
258 received the packet and its length at layer 2. A valid (non-zero)
267 two separate messages will be looped to the socket's error queue,
283 ignore the unexpected non-zero value. But it makes behavior subtly
292 instance SOL_IP/IP_PKTINFO to detect the egress network interface.
310 cmsg->cmsg_level = SOL_SOCKET;
311 cmsg->cmsg_type = SO_TIMESTAMPING;
312 cmsg->cmsg_len = CMSG_LEN(sizeof(__u32));
330 -------------------------
340 correlating a timestamp with data is non-trivial. A range of bytes
369 relevant sequence number in skb_shinfo(skb)->tskey. Because an skbuff
373 collapsed onto the same skb. A process can detect this situation by
378 autocork. After linux-4.7, a better way to prevent coalescing is
400 ----------------------------
423 feature. At least one field is non-zero at any time. Most timestamps
427 Instead, expose the hardware clock device on the NIC directly as
428 a HW PTP clock source, to allow time conversion in userspace and
430 as linuxptp. For the PTP clock API, see Documentation/driver-api/ptp.rst.
442 socket's error queue with the send timestamp(s) attached. A process
449 embeds a struct sock_extended_err. This defines the error type. For
459 ee_info in the extended error structure. It contains a value of
467 is the first if ts[2] is non-zero, the second otherwise, in which
485 error queue mechanism is just a method to piggyback the timestamp on.
488 accordingly. Until the process calls recvmsg() on the error queue,
495 Reading from the error queue is always a non-blocking operation. To
497 POLLERR in pollfd.revents if any data is ready on the error queue.
505 On reception, there is no reason to read from the socket error queue.
507 on a normal recvmsg(). Since this is not a socket error, it is not
531 the requested fine-grained filtering for incoming packets is not
558 /* possible values for hwtstamp_config->tx_type */
576 /* possible values for hwtstamp_config->rx_filter */
596 --------------------------------------------------------
616 - In hard_start_xmit(), check if (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP)
617 is set no-zero. If yes, then the driver is expected to do hardware time
619 - If this is possible for the skb and requested, then declare
621 SKBTX_IN_PROGRESS in skb_shinfo(skb)->tx_flags , e.g. with::
623 skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS;
629 - Driver should call skb_tx_timestamp() as close to passing sk_buff to hardware
632 - As soon as the driver has sent the packet and/or obtained a
644 ----------------------------------------------------------
646 There are situations when there may be more than one PHC (PTP Hardware Clock)
666 switches include a timestamping clock of their own, and have the ability to
685 - ``.port_txtstamp()``: a hook called prior to the transmission of
687 This is required for two-step timestamping, since the hardware
690 packet so that it can re-enqueue the packet back into the socket's
691 error queue. To save the packet for when the timestamp becomes
693 in skb->cb and enqueue a tx skb queue. Typically, a switch will have a
696 key-value pairs of PTP sequence ID/message type/domain number and the
704 One-step TX timestamping do not require packet cloning, since there is
705 no follow-up message required by the PTP protocol (because the
708 to be re-enqueued into its socket's error queue.
710 - ``.port_rxtstamp()``: On RX, the BPF classifier is run by DSA to
715 timestamps might either be available in-band (through metadata in the
716 DSA header, or attached in other ways to the packet), or out-of-band
727 switches do. However, PHYs may be able to detect and timestamp PTP packets, for
732 mii_timestamper`` and add a pointer to it in ``phydev->mii_ts``. The presence
740 - Checking, in ``.ndo_eth_ioctl``, whether ``phy_has_hwtstamp(netdev->phydev)``
744 - On RX, special intervention may or may not be needed, depending on the
747 ``skb_defer_rx_timestamp(skb)`` is necessary or not - and if it is, don't
749 enabled, and ``skb->dev->phydev->mii_ts`` exists, its ``.rxtstamp()`` hook
760 - On TX, again, special intervention might or might not be needed. The
761 function that calls the ``mii_ts->txtstamp()`` hook is named
782 Stacked PHCs, especially DSA (but not only) - since that doesn't require any
784 all possible code paths - is that they uncover bugs which were impossible to
788 skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS;
799 the ``.ndo_eth_ioctl`` ("``priv->hwtstamp_tx_enabled == true``") and the
800 current skb requires a TX timestamp ("``skb_shinfo(skb)->tx_flags &
802 "``skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS``" flag. Note: as
810 "``skb_shinfo(skb)->tx_flags & SKBTX_IN_PROGRESS``" was set. With a stacked
817 "``skb_shinfo(skb)->tx_flags & SKBTX_IN_PROGRESS``", but also for
818 "``priv->hwtstamp_tx_enabled == true``". Because the rest of the system ensures