Lines Matching +full:software +full:- +full:generated
1 .. SPDX-License-Identifier: GPL-2.0
43 -------------------------------------------------------------
59 -------------------------------------------------------------------
72 ----------------------------------------------------------------------
97 Timestamps may also be generated for reasons other than being
102 Request rx timestamps generated by the network adapter.
106 are generated just after a device driver hands a packet to the
110 Request tx timestamps generated by the network adapter. This flag
115 are generated in the device driver as close as possible, but always
130 a timestamp is generated at each layer. This allows for fine
138 over-report measurement, because the timestamp is generated when all
148 generated control message. Changes to the bits take immediate
154 Report any software timestamps when available.
160 Report hardware timestamps as generated by
180 is derived from a per-socket u32 counter (that wraps). For datagram
227 received the packet and its length at layer 2. A valid (non-zero)
233 Request both hardware and software timestamps for outgoing packets
235 are enabled at the same time. If both timestamps are generated,
262 cmsg->cmsg_level = SOL_SOCKET;
263 cmsg->cmsg_type = SO_TIMESTAMPING;
264 cmsg->cmsg_len = CMSG_LEN(sizeof(__u32));
282 -------------------------
292 correlating a timestamp with data is non-trivial. A range of bytes
310 bytestreams, we chose that a timestamp is generated only when all
321 relevant sequence number in skb_shinfo(skb)->tskey. Because an skbuff
322 has only one such field, only one timestamp can be generated.
332 These precautions ensure that the timestamp is generated only when all
346 page (`man 7 socket`) describes how timestamps generated with
351 ----------------------------
374 feature. At least one field is non-zero at any time. Most timestamps
381 as linuxptp. For the PTP clock API, see Documentation/driver-api/ptp.rst.
385 software timestamp will be generated in the recvmsg() call and passed
386 in ts[0] when a real software timestamp is missing. This happens also
418 is the first if ts[2] is non-zero, the second otherwise, in which
446 Reading from the error queue is always a non-blocking operation. To
461 implicitly defined. ts[0] holds a software timestamp if set, ts[1]
482 the requested fine-grained filtering for incoming packets is not
509 /* possible values for hwtstamp_config->tx_type */
527 /* possible values for hwtstamp_config->rx_filter */
547 --------------------------------------------------------
565 Time stamps for outgoing packets are to be generated as follows:
567 - In hard_start_xmit(), check if (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP)
568 is set no-zero. If yes, then the driver is expected to do hardware time
570 - If this is possible for the skb and requested, then declare
572 SKBTX_IN_PROGRESS in skb_shinfo(skb)->tx_flags , e.g. with::
574 skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS;
579 software generated time stamps by the network subsystem.
580 - Driver should call skb_tx_timestamp() as close to passing sk_buff to hardware
581 as possible. skb_tx_timestamp() provides a software time stamp if requested
583 - As soon as the driver has sent the packet and/or obtained a
589 should not fall back to software time stamping. The rationale is that
591 software time stamping and therefore could lead to unexpected deltas
595 ----------------------------------------------------------
636 - ``.port_txtstamp()``: a hook called prior to the transmission of
638 This is required for two-step timestamping, since the hardware
641 packet so that it can re-enqueue the packet back into the socket's
644 in skb->cb and enqueue a tx skb queue. Typically, a switch will have a
647 key-value pairs of PTP sequence ID/message type/domain number and the
655 One-step TX timestamping do not require packet cloning, since there is
656 no follow-up message required by the PTP protocol (because the
659 to be re-enqueued into its socket's error queue.
661 - ``.port_rxtstamp()``: On RX, the BPF classifier is run by DSA to
666 timestamps might either be available in-band (through metadata in the
667 DSA header, or attached in other ways to the packet), or out-of-band
683 mii_timestamper`` and add a pointer to it in ``phydev->mii_ts``. The presence
691 - Checking, in ``.ndo_eth_ioctl``, whether ``phy_has_hwtstamp(netdev->phydev)``
695 - On RX, special intervention may or may not be needed, depending on the
698 ``skb_defer_rx_timestamp(skb)`` is necessary or not - and if it is, don't
700 enabled, and ``skb->dev->phydev->mii_ts`` exists, its ``.rxtstamp()`` hook
711 - On TX, again, special intervention might or might not be needed. The
712 function that calls the ``mii_ts->txtstamp()`` hook is named
716 drivers already perform for software timestamping purposes. Therefore, if a
717 MAC supports software timestamping, it does not need to do anything further
733 Stacked PHCs, especially DSA (but not only) - since that doesn't require any
735 all possible code paths - is that they uncover bugs which were impossible to
739 skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS;
750 the ``.ndo_eth_ioctl`` ("``priv->hwtstamp_tx_enabled == true``") and the
751 current skb requires a TX timestamp ("``skb_shinfo(skb)->tx_flags &
753 "``skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS``" flag. Note: as
761 "``skb_shinfo(skb)->tx_flags & SKBTX_IN_PROGRESS``" was set. With a stacked
768 "``skb_shinfo(skb)->tx_flags & SKBTX_IN_PROGRESS``", but also for
769 "``priv->hwtstamp_tx_enabled == true``". Because the rest of the system ensures