On 1/10/21 1:49 PM, Vincent Mailhol wrote: > Call skb_tx_timestamp() within can_put_echo_skb() so that a software > tx timestamp gets attached on the skb. > > There two main reasons to include this call in can_put_echo_skb(): > > * It easily allow to enable the tx timestamp on all devices with > just one small change. > > * According to Documentation/networking/timestamping.rst, the tx > timestamps should be generated in the device driver as close as > possible, but always prior to passing the packet to the network > interface. During the call to can_put_echo_skb(), the skb gets > cloned meaning that the driver should not dereference the skb > variable anymore after can_put_echo_skb() returns. This makes > can_put_echo_skb() the very last place we can use the skb without > having to access the echo_skb[] array. > > Remarks: > > * By default, skb_tx_timestamp() does nothing. It needs to be > activated by passing the SOF_TIMESTAMPING_TX_SOFTWARE flag either > through socket options or control messages. > > * The hardware rx timestamp of a local loopback message is the > hardware tx timestamp. This means that there are no needs to > implement SOF_TIMESTAMPING_TX_HARDWARE for CAN sockets. > > References: > > Support for the error queue in CAN RAW sockets (which is needed for tx > timestamps) was introduced in: > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=eb88531bdbfaafb827192d1fc6c5a3fcc4fadd96 > > Put the call to skb_tx_timestamp() just before adding it to the array: > https://lkml.org/lkml/2021/1/10/54 > > Signed-off-by: Vincent Mailhol <mailhol.vincent@xxxxxxxxxx> Applied to linux-can-next/testing (ontop of my dev infrastructure cleanup). regards, Marc -- Pengutronix e.K. | Marc Kleine-Budde | Embedded Linux | https://www.pengutronix.de | Vertretung West/Dortmund | Phone: +49-231-2826-924 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
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