On Tue, Mar 14, 2023 at 12:38:06PM +0200, Kamil Zaripov wrote: > > On 13 Mar 2023, at 20:35, Richard Cochran <richardcoch...@gmail.com> wrote: > > > > "It works for me" is not a strong argument. This software stack must > > work for everyone. > > I agree that “It works for me” is not enough to merge this patch. > > > Time stamping on top of a bridge interface won't > > fly in general, if I'm not mistaken. > > Can you explain the problems you see with timestamping in the interface on > top of a bridge? > > From my point of view when you call setsockopt(.., SO_TIMESTAMP**, > SOF_TIMESTAMPING_**_HARDWARE) > it does not matter if any network card on your system support hw timestamping > capabilities. > At this point network card only record all socket option values to the socket > structure: > https://elixir.bootlin.com/linux/latest/source/net/core/sock.c#L895. > Next during package send we check if socket have appropriate timestamping > flags, and if so > we copy this info to the sk_buff structure: > https://elixir.bootlin.com/linux/latest/source/include/net/sock.h#L2768. > At the end after package finally ready to be send in ndo_start_xmit > https://elixir.bootlin.com/linux/latest/source/include/linux/netdevice.h#L1401 > we either implement required times taping features or not. For example > igb driver checks if tx_flags in skb_buf have timestamping request > https://elixir.bootlin.com/linux/latest/source/drivers/net/ethernet/intel/igb/igb_main.c#L6432 > and ask hardware to timestamp frame. > > So I think that it doesn’t matter how complex your network configuration, > only think that matters is which network card will actually handle frames. > > But I’m neither linux kernel networking expert nor PTP expert. If I’m wrong > please correct me.
What will happen if the bridge floods the frame to 2 bridge ports, and both supports hardware TX timestamping? How many TX timestamps will be collected by the kernel, and more importantly, which ones? How many of those will be delivered to user space? Is ptp4l prepared to process more than one hardware TX timestamp per sent packet? _______________________________________________ Linuxptp-devel mailing list Linuxptp-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linuxptp-devel
