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.
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| @@ -73,6 +73,7 @@ enum { · 72 unmodified lines | ||
| 73 | 73 | SCM_TSTAMP_SND, /* driver passed skb to NIC, or HW */ |
| 74 | 74 | SCM_TSTAMP_SCHED, /* data entered the packet scheduler */ |
| 75 | 75 | SCM_TSTAMP_ACK, /* data acknowledged by peer */ |
| 76 | + SCM_TSTAMP_COMPLETION, /* packet tx completion */ | |
| 76 | 77 | }; |
| 77 | 78 | |
| 78 | 79 | #endif /* _UAPI_LINUX_ERRQUEUE_H */ |