Add ISO/L2CAP socket ioctl() BTGETTXINFO which informs the user how long it took the kernel and controller to complete their sendmsg(), and how many sendmsg() are in socket and controller queues. This currently provides information of the latest packet only, in principle there could be a ringbuffer containing few latest packets, not clear if that would be useful. These patches allow fixing / working around controller(?) issue where two ISO streams in same group get desynchronized. Having accurate knowledge of the packet queue lengths, user application can drop packets if it detects the ISO streams are not in sync. Pipewire side: https://gitlab.freedesktop.org/pvir/pipewire/-/commits/iso-ts-test With this change, https://github.com/bluez/bluez/issues/515 is more or less fixed, and the sound server can figure out the total latency to audio rendering (tx latency + transport latency + presentation delay). For ISO, this can be changed to use LE Read ISO TX Sync, when the clock and sequence number synchronization issues there are figured out, and a quirk is added for controllers with nonfunctional implementation. For the L2CAP latency, I'll need to think a bit more what is the audio use case. Motivation was that AVDTP delay report values appear to be off by ~0..40 ms compared to observed audio latency and this amount can vary per connection and time, so not explained by unaccounted code algorithmic delays etc. Currently it's not clear if there is relation to TX side latency, so it may be down to receiver side implementation. This needs a bit more work to figure out, but the L2CAP patch is anyway here. Due to the possible fragmentation in ISO sendmsg(), it seems we anyway need the tx_info_queue thing and can't easily do it by counting packets, and L2CAP required part is small addition on top of that. TBD: iso-tester / l2cap-tester tests Pauli Virtanen (3): Bluetooth: add transmission latency tracking for ISO and ACL Bluetooth: ISO: add new ioctl() for reading tx latency Bluetooth: L2CAP: add new ioctl() for reading tx latency include/net/bluetooth/bluetooth.h | 39 +++++++++++ include/net/bluetooth/hci_core.h | 30 ++++++++ net/bluetooth/hci_conn.c | 110 +++++++++++++++++++++++++++++- net/bluetooth/hci_core.c | 14 ++++ net/bluetooth/hci_event.c | 66 ++++++++++++++++++ net/bluetooth/iso.c | 58 ++++++++++++++-- net/bluetooth/l2cap_core.c | 12 ++++ net/bluetooth/l2cap_sock.c | 50 +++++++++++++- 8 files changed, 372 insertions(+), 7 deletions(-) -- 2.44.0
