RFC Bluetooth: ISO: support setting send Time_Stamp and LE Read ISO TX Sync

Add support for userspace setting BT_SCM_PKT_SEQNUM and BT_SCM_PKT_ISO_TS as CMSG to provide timestamps and sequence numbers to controller.

Also support obtaining sent packet timestamps via HCI LE Read ISO TX Sync and transmitting those to user as HW timestamps.

User-provided BT_SCM_PKT_SEQNUM may make sense if userspace is not sending SDUs every interval, and it is in the best position to determine when it wanted things to be sent. Behavior of course varies per controller, so not sure how useful this is in practice, and if it's premature to expose this in case there will be future clarifications in the Core Specification (no idea about whether that's likely).

RFC since this is not satisfactorily tested on real hardware, and there may be some design questions and ugly bits here. Sending anyway since there seems to be interest in this.

I also send the series adding iso-tester + emulator tests.

Pauli Virtanen (2):
Bluetooth: ISO: allow userspace to set seqnum and timestamp for
sending
Bluetooth: produce HW TX timestamps for ISO from LE Read ISO TX Sync

 include/net/bluetooth/bluetooth.h |  2 +
 include/net/bluetooth/hci.h       |  2 +-
 include/net/bluetooth/hci_core.h  |  5 +-
 net/bluetooth/hci_conn.c          | 53 +++++++++++++++++++--
 net/bluetooth/hci_core.c          |  8 ++--
 net/bluetooth/hci_event.c         | 79 ++++++++++++++++++++++++++++++-
 net/bluetooth/iso.c               | 70 +++++++++++++++++++++++----
 7 files changed, 199 insertions(+), 20 deletions(-)

2.53.0