thunderbolt: Introduce USB4STREAM

Hi all,

This series adds support for a new protocol over USB4/Thunderbolt cable
called USB4STREAM. The protocol is super-simple and basically just
transfers raw packets from one host to another. It is documented as part of
the thunderbolt_stream driver.

The driver exposes /dev/tbstreamX devices on each side of the link that can
be used to transfer data using regular filesystem operations such as
read(2) and write(2):

  host1 # cat /dev/tbstream0
  host2 # echo hello > /dev/tbstream0

This can be useful in cases where network tooling is not available or just
for existing applications like 'dd' and 'cat' that do not support sockets.

thunderbolt_stream can be used at the same time with thunderbolt_net so
they don't rule each other our. 

thunderbolt_stream allows multiple streams to be created, for example one
stream for control traffic and another for data (there are some limitations
in the core USB4/Thunderbolt driver due to dedicated flow control scheme
but this is likely change in the future). Each stream is bi-directional
tunnel over the fabric.

There are a couple of additional usage examples in the last patch that adds
the driver itself.

This applies on top of my XDomain improvements series [1].

[1] https://lore.kernel.org/linux-usb/20260427081109.2337731-...

Mika Westerberg (9):
  thunderbolt: Add tb_property_merge_dir()
  thunderbolt: Add KUnit test for tb_property_merge_dir()
  thunderbolt: Allow service drivers to specify their own properties
  thunderbolt / net: Move ring_frame_size() to thunderbolt.h
  thunderbolt / net: Let the service drivers configure interrupt throttling
  thunderbolt: Add helper to figure size of the ring
  thunderbolt: Add tb_ring_flush()
  thunderbolt: Add support for ConfigFS
  thunderbolt: Add support for USB4STREAM

 .../ABI/testing/configfs-thunderbolt_stream   |   77 +
 drivers/net/thunderbolt/main.c                |   23 +-
 drivers/thunderbolt/Kconfig                   |   15 +
 drivers/thunderbolt/Makefile                  |    4 +
 drivers/thunderbolt/configfs.c                |   61 +
 drivers/thunderbolt/dma_test.c                |    5 +
 drivers/thunderbolt/domain.c                  |    2 +
 drivers/thunderbolt/nhi.c                     |   86 +-
 drivers/thunderbolt/nhi_regs.h                |    3 +-
 drivers/thunderbolt/property.c                |  154 +-
 drivers/thunderbolt/stream.c                  | 1693 +++++++++++++++++
 drivers/thunderbolt/tb.h                      |    8 +
 drivers/thunderbolt/test.c                    |   82 +
 drivers/thunderbolt/xdomain.c                 |   95 +-
 include/linux/thunderbolt.h                   |   44 +-
 15 files changed, 2257 insertions(+), 95 deletions(-)
 create mode 100644 Documentation/ABI/testing/configfs-thunderbolt_stream
 create mode 100644 drivers/thunderbolt/configfs.c
 create mode 100644 drivers/thunderbolt/stream.c

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2.50.1