[PATCH 0/9] thunderbolt: Introduce USB4STREAM

Mika Westerberg
2026-04-28T07:22:16Z

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/20260427081109.2337731-1-mika.westerberg@linux.intel.com/

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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