[PATCH v2 0/2] TTY: add rpmsg tty driver

From: Arnaud Pouliquen
Date: Fri May 10 2019 - 11:05:05 EST

This patch set introduces a TTY console on top of the RPMsg framework which
enables the following use cases:
- Provide a console to communicate easily with the remote processor
- Provide an interface to get the remote processor log traces without
ring buffer limitation.
- Ease the migration from MPU + MCU processors to multi core processors
(MPU and MCU integrated in one processor)

An alternative of this proposed solution would consist in using the virtio
The drawback with that solution is that it requires a specific virtio buffer
(in addition to the one already used for RPMsg) which does not fit with remote
processors with little memory. The proposed solution allows to multiplex the
console with the other rpmsg services, optimizing the memory.

The first patch adds an API to the rpmsg framework ('get buffer size') and the
second one is the rpmsg tty driver itself.

-V1 to V2:
- modify message structure to allow to data transmission but also
flow control
- add documentation file to describe message structure for remote
- add dtr/rts management
- disable termios modes that generates non optimized behavior on RPMsg
- replace rpmsg_send by rpmsg_trysend to not block the write
- suppress useless spinlock on read.
- miscellaneous fixes to improve robustness

Arnaud Pouliquen (2):
rpmsg: core: add possibility to get message payload length
tty: add rpmsg driver

Documentation/serial/tty_rpmsg.txt | 38 +++
drivers/rpmsg/rpmsg_core.c | 20 ++
drivers/rpmsg/rpmsg_internal.h | 2 +
drivers/rpmsg/virtio_rpmsg_bus.c | 11 +
drivers/tty/Kconfig | 9 +
drivers/tty/Makefile | 1 +
drivers/tty/rpmsg_tty.c | 479 +++++++++++++++++++++++++++++++++++++
include/linux/rpmsg.h | 10 +
8 files changed, 570 insertions(+)
create mode 100644 Documentation/serial/tty_rpmsg.txt
create mode 100644 drivers/tty/rpmsg_tty.c