[PATCH v7 0/2] Add rpmsg tty driver

[Arnaud Pouliquen]

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 application.
- 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) by offering a virtual serial link.

An alternative of this proposed solution would consist in using the virtio
console:
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 max transmission unit')
and the second one is the rpmsg tty driver itself.

Previous revision:
- the patch 1/2 ("rpmsg: core: add API to get MTU) has been discussed in a
  separate thread on remoteproc mailing list:
    https://patchwork.kernel.org/patch/11333509/
- Previous version of the patch 2/2 (tty: add rpmsg driver) available here:
    https://patchwork.kernel.org/cover/11130213/

Main delta vs v6:
 - Pack the rpmsg_tty_ctrl struct.
 - MTU API acked by Suman Anna from Texas Intruments company. 

Arnaud Pouliquen (2):
  rpmsg: core: add API to get MTU
  tty: add rpmsg driver

 Documentation/serial/tty_rpmsg.rst |  45 ++++
 drivers/rpmsg/rpmsg_core.c         |  21 ++
 drivers/rpmsg/rpmsg_internal.h     |   2 +
 drivers/rpmsg/virtio_rpmsg_bus.c   |  10 +
 drivers/tty/Kconfig                |   9 +
 drivers/tty/Makefile               |   1 +
 drivers/tty/rpmsg_tty.c            | 417 +++++++++++++++++++++++++++++
 include/linux/rpmsg.h              |  10 +
 8 files changed, 515 insertions(+)
 create mode 100644 Documentation/serial/tty_rpmsg.rst
 create mode 100644 drivers/tty/rpmsg_tty.c

-- 
2.17.1