[PATCH 00/11] (v6) virtio: console: Fixes, new way of discovering ports

[Amit Shah <amit.shah@redhat.com>]

Hello,

This series reworks the ABI to allow port discovery (only) via the
control queue and enable multiport again.

In addition, it adds support for non-blocking write() support, which
means no spinning. This works fine with the recent patches that are on
qemu-devel.

Also included is removal of hvc_remove() as removing one such console
port causes other console ports (registered with hvc) to stall. This
has to be debugged in the hvc_console.c file, I'll do that later, but
we have a nice workaround for this: returning -EPIPE on any hvc
operations will make the hvc console core perform any cleanups for the
removed ports. Looks like we don't lose much by removing hvc_remove().

New in this version:
- Locking for the out_vq. Slightly changed version compared to the
  diff I sent earlier in that I don't lock inside
  reclaim_used_buffers() now, letting us use spin_lock_irq() instead
  of spin_lock_irqsave() from non-irq contexts.
- Remove extra line spotted by Rusty

Rusty, please apply for -next if all is well.

Amit Shah (11):
  Revert "virtio: disable multiport console support."
  virtio: console: Add a __send_control_msg() that can send messages
    without a valid port
  virtio: console: Let host know of port or device add failures
  virtio: console: Return -EPIPE to hvc_console if we lost the
    connection
  virtio: console: Don't call hvc_remove() on unplugging console ports
  virtio: console: Remove config work handler
  virtio: console: Move code around for future patches
  virtio: console: Use a control message to add ports
  virtio: console: Don't always create a port 0 if using multiport
  virtio: console: Rename wait_is_over() to will_read_block()
  virtio: console: Add support for nonblocking write()s

 drivers/char/virtio_console.c  |  605 ++++++++++++++++++++--------------------
 include/linux/virtio_console.h |   25 ++
 2 files changed, 334 insertions(+), 296 deletions(-)