[PATCH 0/6] USB: serial: mxuport: improve tty operation support

[Crescent Hsieh]

This series improves the mxuport driver's handling of several tty
operations.

The first patch converts the driver's control reads to
usb_control_msg_recv(), which handles DMA-safe temporary buffers and
validates the returned transfer length.

The second patch initializes the cached modem status when opening a
port, preventing TIOCMGET from temporarily reporting stale input-line
state.

Patches three and four add optional stop and start callbacks to the USB
serial core and implement them in mxuport. This prevents the driver from
submitting new write data while tty output is stopped.

Patch five adds device-specific TCFLSH handling so that flush requests
also purge the corresponding device buffers and USB serial write FIFO.

The final patch adds a wait_until_sent callback. It retains the generic
USB-serial queue polling and adds a baud-dependent delay before
reporting transmit completion.

Crescent Hsieh (6):
  USB: serial: mxuport: use usb_control_msg_recv()
  USB: serial: mxuport: initialize modem status on open
  USB: serial: add stop and start callbacks
  USB: serial: mxuport: handle output flow control
  USB: serial: mxuport: handle TCFLSH buffer purge
  USB: serial: mxuport: wait for UART transmit completion

 drivers/usb/serial/mxuport.c    | 287 +++++++++++++++++++++++---------
 drivers/usb/serial/usb-serial.c |  18 ++
 include/linux/usb/serial.h      |   2 +
 3 files changed, 231 insertions(+), 76 deletions(-)

-- 
2.53.0