Johan writes:

USB-serial updates for 5.11-rc1

Here are the USB-serial updates for 5.11-rc1, including:

 - keyspan_pda write-implementation fixes
 - digi_acceleport write-wakeup fix
 - mos7720 parport-restore fix
 - mos7720 parport-tasklet removal
 - cp210x termios-handling cleanups
 - option device-flag fix
 - ftdi_sio GPIO CBUS-configuration improvements
 - removal of in_interrupt() uses

Included are also various clean ups.

All have been in linux-next with no reported issues.

* tag 'usb-serial-5.11-rc1' of https://git.kernel.org/pub/scm/linux/kernel/git/johan/usb-serial: (30 commits)
  USB: serial: ftdi_sio: log the CBUS GPIO validity
  USB: serial: ftdi_sio: drop GPIO line checking dead code
  USB: serial: ftdi_sio: report the valid GPIO lines to gpiolib
  USB: serial: option: add interface-number sanity check to flag handling
  USB: serial: cp210x: clean up dtr_rts()
  USB: serial: cp210x: refactor flow-control handling
  USB: serial: cp210x: drop flow-control debugging
  USB: serial: cp210x: set terminal settings on open
  USB: serial: cp210x: clean up line-control handling
  USB: serial: cp210x: return early on unchanged termios
  USB: serial: mos7720: defer state restore to a workqueue
  USB: serial: mos7720: fix parallel-port state restore
  USB: serial: remove write wait queue
  USB: serial: digi_acceleport: fix write-wakeup deadlocks
  USB: serial: keyspan_pda: drop redundant usb-serial pointer
  USB: serial: keyspan_pda: use BIT() macro
  USB: serial: keyspan_pda: clean up comments and whitespace
  USB: serial: keyspan_pda: clean up xircom/entrega support
  USB: serial: keyspan_pda: add write-fifo support
  USB: serial: keyspan_pda: increase transmitter threshold
  ...

The validity of the ftdi CBUS GPIO is pretty hidden so far,
and finding out *why* some GPIOs don't work is sometimes
hard to identify. So let's help the user by displaying the
map of the CBUS pins that are valid for a GPIO.

Suggested-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20201204164739.781812-4-maz@kernel.org
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
[johan: demote to KERN_DEBUG, rephrase messages, drop ftx-prog warning]
Signed-off-by: Johan Hovold <johan@kernel.org>

Now that gpiolib can track the validity of GPIO pins, there is no need
to check whether the line is valid in request().

Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20201204164739.781812-5-maz@kernel.org
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
[johan: amend commit message]
Signed-off-by: Johan Hovold <johan@kernel.org>

Since it is pretty common for only some of the CBUS lines to be
valid as GPIO lines, let's report such validity to the rest of
the kernel.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20201204164739.781812-3-maz@kernel.org
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Johan Hovold <johan@kernel.org>

Add an interface-number sanity check before testing the device flags to
avoid relying on undefined behaviour when left shifting in case a device
uses an interface number greater than or equal to BITS_PER_LONG (i.e. 64
or 32).

Reported-by: syzbot+8881b478dad0a7971f79@syzkaller.appspotmail.com
Fixes: c3a65808f04a ("USB: serial: option: reimplement interface masking")
Cc: stable@vger.kernel.org
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>

Clean up dtr_rts() by renaming the port parameter and adding missing
whitespace.

Signed-off-by: Johan Hovold <johan@kernel.org>

Add a helper function to be used to configure flow control.

The flow-control code was the last caller that relied on the
memset-on-failure behaviour of cp210x_read_reg_block(), which we can now
drop in favour of bailing out on errors when retrieving the flow-control
settings.

This should also simplify adding support for software flow control.

Signed-off-by: Johan Hovold <johan@kernel.org>

Drop some unnecessary flow-control debugging.

Signed-off-by: Johan Hovold <johan@kernel.org>

Unlike other drivers cp210x have been retrieving the current terminal
settings from the device on open and reflecting those in termios.

Due to how set_termios() used to be implemented, this saved a few
control requests on open but has instead caused problems like broken
flow control and has required adding workarounds for swapped
line-control in cp2108 and line-speed initialisation on cp2104.

This unusual implementation also complicates adding new features for no
good reason.

Rip out the corresponding code and the above mentioned workarounds and
instead initialise the terminal settings unconditionally on open.

Signed-off-by: Johan Hovold <johan@kernel.org>

Update the line-control settings in one request unconditionally instead
of setting the word-length, parity and stop-bit settings separately.

This avoids multiple requests when several settings are changed even if
this scheme could potentially also be used to detect unsupported device
settings. Since all device types but CP2101 appears to support all
settings, let's handle that one specifically and also report back the
unsupported settings properly through termios by clearing the
corresponding bits.

Also drop the related unnecessary debug printks.

Signed-off-by: Johan Hovold <johan@kernel.org>