tty: use u8 for flags

This makes all those 'char's an explicit 'u8'. This is part of the
continuing unification of chars and flags to be consistent u8.

This approaches tty_port_default_receive_buf().

Note that we do not change signedness as we compile with
-funsigned-char.

Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Cc: William Hubbs <w.d.hubbs@gmail.com>
Cc: Chris Brannon <chris@the-brannons.com>
Cc: Kirk Reiser <kirk@reisers.ca>
Cc: Samuel Thibault <samuel.thibault@ens-lyon.org>
Cc: Marcel Holtmann <marcel@holtmann.org>
Cc: Johan Hedberg <johan.hedberg@gmail.com>
Cc: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Max Staudt <max@enpas.org>
Cc: Wolfgang Grandegger <wg@grandegger.com>
Cc: Marc Kleine-Budde <mkl@pengutronix.de>
Cc: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Cc: Andreas Koensgen <ajk@comnets.uni-bremen.de>
Cc: Jeremy Kerr <jk@codeconstruct.com.au>
Cc: Matt Johnston <matt@codeconstruct.com.au>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Cc: Liam Girdwood <lgirdwood@gmail.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Jaroslav Kysela <perex@perex.cz>
Cc: Takashi Iwai <tiwai@suse.com>
Acked-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20230810091510.13006-18-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: use u8 for chars

This makes all those 'unsigned char's an explicit 'u8'. This is part of
the continuing unification of chars and flags to be consistent u8.

This approaches tty_port_default_receive_buf(). Flags to be next.

Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Cc: William Hubbs <w.d.hubbs@gmail.com>
Cc: Chris Brannon <chris@the-brannons.com>
Cc: Kirk Reiser <kirk@reisers.ca>
Cc: Samuel Thibault <samuel.thibault@ens-lyon.org>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Max Staudt <max@enpas.org>
Cc: Wolfgang Grandegger <wg@grandegger.com>
Cc: Marc Kleine-Budde <mkl@pengutronix.de>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Cc: Andreas Koensgen <ajk@comnets.uni-bremen.de>
Cc: Jeremy Kerr <jk@codeconstruct.com.au>
Cc: Matt Johnston <matt@codeconstruct.com.au>
Cc: Liam Girdwood <lgirdwood@gmail.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Jaroslav Kysela <perex@perex.cz>
Cc: Takashi Iwai <tiwai@suse.com>
Cc: Peter Ujfalusi <peter.ujfalusi@gmail.com>
Acked-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20230810091510.13006-17-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: make tty_ldisc_ops::*buf*() hooks operate on size_t

Count passed to tty_ldisc_ops::receive_buf*(), ::lookahead_buf(), and
returned from ::receive_buf2() is expected to be size_t. So set it to
size_t to unify with the rest of the code.

Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Cc: William Hubbs <w.d.hubbs@gmail.com>
Cc: Chris Brannon <chris@the-brannons.com>
Cc: Kirk Reiser <kirk@reisers.ca>
Cc: Samuel Thibault <samuel.thibault@ens-lyon.org>
Cc: Marcel Holtmann <marcel@holtmann.org>
Cc: Johan Hedberg <johan.hedberg@gmail.com>
Cc: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Max Staudt <max@enpas.org>
Cc: Wolfgang Grandegger <wg@grandegger.com>
Cc: Marc Kleine-Budde <mkl@pengutronix.de>
Cc: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Cc: Andreas Koensgen <ajk@comnets.uni-bremen.de>
Cc: Jeremy Kerr <jk@codeconstruct.com.au>
Cc: Matt Johnston <matt@codeconstruct.com.au>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Cc: Liam Girdwood <lgirdwood@gmail.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Jaroslav Kysela <perex@perex.cz>
Cc: Takashi Iwai <tiwai@suse.com>
Acked-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20230810091510.13006-16-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

mctp: serial: Fix starting value for frame check sequence

RFC1662 defines the start state for the crc16 FCS to be 0xffff, but
we're currently starting at zero.

This change uses the correct start state. We're only early in the
adoption for the serial binding, so there aren't yet any other users to
interface to.

Fixes: a0c2ccd9b5ad ("mctp: Add MCTP-over-serial transport binding")
Reported-by: Harsh Tyagi <harshtya@google.com>
Tested-by: Harsh Tyagi <harshtya@google.com>
Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

mctp: serial: Use netif_rx().

Since commit
baebdf48c3600 ("net: dev: Makes sure netif_rx() can be invoked in any context.")

the function netif_rx() can be used in preemptible/thread context as
well as in interrupt context.

Use netif_rx().

Cc: Jeremy Kerr <jk@codeconstruct.com.au>
Cc: Matt Johnston <matt@codeconstruct.com.au>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

mctp: serial: Cancel pending work from ndo_uninit handler

We cannot do the cancel_work_sync from after the unregister_netdev, as
the dev pointer is no longer valid, causing a uaf on ldisc unregister
(or device close).

Instead, do the cancel_work_sync from the ndo_uninit op, where the dev
still exists, but the queue has stopped.

Fixes: 7bd9890f3d74 ("mctp: serial: cancel tx work on ldisc close")
Reported-by: Luo Likang <luolikang@nsfocus.com>
Tested-by: Luo Likang <luolikang@nsfocus.com>
Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Link: https://lore.kernel.org/r/20220211011552.1861886-1-jk@codeconstruct.com.au
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

mctp: serial: remove unnecessary ldisc data check

Jiri assures me that a ldisc->open with tty->disc_data set should never
happen, so this check doesn't do anything.

Reported-by: Jiri Slaby <jirislaby@kernel.org>
Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

mctp: serial: enforce fixed MTU

The current serial driver requires a maximum MTU of 68, and it doesn't
make sense to set a MTU below the MCTP-required baseline (of 68) either.

This change sets the min_mtu & max_mtu of the mctp netdev, essentially
disallowing changes. By using these instead of a ndo_change_mtu op, we
get the netlink extacks reported too.

Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

mctp: serial: cancel tx work on ldisc close

We want to ensure that the tx work has finished before returning from
the ldisc close op, so do a synchronous cancel.

Reported-by: Jiri Slaby <jirislaby@kernel.org>
Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

mctp: Add MCTP-over-serial transport binding

This change adds a MCTP Serial transport binding, as defined by DMTF
specificiation DSP0253 - "MCTP Serial Transport Binding". This is
implemented as a new serial line discipline, and can be attached to
arbitrary tty devices.

From the Kconfig description:

This driver provides an MCTP-over-serial interface, through a
serial line-discipline, as defined by DMTF specification "DSP0253 -
MCTP Serial Transport Binding". By attaching the ldisc to a serial
device, we get a new net device to transport MCTP packets.

This allows communication with external MCTP endpoints which use
serial as their transport. It can also be used as an easy way to
provide MCTP connectivity between virtual machines, by forwarding
data between simple virtual serial devices.

Say y here if you need to connect to MCTP endpoints over serial. To
compile as a module, use m; the module will be called mctp-serial.

Once the N_MCTP line discipline is set [using ioctl(TCIOSETD)], we get a
new netdev suitable for MCTP communication.

The 'mctp' utility[1] provides a simple wrapper for this ioctl, using
'link serial <device>':

# mctp link serial /dev/ttyS0 &
# mctp link
dev lo index 1 address 0x00:00:00:00:00:00 net 1 mtu 65536 up
dev mctpserial0 index 5 address 0x(no-addr) net 1 mtu 68 down

[1]: https://github.com/CodeConstruct/mctp

Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>