Historically the N_TTY driver could never fail but this has become broken over
time. Rather than trying to rewrite half the ldisc layer to fix the breakage
introduce a second level of fallback with an N_NULL ldisc which cannot fail,
and thus restore the guarantees required by the ldisc layer.
We still try and fail to N_TTY first. It's much more useful to find yourself
back in your old ldisc (first attempt) or in N_TTY (second attempt), and while
I'm not aware of any code out there that makes those assumptions it's good to
drive(r) defensively.
Signed-off-by: Alan Cox <alan@linux.intel.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Tested-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Over in the staging tree, N_SPEAKUP is added, so to make life easier for
merging and other development, also reserve it in the tty tree.
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Some NFC controller supports UART as host interface.
As with SPI, a lot of code can be shared between vendor
drivers. This patch add the generic support of UART and
provides some extension API for vendor specific needs.
This code is strongly inspired by the Bluetooth HCI ldisc
implementation. NCI UART vendor drivers will have to register
themselves to this layer via nci_uart_register.
Underlying tty will have to be configured from user land
thanks to an ioctl.
Signed-off-by: Vincent Cuissard <cuissard@marvell.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Michael Kerrisk <mtk.manpages@gmail.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Dave Jones <davej@redhat.com>
