tty: n_gsm line discipline

Add an implementation of GSM 0710 MUX. The implementation currently supports

- Basic and advanced framing (as either end of the link)
- UI or UIH data frames
- Adaption layer 1-4 (1 and 2 via tty, 3 and 4 as skbuff lists)
- Modem and control messages including the correct retry process
- Flow control

and exposes the MUX channels as a set of virtual tty devices including modem
signals. This is an experimental driver.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 8 insertions, 1 deletions

diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig
index 3141dd3b6e53..51a57009aec8 100644
--- a/drivers/char/Kconfig
+++ b/drivers/char/Kconfig
@@ -276,11 +276,18 @@ config N_HDLC
           Allows synchronous HDLC communications with tty device drivers that
           support synchronous HDLC such as the Microgate SyncLink adapter.
 
-          This driver can only be built as a module ( = code which can be
+          This driver can be built as a module ( = code which can be
           inserted in and removed from the running kernel whenever you want).
           The module will be called n_hdlc. If you want to do that, say M
           here.
 
+config N_GSM
+        tristate "GSM MUX line discipline support (EXPERIMENTAL)"
+        depends on EXPERIMENTAL
+        help
+          This line discipline provides support for the GSM MUX protocol and
+          presents the mux as a set of 61 individual tty devices.
+
 config RISCOM8
         tristate "SDL RISCom/8 card support"
         depends on SERIAL_NONSTANDARD