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

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

drivers/char/Makefile

@@ -40,6 +40,7 @@ obj-$(CONFIG_SYNCLINK)		+= synclink.o
 obj-$(CONFIG_SYNCLINKMP)	+= synclinkmp.o
 obj-$(CONFIG_SYNCLINK_GT)	+= synclink_gt.o
 obj-$(CONFIG_N_HDLC)		+= n_hdlc.o
+obj-$(CONFIG_N_GSM)		+= n_gsm.o
 obj-$(CONFIG_AMIGA_BUILTIN_SERIAL) += amiserial.o
 obj-$(CONFIG_SX)		+= sx.o generic_serial.o
 obj-$(CONFIG_RIO)		+= rio/ generic_serial.o

include/linux/gsmmux.h

+#ifndef _LINUX_GSMMUX_H
+#define _LINUX_GSMMUX_H
+
+struct gsm_config
+{
+	unsigned int adaption;
+	unsigned int encapsulation;
+	unsigned int initiator;
+	unsigned int t1;
+	unsigned int t2;
+	unsigned int t3;
+	unsigned int n2;
+	unsigned int mru;
+	unsigned int mtu;
+	unsigned int k;
+	unsigned int i;
+	unsigned int unused[8];		/* Padding for expansion without
+					   breaking stuff */
+};
+
+#define GSMIOC_GETCONF		_IOR('G', 0, struct gsm_config)
+#define GSMIOC_SETCONF		_IOW('G', 1, struct gsm_config)
+
+
+#endif

include/linux/tty.h

@@ -48,6 +48,7 @@
 #define N_PPS		18	/* Pulse per Second */
 #define N_V253		19	/* Codec control over voice modem */
 #define N_CAIF		20      /* CAIF protocol for talking to modems */
+#define N_GSM0710	21	/* GSM 0710 Mux */
 
 /*
  * This character is the same as _POSIX_VDISABLE: it cannot be used as