net-caif-driver: add CAIF serial driver (ldisc)

Add CAIF Serial driver. This driver is implemented as a line discipline.

caif_serial uses the following module parameters:
ser_use_stx - specifies if STart of frame eXtension is in use.
ser_loop    - sets the interface in loopback mode.
Signed-off-by: Sjur Braendeland <sjur.brandeland@stericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/Kconfig

@@ -2837,6 +2837,8 @@ source "drivers/ieee802154/Kconfig"
 
 source "drivers/s390/net/Kconfig"
 
+source "drivers/net/caif/Kconfig"
+
 config XEN_NETDEV_FRONTEND
 	tristate "Xen network device frontend driver"
 	depends on XEN

drivers/net/Makefile

@@ -290,5 +290,6 @@ obj-$(CONFIG_VIRTIO_NET) += virtio_net.o
 obj-$(CONFIG_SFC) += sfc/
 
 obj-$(CONFIG_WIMAX) += wimax/
+obj-$(CONFIG_CAIF) += caif/
 
 obj-$(CONFIG_OCTEON_MGMT_ETHERNET) += octeon/

drivers/net/caif/Kconfig

+#
+# CAIF physical drivers
+#
+
+if CAIF
+
+comment "CAIF transport drivers"
+
+config CAIF_TTY
+	tristate "CAIF TTY transport driver"
+	default n
+	---help---
+	The CAIF TTY transport driver is a Line Discipline (ldisc)
+	identified as N_CAIF. When this ldisc is opened from user space
+	it will redirect the TTY's traffic into the CAIF stack.
+
+endif # CAIF

drivers/net/caif/Makefile

+ifeq ($(CONFIG_CAIF_DEBUG),1)
+CAIF_DBG_FLAGS := -DDEBUG
+endif
+
+KBUILD_EXTRA_SYMBOLS=net/caif/Module.symvers
+
+ccflags-y := $(CAIF_FLAGS) $(CAIF_DBG_FLAGS)
+clean-dirs:= .tmp_versions
+clean-files:= Module.symvers modules.order *.cmd *~ \
+
+# Serial interface
+obj-$(CONFIG_CAIF_TTY) += caif_serial.o

include/linux/tty.h

@@ -23,7 +23,7 @@
  */
 #define NR_UNIX98_PTY_DEFAULT	4096      /* Default maximum for Unix98 ptys */
 #define NR_UNIX98_PTY_MAX	(1 << MINORBITS) /* Absolute limit */
-#define NR_LDISCS		20
+#define NR_LDISCS		21
 
 /* line disciplines */
 #define N_TTY		0
@@ -46,8 +46,8 @@
 #define N_GIGASET_M101	16	/* Siemens Gigaset M101 serial DECT adapter */
 #define N_SLCAN		17	/* Serial / USB serial CAN Adaptors */
 #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 */
 
 /*
  * This character is the same as _POSIX_VDISABLE: it cannot be used as