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>

5 files changed, 473 insertions, 0 deletions

diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
index 4f1f9741c71d..da6657c11667 100644
--- a/drivers/net/Kconfig
+++ b/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
diff --git a/drivers/net/Makefile b/drivers/net/Makefile
index 478886234c28..ba06c1c0db8b 100644
--- a/drivers/net/Makefile
+++ b/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-$(CONFIG_OCTEON_MGMT_ETHERNET) += octeon/
diff --git a/drivers/net/caif/Kconfig b/drivers/net/caif/Kconfig
new file mode 100644
index 000000000000..0b28e0107697
--- /dev/null
+++ b/drivers/net/caif/Kconfig
@@ -0,0 +1,17 @@
+#
+# CAIF physical drivers
+#
+
+if CAIF
+
+comment "CAIF transport drivers"
+
+config CAIF_TTY
+        tristate "CAIF TTY transport driver"
+        default n
+        ---help---
+        The CAIF TTY transport driver is a Line Discipline (ldisc)
+        identified as N_CAIF. When this ldisc is opened from user space
+        it will redirect the TTY's traffic into the CAIF stack.
+
+endif # CAIF
diff --git a/drivers/net/caif/Makefile b/drivers/net/caif/Makefile
new file mode 100644
index 000000000000..52b6d1f826f8
--- /dev/null
+++ b/drivers/net/caif/Makefile
@@ -0,0 +1,12 @@
+ifeq ($(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
diff --git a/drivers/net/caif/caif_serial.c b/drivers/net/caif/caif_serial.c
new file mode 100644
index 000000000000..3502f607117f
--- /dev/null
+++ b/drivers/net/caif/caif_serial.c
@@ -0,0 +1,441 @@
+/*
+ * Copyright (C) ST-Ericsson AB 2010
+ * Author:      Sjur Brendeland / sjur.brandeland@stericsson.com
+ * License terms: GNU General Public License (GPL) version 2
+ */
+
+#include <linux/init.h>
+#include <linux/version.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/types.h>
+#include <linux/skbuff.h>
+#include <linux/netdevice.h>
+#include <linux/rtnetlink.h>
+#include <linux/tty.h>
+#include <linux/file.h>
+#include <linux/if_arp.h>
+#include <net/caif/caif_device.h>
+#include <net/caif/cfcnfg.h>
+#include <linux/err.h>
+#include <linux/debugfs.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Sjur Brendeland<sjur.brandeland@stericsson.com>");
+MODULE_DESCRIPTION("CAIF serial device TTY line discipline");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_LDISC(N_CAIF);
+
+#define SEND_QUEUE_LOW 10
+#define SEND_QUEUE_HIGH 100
+#define CAIF_SENDING            1 /* Bit 1 = 0x02*/
+#define CAIF_FLOW_OFF_SENT      4 /* Bit 4 = 0x10 */
+#define MAX_WRITE_CHUNK      4096
+#define ON 1
+#define OFF 0
+#define CAIF_MAX_MTU 4096
+
+/*This list is protected by the rtnl lock. */
+static LIST_HEAD(ser_list);
+
+static int ser_loop;
+module_param(ser_loop, bool, S_IRUGO);
+MODULE_PARM_DESC(ser_loop, "Run in simulated loopback mode.");
+
+static int ser_use_stx = 1;
+module_param(ser_use_stx, bool, S_IRUGO);
+MODULE_PARM_DESC(ser_use_stx, "STX enabled or not.");
+
+static int ser_use_fcs = 1;
+
+module_param(ser_use_fcs, bool, S_IRUGO);
+MODULE_PARM_DESC(ser_use_fcs, "FCS enabled or not.");
+
+static int ser_write_chunk = MAX_WRITE_CHUNK;
+module_param(ser_write_chunk, int, S_IRUGO);
+
+MODULE_PARM_DESC(ser_write_chunk, "Maximum size of data written to UART.");
+
+static struct dentry *debugfsdir;
+
+static int caif_net_open(struct net_device *dev);
+static int caif_net_close(struct net_device *dev);
+
+struct ser_device {
+        struct caif_dev_common common;
+        struct list_head node;
+        struct net_device *dev;
+        struct sk_buff_head head;
+        struct tty_struct *tty;
+        bool tx_started;
+        unsigned long state;
+        char *tty_name;
+#ifdef CONFIG_DEBUG_FS
+        struct dentry *debugfs_tty_dir;
+        struct debugfs_blob_wrapper tx_blob;
+        struct debugfs_blob_wrapper rx_blob;
+        u8 rx_data[128];
+        u8 tx_data[128];
+        u8 tty_status;
+
+#endif
+};
+
+static void caifdev_setup(struct net_device *dev);
+static void ldisc_tx_wakeup(struct tty_struct *tty);
+#ifdef CONFIG_DEBUG_FS
+static inline void update_tty_status(struct ser_device *ser)
+{
+        ser->tty_status =
+                ser->tty->stopped << 5 |
+                ser->tty->hw_stopped << 4 |
+                ser->tty->flow_stopped << 3 |
+                ser->tty->packet << 2 |
+                ser->tty->low_latency << 1 |
+                ser->tty->warned;
+}
+static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty)
+{
+        ser->debugfs_tty_dir =
+                        debugfs_create_dir(tty->name, debugfsdir);
+        if (!IS_ERR(ser->debugfs_tty_dir)) {
+                debugfs_create_blob("last_tx_msg", S_IRUSR,
+                                ser->debugfs_tty_dir,
+                                &ser->tx_blob);
+
+                debugfs_create_blob("last_rx_msg", S_IRUSR,
+                                ser->debugfs_tty_dir,
+                                &ser->rx_blob);
+
+                debugfs_create_x32("ser_state", S_IRUSR,
+                                ser->debugfs_tty_dir,
+                                (u32 *)&ser->state);
+
+                debugfs_create_x8("tty_status", S_IRUSR,
+                                ser->debugfs_tty_dir,
+                                &ser->tty_status);
+
+        }
+        ser->tx_blob.data = ser->tx_data;
+        ser->tx_blob.size = 0;
+        ser->rx_blob.data = ser->rx_data;
+        ser->rx_blob.size = 0;
+}
+
+static inline void debugfs_deinit(struct ser_device *ser)
+{
+        debugfs_remove_recursive(ser->debugfs_tty_dir);
+}
+
+static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size)
+{
+        if (size > sizeof(ser->rx_data))
+                size = sizeof(ser->rx_data);
+        memcpy(ser->rx_data, data, size);
+        ser->rx_blob.data = ser->rx_data;
+        ser->rx_blob.size = size;
+}
+
+static inline void debugfs_tx(struct ser_device *ser, const u8 *data, int size)
+{
+        if (size > sizeof(ser->tx_data))
+                size = sizeof(ser->tx_data);
+        memcpy(ser->tx_data, data, size);
+        ser->tx_blob.data = ser->tx_data;
+        ser->tx_blob.size = size;
+}
+#else
+static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty)
+{
+}
+
+static inline void debugfs_deinit(struct ser_device *ser)
+{
+}
+
+static inline void update_tty_status(struct ser_device *ser)
+{
+}
+
+static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size)
+{
+}
+
+static inline void debugfs_tx(struct ser_device *ser, const u8 *data, int size)
+{
+}
+
+#endif
+
+static void ldisc_receive(struct tty_struct *tty, const u8 *data,
+                        char *flags, int count)
+{
+        struct sk_buff *skb = NULL;
+        struct ser_device *ser;
+        int ret;
+        u8 *p;
+        ser = tty->disc_data;
+
+        /*
+         * NOTE: flags may contain information about break or overrun.
+         * This is not yet handled.
+         */
+
+
+        /*
+         * Workaround for garbage at start of transmission,
+         * only enable if STX handling is not enabled.
+         */
+        if (!ser->common.use_stx && !ser->tx_started) {
+                dev_info(&ser->dev->dev,
+                        "Bytes received before initial transmission -"
+                        "bytes discarded.\n");
+                return;
+        }
+
+        BUG_ON(ser->dev == NULL);
+
+        /* Get a suitable caif packet and copy in data. */
+        skb = netdev_alloc_skb(ser->dev, count+1);
+        BUG_ON(skb == NULL);
+        p = skb_put(skb, count);
+        memcpy(p, data, count);
+
+        skb->protocol = htons(ETH_P_CAIF);
+        skb_reset_mac_header(skb);
+        skb->dev = ser->dev;
+        debugfs_rx(ser, data, count);
+        /* Push received packet up the stack. */
+        ret = netif_rx_ni(skb);
+        if (!ret) {
+                ser->dev->stats.rx_packets++;
+                ser->dev->stats.rx_bytes += count;
+        } else
+                ++ser->dev->stats.rx_dropped;
+        update_tty_status(ser);
+}
+
+static int handle_tx(struct ser_device *ser)
+{
+        struct tty_struct *tty;
+        struct sk_buff *skb;
+        int tty_wr, len, room;
+        tty = ser->tty;
+        ser->tx_started = true;
+
+        /* Enter critical section */
+        if (test_and_set_bit(CAIF_SENDING, &ser->state))
+                return 0;
+
+        /* skb_peek is safe because handle_tx is called after skb_queue_tail */
+        while ((skb = skb_peek(&ser->head)) != NULL) {
+
+                /* Make sure you don't write too much */
+                len = skb->len;
+                room = tty_write_room(tty);
+                if (!room)
+                        break;
+                if (room > ser_write_chunk)
+                        room = ser_write_chunk;
+                if (len > room)
+                        len = room;
+
+                /* Write to tty or loopback */
+                if (!ser_loop) {
+                        tty_wr = tty->ops->write(tty, skb->data, len);
+                        update_tty_status(ser);
+                } else {
+                        tty_wr = len;
+                        ldisc_receive(tty, skb->data, NULL, len);
+                }
+                ser->dev->stats.tx_packets++;
+                ser->dev->stats.tx_bytes += tty_wr;
+
+                /* Error on TTY ?! */
+                if (tty_wr < 0)
+                        goto error;
+                /* Reduce buffer written, and discard if empty */
+                skb_pull(skb, tty_wr);
+                if (skb->len == 0) {
+                        struct sk_buff *tmp = skb_dequeue(&ser->head);
+                        BUG_ON(tmp != skb);
+                        if (in_interrupt())
+                                dev_kfree_skb_irq(skb);
+                        else
+                                kfree_skb(skb);
+                }
+        }
+        /* Send flow off if queue is empty */
+        if (ser->head.qlen <= SEND_QUEUE_LOW &&
+                test_and_clear_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
+                ser->common.flowctrl != NULL)
+                                ser->common.flowctrl(ser->dev, ON);
+        clear_bit(CAIF_SENDING, &ser->state);
+        return 0;
+error:
+        clear_bit(CAIF_SENDING, &ser->state);
+        return tty_wr;
+}
+
+static int caif_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+        struct ser_device *ser;
+        BUG_ON(dev == NULL);
+        ser = netdev_priv(dev);
+
+        /* Send flow off once, on high water mark */
+        if (ser->head.qlen > SEND_QUEUE_HIGH &&
+                !test_and_set_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
+                ser->common.flowctrl != NULL)
+
+                ser->common.flowctrl(ser->dev, OFF);
+
+        skb_queue_tail(&ser->head, skb);
+        return handle_tx(ser);
+}
+
+
+static void ldisc_tx_wakeup(struct tty_struct *tty)
+{
+        struct ser_device *ser;
+        ser = tty->disc_data;
+        BUG_ON(ser == NULL);
+        BUG_ON(ser->tty != tty);
+        handle_tx(ser);
+}
+
+
+static int ldisc_open(struct tty_struct *tty)
+{
+        struct ser_device *ser;
+        struct net_device *dev;
+        char name[64];
+        int result;
+
+        sprintf(name, "cf%s", tty->name);
+        dev = alloc_netdev(sizeof(*ser), name, caifdev_setup);
+        ser = netdev_priv(dev);
+        ser->tty = tty;
+        ser->dev = dev;
+        debugfs_init(ser, tty);
+        tty->receive_room = N_TTY_BUF_SIZE;
+        tty->disc_data = ser;
+        set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
+        rtnl_lock();
+        result = register_netdevice(dev);
+        if (result) {
+                rtnl_unlock();
+                free_netdev(dev);
+                return -ENODEV;
+        }
+
+        list_add(&ser->node, &ser_list);
+        rtnl_unlock();
+        netif_stop_queue(dev);
+        update_tty_status(ser);
+        return 0;
+}
+
+static void ldisc_close(struct tty_struct *tty)
+{
+        struct ser_device *ser = tty->disc_data;
+        /* Remove may be called inside or outside of rtnl_lock */
+        int islocked = rtnl_is_locked();
+        if (!islocked)
+                rtnl_lock();
+        /* device is freed automagically by net-sysfs */
+        dev_close(ser->dev);
+        unregister_netdevice(ser->dev);
+        list_del(&ser->node);
+        debugfs_deinit(ser);
+        if (!islocked)
+                rtnl_unlock();
+}
+
+/* The line discipline structure. */
+static struct tty_ldisc_ops caif_ldisc = {
+        .owner =        THIS_MODULE,
+        .magic =        TTY_LDISC_MAGIC,
+        .name =         "n_caif",
+        .open =         ldisc_open,
+        .close =        ldisc_close,
+        .receive_buf =  ldisc_receive,
+        .write_wakeup = ldisc_tx_wakeup
+};
+
+static int register_ldisc(void)
+{
+        int result;
+        result = tty_register_ldisc(N_CAIF, &caif_ldisc);
+        if (result < 0) {
+                pr_err("cannot register CAIF ldisc=%d err=%d\n", N_CAIF,
+                        result);
+                return result;
+        }
+        return result;
+}
+static const struct net_device_ops netdev_ops = {
+        .ndo_open = caif_net_open,
+        .ndo_stop = caif_net_close,
+        .ndo_start_xmit = caif_xmit
+};
+
+static void caifdev_setup(struct net_device *dev)
+{
+        struct ser_device *serdev = netdev_priv(dev);
+        dev->features = 0;
+        dev->netdev_ops = &netdev_ops;
+        dev->type = ARPHRD_CAIF;
+        dev->flags = IFF_POINTOPOINT | IFF_NOARP;
+        dev->mtu = CAIF_MAX_MTU;
+        dev->hard_header_len = CAIF_NEEDED_HEADROOM;
+        dev->tx_queue_len = 0;
+        dev->destructor = free_netdev;
+        skb_queue_head_init(&serdev->head);
+        serdev->common.link_select = CAIF_LINK_LOW_LATENCY;
+        serdev->common.use_frag = true;
+        serdev->common.use_stx = ser_use_stx;
+        serdev->common.use_fcs = ser_use_fcs;
+        serdev->dev = dev;
+}
+
+
+static int caif_net_open(struct net_device *dev)
+{
+        struct ser_device *ser;
+        ser = netdev_priv(dev);
+        netif_wake_queue(dev);
+        return 0;
+}
+
+static int caif_net_close(struct net_device *dev)
+{
+        netif_stop_queue(dev);
+        return 0;
+}
+
+static int __init caif_ser_init(void)
+{
+        int ret;
+        ret = register_ldisc();
+        debugfsdir = debugfs_create_dir("caif_serial", NULL);
+        return ret;
+}
+
+static void __exit caif_ser_exit(void)
+{
+        struct ser_device *ser = NULL;
+        struct list_head *node;
+        struct list_head *_tmp;
+        list_for_each_safe(node, _tmp, &ser_list) {
+                ser = list_entry(node, struct ser_device, node);
+                dev_close(ser->dev);
+                unregister_netdevice(ser->dev);
+                list_del(node);
+        }
+        tty_unregister_ldisc(N_CAIF);
+        debugfs_remove_recursive(debugfsdir);
+}
+
+module_init(caif_ser_init);
+module_exit(caif_ser_exit);