caif_serial.c

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/*
 * Copyright (C) ST-Ericsson AB 2010
 * Author:  Sjur Brendeland / [email protected]
 * License terms: GNU General Public License (GPL) version 2
 */

#include <linux/hardirq.h>
#include <linux/init.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<[email protected]>");
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 bool ser_loop;
module_param(ser_loop, bool, S_IRUGO);
MODULE_PARM_DESC(ser_loop, "Run in simulated loopback mode.");

static bool ser_use_stx = true;
module_param(ser_use_stx, bool, S_IRUGO);
MODULE_PARM_DESC(ser_use_stx, "STX enabled or not.");

static bool ser_use_fcs = true;

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);
    if (skb == NULL)
        return;
    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);
            WARN_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);
    WARN_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;

    /* No write no play */
    if (tty->ops->write == NULL)
        return -EOPNOTSUPP;
    if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_TTY_CONFIG))
        return -EPERM;

    sprintf(name, "cf%s", tty->name);
    dev = alloc_netdev(sizeof(*ser), name, caifdev_setup);
    if (!dev)
        return -ENOMEM;

    ser = netdev_priv(dev);
    ser->tty = tty_kref_get(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);
    tty_kref_put(ser->tty);
    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->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)
{
    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);