/* Copyright (c) 2012 Coraid, Inc.  See COPYING for GPL terms. */
/*
 * aoechr.c
 * AoE character device driver
 */

#include <linux/hdreg.h>
#include <linux/blkdev.h>
#include <linux/completion.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/mutex.h>
#include <linux/skbuff.h>
#include <linux/export.h>
#include "aoe.h"

enum {
        //MINOR_STAT = 1, (moved to sysfs)
        MINOR_ERR = 2,
        MINOR_DISCOVER,
        MINOR_INTERFACES,
        MINOR_REVALIDATE,
        MINOR_FLUSH,
        MSGSZ = 2048,
        NMSG = 100,             /* message backlog to retain */
};

struct aoe_chardev {
        ulong minor;
        char name[32];
};

enum { EMFL_VALID = 1 };

struct ErrMsg {
        short flags;
        short len;
        char *msg;
};

static DEFINE_MUTEX(aoechr_mutex);

/* A ring buffer of error messages, to be read through
 * "/dev/etherd/err".  When no messages are present,
 * readers will block waiting for messages to appear.
 */
static struct ErrMsg emsgs[NMSG];
static int emsgs_head_idx, emsgs_tail_idx;
static struct completion emsgs_comp;
static spinlock_t emsgs_lock;
static int nblocked_emsgs_readers;

static struct aoe_chardev chardevs[] = {
        { MINOR_ERR, "err" },
        { MINOR_DISCOVER, "discover" },
        { MINOR_INTERFACES, "interfaces" },
        { MINOR_REVALIDATE, "revalidate" },
        { MINOR_FLUSH, "flush" },
};

static char *aoe_devnode(const struct device *dev, umode_t *mode)
{
        return kasprintf(GFP_KERNEL, "etherd/%s", dev_name(dev));
}

static const struct class aoe_class = {
        .name = "aoe",
        .devnode = aoe_devnode,
};

static int
discover(void)
{
        aoecmd_cfg(0xffff, 0xff);
        return 0;
}

static int
interfaces(const char __user *str, size_t size)
{
        if (set_aoe_iflist(str, size)) {
                printk(KERN_ERR
                        "aoe: could not set interface list: too many interfaces\n");
                return -EINVAL;
        }
        return 0;
}

static int
revalidate(const char __user *str, size_t size)
{
        int major, minor, n;
        ulong flags;
        struct aoedev *d;
        struct sk_buff *skb;
        char buf[16];

        if (size >= sizeof buf)
                return -EINVAL;
        buf[sizeof buf - 1] = '\0';
        if (copy_from_user(buf, str, size))
                return -EFAULT;

        n = sscanf(buf, "e%d.%d", &major, &minor);
        if (n != 2) {
                pr_err("aoe: invalid device specification %s\n", buf);
                return -EINVAL;
        }
        d = aoedev_by_aoeaddr(major, minor, 0);
        if (!d)
                return -EINVAL;
        spin_lock_irqsave(&d->lock, flags);
        aoecmd_cleanslate(d);
        aoecmd_cfg(major, minor);
loop:
        skb = aoecmd_ata_id(d);
        spin_unlock_irqrestore(&d->lock, flags);
        /* try again if we are able to sleep a bit,
         * otherwise give up this revalidation
         */
        if (!skb && !msleep_interruptible(250)) {
                spin_lock_irqsave(&d->lock, flags);
                goto loop;
        }
        aoedev_put(d);
        if (skb) {
                struct sk_buff_head queue;
                __skb_queue_head_init(&queue);
                __skb_queue_tail(&queue, skb);
                aoenet_xmit(&queue);
        }
        return 0;
}

void
aoechr_error(char *msg)
{
        struct ErrMsg *em;
        char *mp;
        ulong flags, n;

        n = strlen(msg);

        spin_lock_irqsave(&emsgs_lock, flags);

        em = emsgs + emsgs_tail_idx;
        if ((em->flags & EMFL_VALID)) {
bail:           spin_unlock_irqrestore(&emsgs_lock, flags);
                return;
        }

        mp = kmemdup(msg, n, GFP_ATOMIC);
        if (!mp)
                goto bail;

        em->msg = mp;
        em->flags |= EMFL_VALID;
        em->len = n;

        emsgs_tail_idx++;
        emsgs_tail_idx %= ARRAY_SIZE(emsgs);

        spin_unlock_irqrestore(&emsgs_lock, flags);

        if (nblocked_emsgs_readers)
                complete(&emsgs_comp);
}

static ssize_t
aoechr_write(struct file *filp, const char __user *buf, size_t cnt, loff_t *offp)
{
        int ret = -EINVAL;

        switch ((unsigned long) filp->private_data) {
        default:
                printk(KERN_INFO "aoe: can't write to that file.\n");
                break;
        case MINOR_DISCOVER:
                ret = discover();
                break;
        case MINOR_INTERFACES:
                ret = interfaces(buf, cnt);
                break;
        case MINOR_REVALIDATE:
                ret = revalidate(buf, cnt);
                break;
        case MINOR_FLUSH:
                ret = aoedev_flush(buf, cnt);
                break;
        }
        if (ret == 0)
                ret = cnt;
        return ret;
}

static int
aoechr_open(struct inode *inode, struct file *filp)
{
        int n, i;

        mutex_lock(&aoechr_mutex);
        n = iminor(inode);
        filp->private_data = (void *) (unsigned long) n;

        for (i = 0; i < ARRAY_SIZE(chardevs); ++i)
                if (chardevs[i].minor == n) {
                        mutex_unlock(&aoechr_mutex);
                        return 0;
                }
        mutex_unlock(&aoechr_mutex);
        return -EINVAL;
}

static int
aoechr_rel(struct inode *inode, struct file *filp)
{
        return 0;
}

static ssize_t
aoechr_read(struct file *filp, char __user *buf, size_t cnt, loff_t *off)
{
        unsigned long n;
        char *mp;
        struct ErrMsg *em;
        ssize_t len;
        ulong flags;

        n = (unsigned long) filp->private_data;
        if (n != MINOR_ERR)
                return -EFAULT;

        spin_lock_irqsave(&emsgs_lock, flags);

        for (;;) {
                em = emsgs + emsgs_head_idx;
                if ((em->flags & EMFL_VALID) != 0)
                        break;
                if (filp->f_flags & O_NDELAY) {
                        spin_unlock_irqrestore(&emsgs_lock, flags);
                        return -EAGAIN;
                }
                nblocked_emsgs_readers++;

                spin_unlock_irqrestore(&emsgs_lock, flags);

                n = wait_for_completion_interruptible(&emsgs_comp);

                spin_lock_irqsave(&emsgs_lock, flags);

                nblocked_emsgs_readers--;

                if (n) {
                        spin_unlock_irqrestore(&emsgs_lock, flags);
                        return -ERESTARTSYS;
                }
        }
        if (em->len > cnt) {
                spin_unlock_irqrestore(&emsgs_lock, flags);
                return -EAGAIN;
        }
        mp = em->msg;
        len = em->len;
        em->msg = NULL;
        em->flags &= ~EMFL_VALID;

        emsgs_head_idx++;
        emsgs_head_idx %= ARRAY_SIZE(emsgs);

        spin_unlock_irqrestore(&emsgs_lock, flags);

        n = copy_to_user(buf, mp, len);
        kfree(mp);
        return n == 0 ? len : -EFAULT;
}

static const struct file_operations aoe_fops = {
        .write = aoechr_write,
        .read = aoechr_read,
        .open = aoechr_open,
        .release = aoechr_rel,
        .owner = THIS_MODULE,
        .llseek = noop_llseek,
};

int __init
aoechr_init(void)
{
        int n, i;

        n = register_chrdev(AOE_MAJOR, "aoechr", &aoe_fops);
        if (n < 0) {
                printk(KERN_ERR "aoe: can't register char device\n");
                return n;
        }
        init_completion(&emsgs_comp);
        spin_lock_init(&emsgs_lock);
        n = class_register(&aoe_class);
        if (n) {
                unregister_chrdev(AOE_MAJOR, "aoechr");
                return n;
        }

        for (i = 0; i < ARRAY_SIZE(chardevs); ++i)
                device_create(&aoe_class, NULL,
                              MKDEV(AOE_MAJOR, chardevs[i].minor), NULL,
                              chardevs[i].name);

        return 0;
}

void
aoechr_exit(void)
{
        int i;

        for (i = 0; i < ARRAY_SIZE(chardevs); ++i)
                device_destroy(&aoe_class, MKDEV(AOE_MAJOR, chardevs[i].minor));
        class_unregister(&aoe_class);
        unregister_chrdev(AOE_MAJOR, "aoechr");
}