/* Copyright (c) 2004 Coraid, Inc.  See COPYING for GPL terms. */
/*
 * aoechr.c
 * AoE character device driver
 */

#include <linux/hdreg.h>
#include <linux/blkdev.h>
#include "aoe.h"

enum {
	//MINOR_STAT = 1, (moved to sysfs)
	MINOR_ERR = 2,
	MINOR_DISCOVER,
	MINOR_INTERFACES,
	MSGSZ = 2048,
	NARGS = 10,
	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 struct ErrMsg emsgs[NMSG];
static int emsgs_head_idx, emsgs_tail_idx;
static struct semaphore emsgs_sema;
static spinlock_t emsgs_lock;
static int nblocked_emsgs_readers;
static struct class_simple *aoe_class;
static struct aoe_chardev chardevs[] = {
	{ MINOR_ERR, "err" },
	{ MINOR_DISCOVER, "discover" },
	{ MINOR_INTERFACES, "interfaces" },
};

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_CRIT
		       "%s: could not set interface list: %s\n",
		       __FUNCTION__, "too many interfaces");
		return -EINVAL;
	}
	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 = kmalloc(n, GFP_ATOMIC);
	if (mp == NULL) {
		printk(KERN_CRIT "aoe: aoechr_error: allocation failure, len=%ld\n", n);
		goto bail;
	}

	memcpy(mp, msg, n);
	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)
		up(&emsgs_sema);
}

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: aoechr_write: can't write to that file.\n");
		break;
	case MINOR_DISCOVER:
		ret = discover();
		break;
	case MINOR_INTERFACES:
		ret = interfaces(buf, cnt);
		break;
	}
	if (ret == 0)
		ret = cnt;
	return ret;
}

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

	n = MINOR(inode->i_rdev);
	filp->private_data = (void *) (unsigned long) n;

	for (i = 0; i < ARRAY_SIZE(chardevs); ++i)
		if (chardevs[i].minor == n)
			return 0;
	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;
	switch (n) {
	case MINOR_ERR:
		spin_lock_irqsave(&emsgs_lock, flags);
loop:
		em = emsgs + emsgs_head_idx;
		if ((em->flags & EMFL_VALID) == 0) {
			if (filp->f_flags & O_NDELAY) {
				spin_unlock_irqrestore(&emsgs_lock, flags);
				return -EAGAIN;
			}
			nblocked_emsgs_readers++;

			spin_unlock_irqrestore(&emsgs_lock, flags);

			n = down_interruptible(&emsgs_sema);

			spin_lock_irqsave(&emsgs_lock, flags);

			nblocked_emsgs_readers--;

			if (n) {
				spin_unlock_irqrestore(&emsgs_lock, flags);
				return -ERESTARTSYS;
			}
			goto loop;
		}
		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;
	default:
		return -EFAULT;
	}
}

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

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

	n = register_chrdev(AOE_MAJOR, "aoechr", &aoe_fops);
	if (n < 0) { 
		printk(KERN_ERR "aoe: aoechr_init: can't register char device\n");
		return n;
	}
	sema_init(&emsgs_sema, 0);
	spin_lock_init(&emsgs_lock);
	aoe_class = class_simple_create(THIS_MODULE, "aoe");
	if (IS_ERR(aoe_class)) {
		unregister_chrdev(AOE_MAJOR, "aoechr");
		return PTR_ERR(aoe_class);
	}
	for (i = 0; i < ARRAY_SIZE(chardevs); ++i)
		class_simple_device_add(aoe_class,
					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)
		class_simple_device_remove(MKDEV(AOE_MAJOR, chardevs[i].minor));
	class_simple_destroy(aoe_class);
	unregister_chrdev(AOE_MAJOR, "aoechr");
}