path: root/drivers/net/sdla_fr.c

/*****************************************************************************
* sdla_fr.c	WANPIPE(tm) Multiprotocol WAN Link Driver. Frame relay module.
*
* Author:	Gene Kozin	<genek@compuserve.com>
*
* Copyright:	(c) 1995-1997 Sangoma Technologies Inc.
*
*		This program is free software; you can redistribute it and/or
*		modify it under the terms of the GNU General Public License
*		as published by the Free Software Foundation; either version
*		2 of the License, or (at your option) any later version.
* ============================================================================
* Jan 02, 1997	Gene Kozin	Initial version.
*****************************************************************************/

#if	!defined(__KERNEL__) || !defined(MODULE)
#error	This code MUST be compiled as a kernel module!
#endif

#include <linux/kernel.h>	/* printk(), and other useful stuff */
#include <linux/stddef.h>	/* offsetof(), etc. */
#include <linux/errno.h>	/* return codes */
#include <linux/string.h>	/* inline memset(), etc. */
#include <linux/malloc.h>	/* kmalloc(), kfree() */
#include <linux/router.h>	/* WAN router definitions */
#include <linux/wanpipe.h>	/* WANPIPE common user API definitions */
#include <linux/if_arp.h>	/* ARPHRD_* defines */
#include <linux/init.h>		/* __initfunc et al. */
#include <asm/byteorder.h>	/* htons(), etc. */
#include <asm/io.h>		/* for inb(), outb(), etc. */

#define	_GNUC_
#include <linux/sdla_fr.h>	/* frame relay firmware API definitions */

/****** Defines & Macros ****************************************************/

#define	CMD_OK		0		/* normal firmware return code */
#define	CMD_TIMEOUT	0xFF		/* firmware command timed out */
#define	MAX_CMD_RETRY	10		/* max number of firmware retries */

#define	FR_HEADER_LEN	8		/* max encapsulation header size */
#define	FR_CHANNEL_MTU	1500		/* unfragmented logical channel MTU */

/* Q.922 frame types */
#define	Q922_UI		0x03		/* Unnumbered Info frame */
#define	Q922_XID	0xAF		/* ??? */

/****** Data Structures *****************************************************/

/* This is an extention of the 'struct device' we create for each network
 * interface to keep the rest of channel-specific data.
 */
typedef struct fr_channel
{
	char name[WAN_IFNAME_SZ+1];	/* interface name, ASCIIZ */
	unsigned dlci;			/* logical channel number */
	unsigned cir;			/* committed information rate */
	char state;			/* channel state */
	unsigned long state_tick;	/* time of the last state change */
	sdla_t* card;			/* -> owner */
	struct enet_statistics ifstats;	/* interface statistics */
} fr_channel_t;

typedef struct dlci_status
{
	unsigned short dlci	PACKED;
	unsigned char state	PACKED;
} dlci_status_t;

/****** Function Prototypes *************************************************/

/* WAN link driver entry points. These are called by the WAN router module. */
static int update (wan_device_t* wandev);
static int new_if (wan_device_t* wandev, struct device* dev,
	wanif_conf_t* conf);
static int del_if (wan_device_t* wandev, struct device* dev);

/* Network device interface */
static int if_init   (struct device* dev);
static int if_open   (struct device* dev);
static int if_close  (struct device* dev);
static int if_header (struct sk_buff* skb, struct device* dev,
	unsigned short type, void* daddr, void* saddr, unsigned len);
static int if_rebuild_hdr (void* hdr, struct device* dev, unsigned long raddr,
	struct sk_buff* skb);
static int if_send (struct sk_buff* skb, struct device* dev);
static struct enet_statistics* if_stats (struct device* dev);

/* Interrupt handlers */
static void fr502_isr (sdla_t* card);
static void fr508_isr (sdla_t* card);
static void fr502_rx_intr (sdla_t* card);
static void fr508_rx_intr (sdla_t* card);
static void tx_intr (sdla_t* card);
static void spur_intr (sdla_t* card);

/* Background polling routines */
static void wpf_poll (sdla_t* card);

/* Frame relay firmware interface functions */
static int fr_read_version (sdla_t* card, char* str);
static int fr_configure (sdla_t* card, fr_conf_t *conf);
static int fr_set_intr_mode (sdla_t* card, unsigned mode, unsigned mtu);
static int fr_comm_enable (sdla_t* card);
static int fr_comm_disable (sdla_t* card);
static int fr_add_dlci (sdla_t* card, int dlci, int num);
static int fr_activate_dlci (sdla_t* card, int dlci, int num);
static int fr_issue_isf (sdla_t* card, int isf);
static int fr502_send (sdla_t* card, int dlci, int attr, int len, void *buf);
static int fr508_send (sdla_t* card, int dlci, int attr, int len, void *buf);

/* Firmware asynchronous event handlers */
static int fr_event (sdla_t* card, int event, fr_mbox_t* mbox);
static int fr_modem_failure (sdla_t *card, fr_mbox_t* mbox);
static int fr_dlci_change (sdla_t *card, fr_mbox_t* mbox);

/* Miscellaneous functions */
static int update_chan_state (struct device* dev);
static void set_chan_state (struct device* dev, int state);
static struct device* find_channel (sdla_t* card, unsigned dlci);
static int is_tx_ready (sdla_t* card);
static unsigned int dec_to_uint (unsigned char* str, int len);
static unsigned int hex_to_uint (unsigned char* str, int len);

/****** Public Functions ****************************************************/

/*============================================================================
 * Frame relay protocol initialization routine.
 *
 * This routine is called by the main WANPIPE module during setup.  At this
 * point adapter is completely initialized and firmware is running.
 *  o read firmware version (to make sure it's alive)
 *  o configure adapter
 *  o initialize protocol-specific fields of the adapter data space.
 *
 * Return:	0	o.k.
 *		< 0	failure.
 */
__initfunc(int wpf_init (sdla_t* card, wandev_conf_t* conf))
{
	union
	{
		char str[80];
		fr_conf_t cfg;
	} u;

	/* Verify configuration ID */
	if (conf->config_id != WANCONFIG_FR)
	{
		printk(KERN_INFO "%s: invalid configuration ID %u!\n",
			card->devname, conf->config_id)
		;
		return -EINVAL;
	}

	/* Initialize protocol-specific fields of adapter data space */
	switch (card->hw.fwid)
	{
	case SFID_FR502:
		card->mbox  = (void*)(card->hw.dpmbase + FR502_MBOX_OFFS);
		card->rxmb  = (void*)(card->hw.dpmbase + FR502_RXMB_OFFS);
		card->flags = (void*)(card->hw.dpmbase + FR502_FLAG_OFFS);
		card->isr = &fr502_isr;
		break;

	case SFID_FR508:
		card->mbox  = (void*)(card->hw.dpmbase + FR508_MBOX_OFFS);
		card->flags = (void*)(card->hw.dpmbase + FR508_FLAG_OFFS);
		card->isr = &fr508_isr;
		break;

	default:
		return -EINVAL;
	}

	/* Read firmware version.  Note that when adapter initializes, it
	 * clears the mailbox, so it may appear that the first command was
	 * executed successfully when in fact it was merely erased. To work
	 * around this, we execute the first command twice.
	 */
	if (fr_read_version(card, NULL) || fr_read_version(card, u.str))
		return -EIO
	;
	printk(KERN_INFO "%s: running frame relay firmware v%s\n",
		card->devname, u.str)
	;

	/* Adjust configuration */
	conf->mtu = max(min(conf->mtu, 4080), FR_CHANNEL_MTU + FR_HEADER_LEN);
	conf->bps = min(conf->bps, 2048000);

	/* Configure adapter firmware */
	memset(&u.cfg, 0, sizeof(u.cfg));
	u.cfg.mtu	= conf->mtu;
	u.cfg.t391	= 10;
	u.cfg.t392	= 15;
	u.cfg.n391	= 6;
	u.cfg.n392	= 3;
	u.cfg.n393	= 4;
	u.cfg.kbps	= conf->bps / 1000;
	u.cfg.cir_fwd	= max(min(u.cfg.kbps, 512), 1);
	u.cfg.cir_bwd = u.cfg.bc_fwd = u.cfg.bc_bwd = u.cfg.cir_fwd;
	u.cfg.options	= 0x0081;	/* direct Rx, no CIR check */
	switch (conf->u.fr.signalling)
	{
	case WANOPT_FR_Q933:	u.cfg.options |= 0x0200; break;
	case WANOPT_FR_LMI:	u.cfg.options |= 0x0400; break;
	}
	if (conf->station == WANOPT_CPE)
	{
		u.cfg.options |= 0x8000;	/* auto config DLCI */
	}
	else
	{
		u.cfg.station = 1;	/* switch emulation mode */
		card->u.f.node_dlci = conf->u.fr.dlci ? conf->u.fr.dlci : 16;
		card->u.f.dlci_num  = max(min(conf->u.fr.dlci_num, 1), 100);
	}
	if (conf->clocking == WANOPT_INTERNAL)
		u.cfg.port |= 0x0001
	;
	if (conf->interface == WANOPT_RS232)
		u.cfg.port |= 0x0002
	;
	if (conf->u.fr.t391)
		u.cfg.t391 = min(conf->u.fr.t391, 30)
	;
	if (conf->u.fr.t392)
		u.cfg.t392 = min(conf->u.fr.t392, 30)
	;
	if (conf->u.fr.n391)
		u.cfg.n391 = min(conf->u.fr.n391, 255)
	;
	if (conf->u.fr.n392)
		u.cfg.n392 = min(conf->u.fr.n392, 10)
	;
	if (conf->u.fr.n393)
		u.cfg.n393 = min(conf->u.fr.n393, 10)
	;

	if (fr_configure(card, &u.cfg))
		return -EIO
	;

	if (card->hw.fwid == SFID_FR508)
	{
		fr_buf_info_t* buf_info =
			(void*)(card->hw.dpmbase + FR508_RXBC_OFFS)
		;

		card->rxmb =
			(void*)(buf_info->rse_next -
			FR_MB_VECTOR + card->hw.dpmbase)
		;
		card->u.f.rxmb_base =
			(void*)(buf_info->rse_base -
			FR_MB_VECTOR + card->hw.dpmbase)
		;
		card->u.f.rxmb_last =
			(void*)(buf_info->rse_base +
			(buf_info->rse_num - 1) * sizeof(fr_buf_ctl_t) -
			FR_MB_VECTOR + card->hw.dpmbase)
		;
		card->u.f.rx_base = buf_info->buf_base;
		card->u.f.rx_top  = buf_info->buf_top;
	}
	card->wandev.mtu	= conf->mtu;
	card->wandev.bps	= conf->bps;
	card->wandev.interface	= conf->interface;
	card->wandev.clocking	= conf->clocking;
	card->wandev.station	= conf->station;
	card->poll		= &wpf_poll;
	card->wandev.update	= &update;
	card->wandev.new_if	= &new_if;
	card->wandev.del_if	= &del_if;
	card->wandev.state	= WAN_DISCONNECTED;
	return 0;
}

/******* WAN Device Driver Entry Points *************************************/

/*============================================================================
 * Update device status & statistics.
 */
static int update (wan_device_t* wandev)
{
/*
	sdla_t* card = wandev->private;
*/
	return 0;
}

/*============================================================================
 * Create new logical channel.
 * This routine is called by the router when ROUTER_IFNEW IOCTL is being
 * handled.
 * o parse media- and hardware-specific configuration
 * o make sure that a new channel can be created
 * o allocate resources, if necessary
 * o prepare network device structure for registaration.
 *
 * Return:	0	o.k.
 *		< 0	failure (channel will not be created)
 */
static int new_if (wan_device_t* wandev, struct device* dev, wanif_conf_t* conf)
{
	sdla_t* card = wandev->private;
	fr_channel_t* chan;
	int err = 0;

	if ((conf->name[0] == '\0') || (strlen(conf->name) > WAN_IFNAME_SZ))
	{
		printk(KERN_INFO "%s: invalid interface name!\n",
			card->devname)
		;
		return -EINVAL;
	}

	/* allocate and initialize private data */
	chan = kmalloc(sizeof(fr_channel_t), GFP_KERNEL);
	if (chan == NULL)
		return -ENOMEM
	;
	memset(chan, 0, sizeof(fr_channel_t));
	strcpy(chan->name, conf->name);
	chan->card = card;

	/* verify media address */
	if (is_digit(conf->addr[0]))
	{
		int dlci = dec_to_uint(conf->addr, 0);

		if (dlci && (dlci <= 4095))
		{
			chan->dlci = dlci;
		}
		else
		{
			printk(KERN_ERR
				"%s: invalid DLCI %u on interface %s!\n",
				wandev->name, dlci, chan->name)
			;
			err = -EINVAL;
		}
	}
	else
	{
		printk(KERN_ERR
			"%s: invalid media address on interface %s!\n",
			wandev->name, chan->name)
		;
		err = -EINVAL;
	}
	if (err)
	{
		kfree(chan);
		return err;
	}

	/* prepare network device data space for registration */
	dev->name = chan->name;
	dev->init = &if_init;
	dev->priv = chan;
	return 0;
}

/*============================================================================
 * Delete logical channel.
 */
static int del_if (wan_device_t* wandev, struct device* dev)
{
	if (dev->priv)
	{
		kfree(dev->priv);
		dev->priv = NULL;
	}
	return 0;
}

/****** Network Device Interface ********************************************/

/*============================================================================
 * Initialize Linux network interface.
 *
 * This routine is called only once for each interface, during Linux network
 * interface registration.  Returning anything but zero will fail interface
 * registration.
 */
static int if_init (struct device* dev)
{
	fr_channel_t* chan = dev->priv;
	sdla_t* card = chan->card;
	wan_device_t* wandev = &card->wandev;
	int i;

	/* Initialize device driver entry points */
	dev->open		= &if_open;
	dev->stop		= &if_close;
	dev->hard_header	= &if_header;
	dev->rebuild_header	= &if_rebuild_hdr;
	dev->hard_start_xmit	= &if_send;
	dev->get_stats		= &if_stats;

	/* Initialize media-specific parameters */
	dev->family		= AF_INET;	/* address family */
	dev->type		= ARPHRD_DLCI;	/* ARP h/w type */
	dev->mtu		= FR_CHANNEL_MTU;
	dev->hard_header_len	= FR_HEADER_LEN;/* media header length */
	dev->addr_len		= 2;		/* hardware address length */
	*(unsigned short*)dev->dev_addr = htons(chan->dlci);

	/* Initialize hardware parameters (just for reference) */
	dev->irq	= wandev->irq;
	dev->dma	= wandev->dma;
	dev->base_addr	= wandev->ioport;
	dev->mem_start	= wandev->maddr;
	dev->mem_end	= wandev->maddr + wandev->msize - 1;

	/* Initialize socket buffers */
	for (i = 0; i < DEV_NUMBUFFS; ++i)
		skb_queue_head_init(&dev->buffs[i])
	;
	set_chan_state(dev, WAN_DISCONNECTED);
	return 0;
}

/*============================================================================
 * Open network interface.
 * o if this is the first open, then enable communications and interrupts.
 * o prevent module from unloading by incrementing use count
 *
 * Return 0 if O.k. or errno.
 */
static int if_open (struct device* dev)
{
	fr_channel_t* chan = dev->priv;
	sdla_t* card = chan->card;
	int err = 0;

	if (dev->start)
		return -EBUSY		/* only one open is allowed */
	;
	if (test_and_set_bit(0, (void*)&card->wandev.critical))
		return -EAGAIN;
	;
	if (!card->open_cnt)
	{
		if ((fr_comm_enable(card)) ||
		    (fr_set_intr_mode(card, 0x03, card->wandev.mtu)))
		{
			err = -EIO;
			goto done;
		}
		if (card->wandev.station == WANOPT_CPE)
		{
			/* CPE: issue full status enquiry */
			fr_issue_isf(card, FR_ISF_FSE);
		}
		else	/* Switch: activate DLCI(s) */
		{
			fr_add_dlci(card,
				card->u.f.node_dlci, card->u.f.dlci_num)
			;
			fr_activate_dlci(card,
				card->u.f.node_dlci, card->u.f.dlci_num)
			;
		}
		wanpipe_set_state(card, WAN_CONNECTED);
	}
	dev->mtu = min(dev->mtu, card->wandev.mtu - FR_HEADER_LEN);
	dev->interrupt = 0;
	dev->tbusy = 0;
	dev->start = 1;
	wanpipe_open(card);
	update_chan_state(dev);

done:
	card->wandev.critical = 0;
	return err;
}

/*============================================================================
 * Close network interface.
 * o if this is the last open, then disable communications and interrupts.
 * o reset flags.
 */
static int if_close (struct device* dev)
{
	fr_channel_t* chan = dev->priv;
	sdla_t* card = chan->card;

	if (test_and_set_bit(0, (void*)&card->wandev.critical))
		return -EAGAIN;
	;
	dev->start = 0;
	wanpipe_close(card);
	if (!card->open_cnt)
	{
		wanpipe_set_state(card, WAN_DISCONNECTED);
		fr_set_intr_mode(card, 0, 0);
		fr_comm_disable(card);
	}
	card->wandev.critical = 0;
	return 0;
}

/*============================================================================
 * Build media header.
 * o encapsulate packet according to encapsulation type.
 *
 * The trick here is to put packet type (Ethertype) into 'protocol' field of
 * the socket buffer, so that we don't forget it.  If encapsulation fails,
 * set skb->protocol to 0 and discard packet later.
 *
 * Return:	media header length.
 */
static int if_header (struct sk_buff* skb, struct device* dev,
	unsigned short type, void* daddr, void* saddr, unsigned len)
{
	int hdr_len = 0;

	skb->protocol = type;
	hdr_len = wan_encapsulate(skb, dev);
	if (hdr_len < 0)
	{
		hdr_len = 0;
		skb->protocol = 0;
	}
	skb_push(skb, 1);
	skb->data[0] = Q922_UI;
	++hdr_len;
	return hdr_len;
}

/*============================================================================
 * Re-build media header.
 *
 * Return:	1	physical address resolved.
 *		0	physical address not resolved
 */
static int if_rebuild_hdr (void* hdr, struct device* dev, unsigned long raddr,
			   struct sk_buff* skb)
{
	fr_channel_t* chan = dev->priv;
	sdla_t* card = chan->card;

	printk(KERN_INFO "%s: rebuild_header() called for interface %s!\n",
		card->devname, dev->name)
	;
	return 1;
}

/*============================================================================
 * Send a packet on a network interface.
 * o set tbusy flag (marks start of the transmission) to block a timer-based
 *   transmit from overlapping.
 * o check link state. If link is not up, then drop the packet.
 * o check channel status. If it's down then initiate a call.
 * o pass a packet to corresponding WAN device.
 * o free socket buffer
 *
 * Return:	0	complete (socket buffer must be freed)
 *		non-0	packet may be re-transmitted (tbusy must be set)
 *
 * Notes:
 * 1. This routine is called either by the protocol stack or by the "net
 *    bottom half" (with interrupts enabled).
 * 2. Setting tbusy flag will inhibit further transmit requests from the
 *    protocol stack and can be used for flow control with protocol layer.
 */
static int if_send (struct sk_buff* skb, struct device* dev)
{
	fr_channel_t* chan = dev->priv;
	sdla_t* card = chan->card;
	int retry = 0;

	if (test_and_set_bit(0, (void*)&card->wandev.critical))
	{
#ifdef _DEBUG_
		printk(KERN_INFO "%s: if_send() hit critical section!\n",
			card->devname)
		;
#endif
		return 1;
	}

	if (test_and_set_bit(0, (void*)&dev->tbusy))
	{
#ifdef _DEBUG_
		printk(KERN_INFO "%s: Tx collision on interface %s!\n",
			card->devname, dev->name)
		;
#endif
		++chan->ifstats.collisions;
		retry = 1;
	}
	else if ((card->wandev.state != WAN_CONNECTED) ||
	    (chan->state != WAN_CONNECTED))
		++chan->ifstats.tx_dropped
	;
	else if (!is_tx_ready(card))
		retry = 1
	;
	else
	{
 		int err = (card->hw.fwid == SFID_FR508) ?
			fr508_send(card, chan->dlci, 0, skb->len, skb->data) :
			fr502_send(card, chan->dlci, 0, skb->len, skb->data)
		;
		if (err) ++chan->ifstats.tx_errors;
		else ++chan->ifstats.tx_packets;
	}
	if (!retry)
	{
		dev_kfree_skb(skb, FREE_WRITE);
		dev->tbusy = 0;
	}
	card->wandev.critical = 0;
	return retry;
}

/*============================================================================
 * Get ethernet-style interface statistics.
 * Return a pointer to struct enet_statistics.
 */
static struct enet_statistics* if_stats (struct device* dev)
{
	fr_channel_t* chan = dev->priv;

	return &chan->ifstats;
}

/****** Interrupt Handlers **************************************************/

/*============================================================================
 * S502 frame relay interrupt service routine.
 */
static void fr502_isr (sdla_t* card)
{
	fr502_flags_t* flags = card->flags;

	switch (flags->iflag)
	{
	case 0x01:	/* receive interrupt */
		fr502_rx_intr(card);
		break;

	case 0x02:	/* transmit interrupt */
		flags->imask &= ~0x02;
		tx_intr(card);
		break;

	default:
		spur_intr(card);
	}
	flags->iflag = 0;
}

/*============================================================================
 * S508 frame relay interrupt service routine.
 */
static void fr508_isr (sdla_t* card)
{
	fr508_flags_t* flags = card->flags;
	fr_buf_ctl_t* bctl;

	switch (flags->iflag)
	{
	case 0x01:	/* receive interrupt */
		fr508_rx_intr(card);
		break;

	case 0x02:	/* transmit interrupt */
		bctl = (void*)(flags->tse_offs - FR_MB_VECTOR +
			card->hw.dpmbase)
		;
		bctl->flag = 0x90;	/* disable further Tx interrupts */
		tx_intr(card);
		break;

	default:
		spur_intr(card);
	}
	flags->iflag = 0;
}

/*============================================================================
 * Receive interrupt handler.
 */
static void fr502_rx_intr (sdla_t* card)
{
	fr_mbox_t* mbox = card->rxmb;
	struct sk_buff* skb;
	struct device* dev;
	fr_channel_t* chan;
	unsigned dlci, len;
	void* buf;

	sdla_mapmem(&card->hw, FR502_RX_VECTOR);
	dlci = mbox->cmd.dlci;
	len  = mbox->cmd.length;

	/* Find network interface for this packet */
	dev = find_channel(card, dlci);
	if (dev == NULL)
	{
		/* Invalid channel, discard packet */
		printk(KERN_INFO "%s: receiving on orphaned DLCI %d!\n",
			card->devname, dlci)
		;
		goto rx_done;
	}
	chan = dev->priv;
	if (!dev->start)
	{
		++chan->ifstats.rx_dropped;
		goto rx_done;
	}

	/* Allocate socket buffer */
	skb = dev_alloc_skb(len);
	if (skb == NULL)
	{
		printk(KERN_INFO "%s: no socket buffers available!\n",
			card->devname)
		;
		++chan->ifstats.rx_dropped;
		goto rx_done;
	}

	/* Copy data to the socket buffer */
	buf = skb_put(skb, len);
	memcpy(buf, mbox->data, len);
	sdla_mapmem(&card->hw, FR_MB_VECTOR);

	/* Decapsulate packet and pass it up the protocol stack */
	skb->dev = dev;
	buf = skb_pull(skb, 1);	/* remove hardware header */
	if (!wan_type_trans(skb, dev))
	{
		/* can't decapsulate packet */
		dev_kfree_skb(skb, FREE_READ);
		++chan->ifstats.rx_errors;
	}
	else
	{
		netif_rx(skb);
		++chan->ifstats.rx_packets;
	}

rx_done:
	sdla_mapmem(&card->hw, FR_MB_VECTOR);
}

/*============================================================================
 * Receive interrupt handler.
 */
static void fr508_rx_intr (sdla_t* card)
{
	fr_buf_ctl_t* frbuf = card->rxmb;
	struct sk_buff* skb;
	struct device* dev;
	fr_channel_t* chan;
	unsigned dlci, len, offs;
	void* buf;

	if (frbuf->flag != 0x01)
	{
		printk(KERN_INFO "%s: corrupted Rx buffer @ 0x%X!\n",
			card->devname, (unsigned)frbuf)
		;
		return;
	}
	len  = frbuf->length;
	dlci = frbuf->dlci;
	offs = frbuf->offset;

	/* Find network interface for this packet */
	dev = find_channel(card, dlci);
	if (dev == NULL)
	{
		/* Invalid channel, discard packet */
		printk(KERN_INFO "%s: receiving on orphaned DLCI %d!\n",
			card->devname, dlci)
		;
		goto rx_done;
	}
	chan = dev->priv;
	if (!dev->start)
	{
		++chan->ifstats.rx_dropped;
		goto rx_done;
	}

	/* Allocate socket buffer */
	skb = dev_alloc_skb(len);
	if (skb == NULL)
	{
		printk(KERN_INFO "%s: no socket buffers available!\n",
			card->devname)
		;
		++chan->ifstats.rx_dropped;
		goto rx_done;
	}

	/* Copy data to the socket buffer */
	if ((offs + len) > card->u.f.rx_top)
	{
		unsigned tmp = card->u.f.rx_top - offs;

		buf = skb_put(skb, tmp);
		sdla_peek(&card->hw, offs, buf, tmp);
		offs = card->u.f.rx_base;
		len -= tmp;
	}
	buf = skb_put(skb, len);
	sdla_peek(&card->hw, offs, buf, len);

	/* Decapsulate packet and pass it up the protocol stack */
	skb->dev = dev;
	buf = skb_pull(skb, 1);	/* remove hardware header */
	if (!wan_type_trans(skb, dev))
	{
		/* can't decapsulate packet */
		dev_kfree_skb(skb, FREE_READ);
		++chan->ifstats.rx_errors;
	}
	else
	{
		netif_rx(skb);
		++chan->ifstats.rx_packets;
	}

rx_done:
	/* Release buffer element and calculate a pointer to the next one */
	frbuf->flag = 0;
	card->rxmb = ++frbuf;
	if ((void*)frbuf > card->u.f.rxmb_last)
		card->rxmb = card->u.f.rxmb_base
	;
}

/*============================================================================
 * Transmit interrupt handler.
 * o print a warning
 * o 
 * If number of spurious interrupts exceeded some limit, then ???
 */
static void tx_intr (sdla_t* card)
{
	printk(KERN_INFO "%s: transmit interrupt!\n", card->devname);
}

/*============================================================================
 * Spurious interrupt handler.
 * o print a warning
 * o 
 * If number of spurious interrupts exceeded some limit, then ???
 */
static void spur_intr (sdla_t* card)
{
	printk(KERN_INFO "%s: spurious interrupt!\n", card->devname);
}

/****** Background Polling Routines  ****************************************/

/*============================================================================
 * Main polling routine.
 * This routine is repeatedly called by the WANPIPE 'thead' to allow for
 * time-dependent housekeeping work.
 *
 * o fetch asynchronous network events.
 *
 * Notes:
 * 1. This routine may be called on interrupt context with all interrupts
 *    enabled. Beware!
 */
static void wpf_poll (sdla_t* card)
{
	fr502_flags_t* flags = card->flags;

	if (flags->event)
	{
		fr_mbox_t* mbox = card->mbox;
		int err;

		memset(&mbox->cmd, 0, sizeof(fr_cmd_t));
		mbox->cmd.command = FR_READ_STATUS;
		err = sdla_exec(mbox) ? mbox->cmd.result : CMD_TIMEOUT;
		if (err) fr_event(card, err, mbox);
	}
}

/****** Frame Relay Firmware-Specific Functions *****************************/

/*============================================================================
 * Read firmware code version.
 * o fill string str with firmware version info. 
 */
static int fr_read_version (sdla_t* card, char* str)
{
	fr_mbox_t* mbox = card->mbox;
	int retry = MAX_CMD_RETRY;
	int err;

	do
	{
		memset(&mbox->cmd, 0, sizeof(fr_cmd_t));
		mbox->cmd.command = FR_READ_CODE_VERSION;
		err = sdla_exec(mbox) ? mbox->cmd.result : CMD_TIMEOUT;
	}
	while (err && retry-- && fr_event(card, err, mbox));
	if (!err && str)
	{
		int len = mbox->cmd.length;

		memcpy(str, mbox->data, len);
	        str[len] = '\0';
	}
	return err;
}

/*============================================================================
 * Set global configuration.
 */
static int fr_configure (sdla_t* card, fr_conf_t *conf)
{
	fr_mbox_t* mbox = card->mbox;
	int retry = MAX_CMD_RETRY;
	int dlci = card->u.f.node_dlci;
	int dlci_num = card->u.f.dlci_num;
	int err, i;

	do
	{
		memset(&mbox->cmd, 0, sizeof(fr_cmd_t));
		memcpy(mbox->data, conf, sizeof(fr_conf_t));
		if (dlci_num) for (i = 0; i < dlci_num; ++i)
			((fr_conf_t*)mbox->data)->dlci[i] = dlci + i
		;
		mbox->cmd.command = FR_SET_CONFIG;
		mbox->cmd.length =
			sizeof(fr_conf_t) + dlci_num * sizeof(short)
		;
		err = sdla_exec(mbox) ? mbox->cmd.result : CMD_TIMEOUT;
	}
	while (err && retry-- && fr_event(card, err, mbox));
	return err;
}

/*============================================================================
 * Set interrupt mode.
 */
static int fr_set_intr_mode (sdla_t* card, unsigned mode, unsigned mtu)
{
	fr_mbox_t* mbox = card->mbox;
	int retry = MAX_CMD_RETRY;
	int err;

	do
	{
		memset(&mbox->cmd, 0, sizeof(fr_cmd_t));
		if (card->hw.fwid == SFID_FR502)
		{
			fr502_intr_ctl_t* ictl = (void*)mbox->data;

			memset(ictl, 0, sizeof(fr502_intr_ctl_t));
			ictl->mode   = mode;
			ictl->tx_len = mtu;
			mbox->cmd.length = sizeof(fr502_intr_ctl_t);
		}
		else
		{
			fr508_intr_ctl_t* ictl = (void*)mbox->data;

			memset(ictl, 0, sizeof(fr508_intr_ctl_t));
			ictl->mode   = mode;
			ictl->tx_len = mtu;
			ictl->irq    = card->hw.irq;
			mbox->cmd.length = sizeof(fr508_intr_ctl_t);
		}
		mbox->cmd.command = FR_SET_INTR_MODE;
		err = sdla_exec(mbox) ? mbox->cmd.result : CMD_TIMEOUT;
	}
	while (err && retry-- && fr_event(card, err, mbox));
	return err;
}

/*============================================================================
 * Enable communications.
 */
static int fr_comm_enable (sdla_t* card)
{
	fr_mbox_t* mbox = card->mbox;
	int retry = MAX_CMD_RETRY;
	int err;

	do
	{
		memset(&mbox->cmd, 0, sizeof(fr_cmd_t));
		mbox->cmd.command = FR_COMM_ENABLE;
		err = sdla_exec(mbox) ? mbox->cmd.result : CMD_TIMEOUT;
	}
	while (err && retry-- && fr_event(card, err, mbox));
	return err;
}

/*============================================================================
 * Disable communications. 
 */
static int fr_comm_disable (sdla_t* card)
{
	fr_mbox_t* mbox = card->mbox;
	int retry = MAX_CMD_RETRY;
	int err;

	do
	{
		memset(&mbox->cmd, 0, sizeof(fr_cmd_t));
		mbox->cmd.command = FR_COMM_DISABLE;
		err = sdla_exec(mbox) ? mbox->cmd.result : CMD_TIMEOUT;
	}
	while (err && retry-- && fr_event(card, err, mbox));
	return err;
}

/*============================================================================
 * Add DLCI(s) (Access Node only!). 
 */
static int fr_add_dlci (sdla_t* card, int dlci, int num)
{
	fr_mbox_t* mbox = card->mbox;
	int retry = MAX_CMD_RETRY;
	int err, i;

	do
	{
		unsigned short* dlci_list = (void*)mbox->data;

		memset(&mbox->cmd, 0, sizeof(fr_cmd_t));
		for (i = 0; i < num; ++i)
			dlci_list[i] = dlci + i
		;
		mbox->cmd.length  = num * sizeof(short);
		mbox->cmd.command = FR_ADD_DLCI;
		err = sdla_exec(mbox) ? mbox->cmd.result : CMD_TIMEOUT;
	}
	while (err && retry-- && fr_event(card, err, mbox));
	return err;
}

/*============================================================================
 * Activate DLCI(s) (Access Node only!). 
 */
static int fr_activate_dlci (sdla_t* card, int dlci, int num)
{
	fr_mbox_t* mbox = card->mbox;
	int retry = MAX_CMD_RETRY;
	int err, i;

	do
	{
		unsigned short* dlci_list = (void*)mbox->data;

		memset(&mbox->cmd, 0, sizeof(fr_cmd_t));
		for (i = 0; i < num; ++i)
			dlci_list[i] = dlci + i
		;
		mbox->cmd.length  = num * sizeof(short);
		mbox->cmd.command = FR_ACTIVATE_DLCI;
		err = sdla_exec(mbox) ? mbox->cmd.result : CMD_TIMEOUT;
	}
	while (err && retry-- && fr_event(card, err, mbox));
	return err;
}

/*============================================================================
 * Issue in-channel signalling frame. 
 */
static int fr_issue_isf (sdla_t* card, int isf)
{
	fr_mbox_t* mbox = card->mbox;
	int retry = MAX_CMD_RETRY;
	int err;

	do
	{
		memset(&mbox->cmd, 0, sizeof(fr_cmd_t));
		mbox->data[0] = isf;
		mbox->cmd.length  = 1;
		mbox->cmd.command = FR_ISSUE_IS_FRAME;
		err = sdla_exec(mbox) ? mbox->cmd.result : CMD_TIMEOUT;
	}
	while (err && retry-- && fr_event(card, err, mbox));
	return err;
}

/*============================================================================
 * Send a frame (S502 version). 
 */
static int fr502_send (sdla_t* card, int dlci, int attr, int len, void *buf)
{
	fr_mbox_t* mbox = card->mbox;
	int retry = MAX_CMD_RETRY;
	int err;

	do
	{
		memset(&mbox->cmd, 0, sizeof(fr_cmd_t));
		memcpy(mbox->data, buf, len);
		mbox->cmd.dlci    = dlci;
		mbox->cmd.attr    = attr;
		mbox->cmd.length  = len;
		mbox->cmd.command = FR_WRITE;
		err = sdla_exec(mbox) ? mbox->cmd.result : CMD_TIMEOUT;
	}
	while (err && retry-- && fr_event(card, err, mbox));
	return err;
}

/*============================================================================
 * Send a frame (S508 version). 
 */
static int fr508_send (sdla_t* card, int dlci, int attr, int len, void *buf)
{
	fr_mbox_t* mbox = card->mbox;
	int retry = MAX_CMD_RETRY;
	int err;

	do
	{
		memset(&mbox->cmd, 0, sizeof(fr_cmd_t));
		mbox->cmd.dlci    = dlci;
		mbox->cmd.attr    = attr;
		mbox->cmd.length  = len;
		mbox->cmd.command = FR_WRITE;
		err = sdla_exec(mbox) ? mbox->cmd.result : CMD_TIMEOUT;
	}
	while (err && retry-- && fr_event(card, err, mbox));

	if (!err)
	{
		fr_buf_ctl_t* frbuf = (void*)(*(unsigned long*)mbox->data -
			FR_MB_VECTOR + card->hw.dpmbase)
		;
		unsigned long flags;

		save_flags(flags);
		cli();
		sdla_poke(&card->hw, frbuf->offset, buf, len);
		frbuf->flag = 0x01;
		restore_flags(flags);
	}
	return err;
}

/****** Firmware Asynchronous Event Handlers ********************************/

/*============================================================================
 * Main asyncronous event/error handler.
 *	This routine is called whenever firmware command returns non-zero
 *	return code.
 *
 * Return zero if previous command has to be cancelled.
 */
static int fr_event (sdla_t *card, int event, fr_mbox_t* mbox)
{
	switch (event)
	{
	case FRRES_MODEM_FAILURE:
		return fr_modem_failure(card, mbox);

	case FRRES_CHANNEL_DOWN:
		wanpipe_set_state(card, WAN_DISCONNECTED);
		return 1;

	case FRRES_CHANNEL_UP:
		wanpipe_set_state(card, WAN_CONNECTED);
		return 1;

	case FRRES_DLCI_CHANGE:
		return fr_dlci_change(card, mbox);

	case FRRES_DLCI_MISMATCH:
		printk(KERN_INFO "%s: DLCI list mismatch!\n", card->devname);
		return 1;

	case CMD_TIMEOUT:
		printk(KERN_ERR "%s: command 0x%02X timed out!\n",
			card->devname, mbox->cmd.command)
		;
		break;

	default:
		printk(KERN_INFO "%s: command 0x%02X returned 0x%02X!\n",
			card->devname, mbox->cmd.command, event)
		;
	}
	return 0;
}

/*============================================================================
 * Handle modem error.
 *
 * Return zero if previous command has to be cancelled.
 */
static int fr_modem_failure (sdla_t *card, fr_mbox_t* mbox)
{
	printk(KERN_INFO "%s: physical link down! (modem error 0x%02X)\n",
		card->devname, mbox->data[0])
	;
	switch (mbox->cmd.command)
	{
	case FR_WRITE:
	case FR_READ:
		return 0;
	}
	return 1;
}

/*============================================================================
 * Handle DLCI status change.
 *
 * Return zero if previous command has to be cancelled.
 */
static int fr_dlci_change (sdla_t *card, fr_mbox_t* mbox)
{
	dlci_status_t* status = (void*)mbox->data;
	int cnt = mbox->cmd.length / sizeof(dlci_status_t);

	for (; cnt; --cnt, ++status)
	{
		unsigned short dlci = status->dlci;
		struct device* dev = find_channel(card, dlci);

		if (status->state & 0x01)
		{
			printk(KERN_INFO
				"%s: DLCI %u has been deleted!\n",
				card->devname, dlci)
			;
			if (dev && dev->start)
				set_chan_state(dev, WAN_DISCONNECTED)
			;
		}
		else if (status->state & 0x02)
		{
			printk(KERN_INFO
				"%s: DLCI %u becomes active!\n",
				card->devname, dlci)
			;
			if (dev && dev->start)
				set_chan_state(dev, WAN_CONNECTED)
			;
		}
	}
	return 1;
}

/******* Miscellaneous ******************************************************/

/*============================================================================
 * Update channel state. 
 */
static int update_chan_state (struct device* dev)
{
	fr_channel_t* chan = dev->priv;
	sdla_t* card = chan->card;
	fr_mbox_t* mbox = card->mbox;
	int retry = MAX_CMD_RETRY;
	int err;

	do
	{
		memset(&mbox->cmd, 0, sizeof(fr_cmd_t));
		mbox->cmd.command = FR_LIST_ACTIVE_DLCI;
		err = sdla_exec(mbox) ? mbox->cmd.result : CMD_TIMEOUT;
	}
	while (err && retry-- && fr_event(card, err, mbox));

	if (!err)
	{
		unsigned short* list = (void*)mbox->data;
		int cnt = mbox->cmd.length / sizeof(short);

		for (; cnt; --cnt, ++list)
		{
			if (*list == chan->dlci)
			{
 				set_chan_state(dev, WAN_CONNECTED);
				break;
			}
		}
	}
	return err;
}

/*============================================================================
 * Set channel state.
 */
static void set_chan_state (struct device* dev, int state)
{
	fr_channel_t* chan = dev->priv;
	sdla_t* card = chan->card;
	unsigned long flags;

	save_flags(flags);
	cli();
	if (chan->state != state)
	{
		switch (state)
		{
		case WAN_CONNECTED:
			printk (KERN_INFO "%s: interface %s connected!\n",
				card->devname, dev->name)
			;
			break;

		case WAN_CONNECTING:
			printk (KERN_INFO "%s: interface %s connecting...\n",
				card->devname, dev->name)
			;
			break;

		case WAN_DISCONNECTED:
			printk (KERN_INFO "%s: interface %s disconnected!\n",
				card->devname, dev->name)
			;
			break;
		}
		chan->state = state;
	}
	chan->state_tick = jiffies;
	restore_flags(flags);
}

/*============================================================================
 * Find network device by its channel number.
 */
static struct device* find_channel (sdla_t* card, unsigned dlci)
{
	struct device* dev;

	for (dev = card->wandev.dev; dev; dev = dev->slave)
		if (((fr_channel_t*)dev->priv)->dlci == dlci) break
	;
	return dev;
}

/*============================================================================
 * Check to see if a frame can be sent. If no transmit buffers available,
 * enable transmit interrupts.
 *
 * Return:	1 - Tx buffer(s) available
 *		0 - no buffers available
 */
static int is_tx_ready (sdla_t* card)
{
	if (card->hw.fwid == SFID_FR508)
	{
		fr508_flags_t* flags = card->flags;
		unsigned char sb = inb(card->hw.port);

		if (sb & 0x02) return 1;
		flags->imask |= 0x02;
	}
	else
	{
		fr502_flags_t* flags = card->flags;

		if (flags->tx_ready) return 1;
		flags->imask |= 0x02;
	}
	return 0;
}

/*============================================================================
 * Convert decimal string to unsigned integer.
 * If len != 0 then only 'len' characters of the string are converted.
 */
static unsigned int dec_to_uint (unsigned char* str, int len)
{
	unsigned val;

	if (!len) len = strlen(str);
	for (val = 0; len && is_digit(*str); ++str, --len)
		val = (val * 10) + (*str - (unsigned)'0')
	;
	return val;
}

/*============================================================================
 * Convert hex string to unsigned integer.
 * If len != 0 then only 'len' characters of the string are conferted.
 */
static unsigned int hex_to_uint (unsigned char* str, int len)
{
	unsigned val, ch;

	if (!len) len = strlen(str);
	for (val = 0; len; ++str, --len)
	{
		ch = *str;
		if (is_digit(ch))
			val = (val << 4) + (ch - (unsigned)'0')
		;
		else if (is_hex_digit(ch))
			val = (val << 4) + ((ch & 0xDF) - (unsigned)'A' + 10)
		;
		else break;
	}
	return val;
}

/****** End *****************************************************************/