// SPDX-License-Identifier: GPL-2.0-only
/*
 *
 * Author	Karsten Keil <kkeil@novell.com>
 *
 * Copyright 2008  by Karsten Keil <kkeil@novell.com>
 */

#include <linux/gfp.h>
#include <linux/module.h>
#include <linux/mISDNhw.h>

static void
dchannel_bh(struct work_struct *ws)
{
	struct dchannel	*dch  = container_of(ws, struct dchannel, workq);
	struct sk_buff	*skb;
	int		err;

	if (test_and_clear_bit(FLG_RECVQUEUE, &dch->Flags)) {
		while ((skb = skb_dequeue(&dch->rqueue))) {
			if (likely(dch->dev.D.peer)) {
				err = dch->dev.D.recv(dch->dev.D.peer, skb);
				if (err)
					dev_kfree_skb(skb);
			} else
				dev_kfree_skb(skb);
		}
	}
	if (test_and_clear_bit(FLG_PHCHANGE, &dch->Flags)) {
		if (dch->phfunc)
			dch->phfunc(dch);
	}
}

static void
bchannel_bh(struct work_struct *ws)
{
	struct bchannel	*bch  = container_of(ws, struct bchannel, workq);
	struct sk_buff	*skb;
	int		err;

	if (test_and_clear_bit(FLG_RECVQUEUE, &bch->Flags)) {
		while ((skb = skb_dequeue(&bch->rqueue))) {
			bch->rcount--;
			if (likely(bch->ch.peer)) {
				err = bch->ch.recv(bch->ch.peer, skb);
				if (err)
					dev_kfree_skb(skb);
			} else
				dev_kfree_skb(skb);
		}
	}
}

int
mISDN_initdchannel(struct dchannel *ch, int maxlen, void *phf)
{
	test_and_set_bit(FLG_HDLC, &ch->Flags);
	ch->maxlen = maxlen;
	ch->hw = NULL;
	ch->rx_skb = NULL;
	ch->tx_skb = NULL;
	ch->tx_idx = 0;
	ch->phfunc = phf;
	skb_queue_head_init(&ch->squeue);
	skb_queue_head_init(&ch->rqueue);
	INIT_LIST_HEAD(&ch->dev.bchannels);
	INIT_WORK(&ch->workq, dchannel_bh);
	return 0;
}
EXPORT_SYMBOL(mISDN_initdchannel);

int
mISDN_initbchannel(struct bchannel *ch, unsigned short maxlen,
		   unsigned short minlen)
{
	ch->Flags = 0;
	ch->minlen = minlen;
	ch->next_minlen = minlen;
	ch->init_minlen = minlen;
	ch->maxlen = maxlen;
	ch->next_maxlen = maxlen;
	ch->init_maxlen = maxlen;
	ch->hw = NULL;
	ch->rx_skb = NULL;
	ch->tx_skb = NULL;
	ch->tx_idx = 0;
	skb_queue_head_init(&ch->rqueue);
	ch->rcount = 0;
	ch->next_skb = NULL;
	INIT_WORK(&ch->workq, bchannel_bh);
	return 0;
}
EXPORT_SYMBOL(mISDN_initbchannel);

int
mISDN_freedchannel(struct dchannel *ch)
{
	if (ch->tx_skb) {
		dev_kfree_skb(ch->tx_skb);
		ch->tx_skb = NULL;
	}
	if (ch->rx_skb) {
		dev_kfree_skb(ch->rx_skb);
		ch->rx_skb = NULL;
	}
	skb_queue_purge(&ch->squeue);
	skb_queue_purge(&ch->rqueue);
	flush_work(&ch->workq);
	return 0;
}
EXPORT_SYMBOL(mISDN_freedchannel);

void
mISDN_clear_bchannel(struct bchannel *ch)
{
	if (ch->tx_skb) {
		dev_kfree_skb(ch->tx_skb);
		ch->tx_skb = NULL;
	}
	ch->tx_idx = 0;
	if (ch->rx_skb) {
		dev_kfree_skb(ch->rx_skb);
		ch->rx_skb = NULL;
	}
	if (ch->next_skb) {
		dev_kfree_skb(ch->next_skb);
		ch->next_skb = NULL;
	}
	test_and_clear_bit(FLG_TX_BUSY, &ch->Flags);
	test_and_clear_bit(FLG_TX_NEXT, &ch->Flags);
	test_and_clear_bit(FLG_ACTIVE, &ch->Flags);
	test_and_clear_bit(FLG_FILLEMPTY, &ch->Flags);
	test_and_clear_bit(FLG_TX_EMPTY, &ch->Flags);
	test_and_clear_bit(FLG_RX_OFF, &ch->Flags);
	ch->dropcnt = 0;
	ch->minlen = ch->init_minlen;
	ch->next_minlen = ch->init_minlen;
	ch->maxlen = ch->init_maxlen;
	ch->next_maxlen = ch->init_maxlen;
	skb_queue_purge(&ch->rqueue);
	ch->rcount = 0;
}
EXPORT_SYMBOL(mISDN_clear_bchannel);

void
mISDN_freebchannel(struct bchannel *ch)
{
	cancel_work_sync(&ch->workq);
	mISDN_clear_bchannel(ch);
}
EXPORT_SYMBOL(mISDN_freebchannel);

int
mISDN_ctrl_bchannel(struct bchannel *bch, struct mISDN_ctrl_req *cq)
{
	int ret = 0;

	switch (cq->op) {
	case MISDN_CTRL_GETOP:
		cq->op = MISDN_CTRL_RX_BUFFER | MISDN_CTRL_FILL_EMPTY |
			 MISDN_CTRL_RX_OFF;
		break;
	case MISDN_CTRL_FILL_EMPTY:
		if (cq->p1) {
			memset(bch->fill, cq->p2 & 0xff, MISDN_BCH_FILL_SIZE);
			test_and_set_bit(FLG_FILLEMPTY, &bch->Flags);
		} else {
			test_and_clear_bit(FLG_FILLEMPTY, &bch->Flags);
		}
		break;
	case MISDN_CTRL_RX_OFF:
		/* read back dropped byte count */
		cq->p2 = bch->dropcnt;
		if (cq->p1)
			test_and_set_bit(FLG_RX_OFF, &bch->Flags);
		else
			test_and_clear_bit(FLG_RX_OFF, &bch->Flags);
		bch->dropcnt = 0;
		break;
	case MISDN_CTRL_RX_BUFFER:
		if (cq->p2 > MISDN_CTRL_RX_SIZE_IGNORE)
			bch->next_maxlen = cq->p2;
		if (cq->p1 > MISDN_CTRL_RX_SIZE_IGNORE)
			bch->next_minlen = cq->p1;
		/* we return the old values */
		cq->p1 = bch->minlen;
		cq->p2 = bch->maxlen;
		break;
	default:
		pr_info("mISDN unhandled control %x operation\n", cq->op);
		ret = -EINVAL;
		break;
	}
	return ret;
}
EXPORT_SYMBOL(mISDN_ctrl_bchannel);

static inline u_int
get_sapi_tei(u_char *p)
{
	u_int	sapi, tei;

	sapi = *p >> 2;
	tei = p[1] >> 1;
	return sapi | (tei << 8);
}

void
recv_Dchannel(struct dchannel *dch)
{
	struct mISDNhead *hh;

	if (dch->rx_skb->len < 2) { /* at least 2 for sapi / tei */
		dev_kfree_skb(dch->rx_skb);
		dch->rx_skb = NULL;
		return;
	}
	hh = mISDN_HEAD_P(dch->rx_skb);
	hh->prim = PH_DATA_IND;
	hh->id = get_sapi_tei(dch->rx_skb->data);
	skb_queue_tail(&dch->rqueue, dch->rx_skb);
	dch->rx_skb = NULL;
	schedule_event(dch, FLG_RECVQUEUE);
}
EXPORT_SYMBOL(recv_Dchannel);

void
recv_Echannel(struct dchannel *ech, struct dchannel *dch)
{
	struct mISDNhead *hh;

	if (ech->rx_skb->len < 2) { /* at least 2 for sapi / tei */
		dev_kfree_skb(ech->rx_skb);
		ech->rx_skb = NULL;
		return;
	}
	hh = mISDN_HEAD_P(ech->rx_skb);
	hh->prim = PH_DATA_E_IND;
	hh->id = get_sapi_tei(ech->rx_skb->data);
	skb_queue_tail(&dch->rqueue, ech->rx_skb);
	ech->rx_skb = NULL;
	schedule_event(dch, FLG_RECVQUEUE);
}
EXPORT_SYMBOL(recv_Echannel);

void
recv_Bchannel(struct bchannel *bch, unsigned int id, bool force)
{
	struct mISDNhead *hh;

	/* if allocation did fail upper functions still may call us */
	if (unlikely(!bch->rx_skb))
		return;
	if (unlikely(!bch->rx_skb->len)) {
		/* we have no data to send - this may happen after recovery
		 * from overflow or too small allocation.
		 * We need to free the buffer here */
		dev_kfree_skb(bch->rx_skb);
		bch->rx_skb = NULL;
	} else {
		if (test_bit(FLG_TRANSPARENT, &bch->Flags) &&
		    (bch->rx_skb->len < bch->minlen) && !force)
				return;
		hh = mISDN_HEAD_P(bch->rx_skb);
		hh->prim = PH_DATA_IND;
		hh->id = id;
		if (bch->rcount >= 64) {
			printk(KERN_WARNING
			       "B%d receive queue overflow - flushing!\n",
			       bch->nr);
			skb_queue_purge(&bch->rqueue);
		}
		bch->rcount++;
		skb_queue_tail(&bch->rqueue, bch->rx_skb);
		bch->rx_skb = NULL;
		schedule_event(bch, FLG_RECVQUEUE);
	}
}
EXPORT_SYMBOL(recv_Bchannel);

void
recv_Dchannel_skb(struct dchannel *dch, struct sk_buff *skb)
{
	skb_queue_tail(&dch->rqueue, skb);
	schedule_event(dch, FLG_RECVQUEUE);
}
EXPORT_SYMBOL(recv_Dchannel_skb);

void
recv_Bchannel_skb(struct bchannel *bch, struct sk_buff *skb)
{
	if (bch->rcount >= 64) {
		printk(KERN_WARNING "B-channel %p receive queue overflow, "
		       "flushing!\n", bch);
		skb_queue_purge(&bch->rqueue);
		bch->rcount = 0;
	}
	bch->rcount++;
	skb_queue_tail(&bch->rqueue, skb);
	schedule_event(bch, FLG_RECVQUEUE);
}
EXPORT_SYMBOL(recv_Bchannel_skb);

static void
confirm_Dsend(struct dchannel *dch)
{
	struct sk_buff	*skb;

	skb = _alloc_mISDN_skb(PH_DATA_CNF, mISDN_HEAD_ID(dch->tx_skb),
			       0, NULL, GFP_ATOMIC);
	if (!skb) {
		printk(KERN_ERR "%s: no skb id %x\n", __func__,
		       mISDN_HEAD_ID(dch->tx_skb));
		return;
	}
	skb_queue_tail(&dch->rqueue, skb);
	schedule_event(dch, FLG_RECVQUEUE);
}

int
get_next_dframe(struct dchannel *dch)
{
	dch->tx_idx = 0;
	dch->tx_skb = skb_dequeue(&dch->squeue);
	if (dch->tx_skb) {
		confirm_Dsend(dch);
		return 1;
	}
	dch->tx_skb = NULL;
	test_and_clear_bit(FLG_TX_BUSY, &dch->Flags);
	return 0;
}
EXPORT_SYMBOL(get_next_dframe);

static void
confirm_Bsend(struct bchannel *bch)
{
	struct sk_buff	*skb;

	if (bch->rcount >= 64) {
		printk(KERN_WARNING "B-channel %p receive queue overflow, "
		       "flushing!\n", bch);
		skb_queue_purge(&bch->rqueue);
		bch->rcount = 0;
	}
	skb = _alloc_mISDN_skb(PH_DATA_CNF, mISDN_HEAD_ID(bch->tx_skb),
			       0, NULL, GFP_ATOMIC);
	if (!skb) {
		printk(KERN_ERR "%s: no skb id %x\n", __func__,
		       mISDN_HEAD_ID(bch->tx_skb));
		return;
	}
	bch->rcount++;
	skb_queue_tail(&bch->rqueue, skb);
	schedule_event(bch, FLG_RECVQUEUE);
}

int
get_next_bframe(struct bchannel *bch)
{
	bch->tx_idx = 0;
	if (test_bit(FLG_TX_NEXT, &bch->Flags)) {
		bch->tx_skb = bch->next_skb;
		if (bch->tx_skb) {
			bch->next_skb = NULL;
			test_and_clear_bit(FLG_TX_NEXT, &bch->Flags);
			/* confirm imediately to allow next data */
			confirm_Bsend(bch);
			return 1;
		} else {
			test_and_clear_bit(FLG_TX_NEXT, &bch->Flags);
			printk(KERN_WARNING "B TX_NEXT without skb\n");
		}
	}
	bch->tx_skb = NULL;
	test_and_clear_bit(FLG_TX_BUSY, &bch->Flags);
	return 0;
}
EXPORT_SYMBOL(get_next_bframe);

void
queue_ch_frame(struct mISDNchannel *ch, u_int pr, int id, struct sk_buff *skb)
{
	struct mISDNhead *hh;

	if (!skb) {
		_queue_data(ch, pr, id, 0, NULL, GFP_ATOMIC);
	} else {
		if (ch->peer) {
			hh = mISDN_HEAD_P(skb);
			hh->prim = pr;
			hh->id = id;
			if (!ch->recv(ch->peer, skb))
				return;
		}
		dev_kfree_skb(skb);
	}
}
EXPORT_SYMBOL(queue_ch_frame);

int
dchannel_senddata(struct dchannel *ch, struct sk_buff *skb)
{
	/* check oversize */
	if (skb->len <= 0) {
		printk(KERN_WARNING "%s: skb too small\n", __func__);
		return -EINVAL;
	}
	if (skb->len > ch->maxlen) {
		printk(KERN_WARNING "%s: skb too large(%d/%d)\n",
		       __func__, skb->len, ch->maxlen);
		return -EINVAL;
	}
	/* HW lock must be obtained */
	if (test_and_set_bit(FLG_TX_BUSY, &ch->Flags)) {
		skb_queue_tail(&ch->squeue, skb);
		return 0;
	} else {
		/* write to fifo */
		ch->tx_skb = skb;
		ch->tx_idx = 0;
		return 1;
	}
}
EXPORT_SYMBOL(dchannel_senddata);

int
bchannel_senddata(struct bchannel *ch, struct sk_buff *skb)
{

	/* check oversize */
	if (skb->len <= 0) {
		printk(KERN_WARNING "%s: skb too small\n", __func__);
		return -EINVAL;
	}
	if (skb->len > ch->maxlen) {
		printk(KERN_WARNING "%s: skb too large(%d/%d)\n",
		       __func__, skb->len, ch->maxlen);
		return -EINVAL;
	}
	/* HW lock must be obtained */
	/* check for pending next_skb */
	if (ch->next_skb) {
		printk(KERN_WARNING
		       "%s: next_skb exist ERROR (skb->len=%d next_skb->len=%d)\n",
		       __func__, skb->len, ch->next_skb->len);
		return -EBUSY;
	}
	if (test_and_set_bit(FLG_TX_BUSY, &ch->Flags)) {
		test_and_set_bit(FLG_TX_NEXT, &ch->Flags);
		ch->next_skb = skb;
		return 0;
	} else {
		/* write to fifo */
		ch->tx_skb = skb;
		ch->tx_idx = 0;
		confirm_Bsend(ch);
		return 1;
	}
}
EXPORT_SYMBOL(bchannel_senddata);

/* The function allocates a new receive skb on demand with a size for the
 * requirements of the current protocol. It returns the tailroom of the
 * receive skb or an error.
 */
int
bchannel_get_rxbuf(struct bchannel *bch, int reqlen)
{
	int len;

	if (bch->rx_skb) {
		len = skb_tailroom(bch->rx_skb);
		if (len < reqlen) {
			pr_warn("B%d no space for %d (only %d) bytes\n",
				bch->nr, reqlen, len);
			if (test_bit(FLG_TRANSPARENT, &bch->Flags)) {
				/* send what we have now and try a new buffer */
				recv_Bchannel(bch, 0, true);
			} else {
				/* on HDLC we have to drop too big frames */
				return -EMSGSIZE;
			}
		} else {
			return len;
		}
	}
	/* update current min/max length first */
	if (unlikely(bch->maxlen != bch->next_maxlen))
		bch->maxlen = bch->next_maxlen;
	if (unlikely(bch->minlen != bch->next_minlen))
		bch->minlen = bch->next_minlen;
	if (unlikely(reqlen > bch->maxlen))
		return -EMSGSIZE;
	if (test_bit(FLG_TRANSPARENT, &bch->Flags)) {
		if (reqlen >= bch->minlen) {
			len = reqlen;
		} else {
			len = 2 * bch->minlen;
			if (len > bch->maxlen)
				len = bch->maxlen;
		}
	} else {
		/* with HDLC we do not know the length yet */
		len = bch->maxlen;
	}
	bch->rx_skb = mI_alloc_skb(len, GFP_ATOMIC);
	if (!bch->rx_skb) {
		pr_warn("B%d receive no memory for %d bytes\n", bch->nr, len);
		len = -ENOMEM;
	}
	return len;
}
EXPORT_SYMBOL(bchannel_get_rxbuf);