// 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);