/* $Id: isdn_v110.c,v 1.1.2.2 2004/01/12 22:37:19 keil Exp $
 *
 * Linux ISDN subsystem, V.110 related functions (linklevel).
 *
 * Copyright by Thomas Pfeiffer (pfeiffer@pds.de)
 *
 * This software may be used and distributed according to the terms
 * of the GNU General Public License, incorporated herein by reference.
 *
 */

#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/delay.h>

#include <linux/isdn.h>
#include "isdn_v110.h"

#undef ISDN_V110_DEBUG

char *isdn_v110_revision = "$Revision: 1.1.2.2 $";

#define V110_38400 255
#define V110_19200  15
#define V110_9600    3

/* 
 * The following data are precoded matrices, online and offline matrix 
 * for 9600, 19200 und 38400, respectively
 */
static unsigned char V110_OnMatrix_9600[] =
{0xfc, 0xfc, 0xfc, 0xfc, 0xff, 0xff, 0xff, 0xfd, 0xff, 0xff,
 0xff, 0xfd, 0xff, 0xff, 0xff, 0xfd, 0xff, 0xff, 0xff, 0xfd,
 0xfd, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xfd, 0xff, 0xff,
 0xff, 0xfd, 0xff, 0xff, 0xff, 0xfd, 0xff, 0xff, 0xff, 0xfd};

static unsigned char V110_OffMatrix_9600[] =
{0xfc, 0xfc, 0xfc, 0xfc, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
 0xfd, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff};

static unsigned char V110_OnMatrix_19200[] =
{0xf0, 0xf0, 0xff, 0xf7, 0xff, 0xf7, 0xff, 0xf7, 0xff, 0xf7,
 0xfd, 0xff, 0xff, 0xf7, 0xff, 0xf7, 0xff, 0xf7, 0xff, 0xf7};

static unsigned char V110_OffMatrix_19200[] =
{0xf0, 0xf0, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
 0xfd, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff};

static unsigned char V110_OnMatrix_38400[] =
{0x00, 0x7f, 0x7f, 0x7f, 0x7f, 0xfd, 0x7f, 0x7f, 0x7f, 0x7f};

static unsigned char V110_OffMatrix_38400[] =
{0x00, 0xff, 0xff, 0xff, 0xff, 0xfd, 0xff, 0xff, 0xff, 0xff};

/* 
 * FlipBits reorders sequences of keylen bits in one byte.
 * E.g. source order 7654321 will be converted to 45670123 when keylen = 4,
 * and to 67452301 when keylen = 2. This is necessary because ordering on
 * the isdn line is the other way.
 */
static inline unsigned char
FlipBits(unsigned char c, int keylen)
{
        unsigned char b = c;
        unsigned char bit = 128;
        int i;
        int j;
        int hunks = (8 / keylen);

        c = 0;
        for (i = 0; i < hunks; i++) {
                for (j = 0; j < keylen; j++) {
                        if (b & (bit >> j))
                                c |= bit >> (keylen - j - 1);
                }
                bit >>= keylen;
        }
        return c;
}


/* isdn_v110_open allocates and initializes private V.110 data
 * structures and returns a pointer to these.
 */
static isdn_v110_stream *
isdn_v110_open(unsigned char key, int hdrlen, int maxsize)
{
        int i;
        isdn_v110_stream *v;

        if ((v = kzalloc(sizeof(isdn_v110_stream), GFP_ATOMIC)) == NULL)
                return NULL;
        v->key = key;
        v->nbits = 0;
        for (i = 0; key & (1 << i); i++)
                v->nbits++;

        v->nbytes = 8 / v->nbits;
        v->decodelen = 0;

        switch (key) {
                case V110_38400:
                        v->OnlineFrame = V110_OnMatrix_38400;
                        v->OfflineFrame = V110_OffMatrix_38400;
                        break;
                case V110_19200:
                        v->OnlineFrame = V110_OnMatrix_19200;
                        v->OfflineFrame = V110_OffMatrix_19200;
                        break;
                default:
                        v->OnlineFrame = V110_OnMatrix_9600;
                        v->OfflineFrame = V110_OffMatrix_9600;
                        break;
        }
        v->framelen = v->nbytes * 10;
        v->SyncInit = 5;
        v->introducer = 0;
        v->dbit = 1;
        v->b = 0;
        v->skbres = hdrlen;
        v->maxsize = maxsize - hdrlen;
        if ((v->encodebuf = kmalloc(maxsize, GFP_ATOMIC)) == NULL) {
                kfree(v);
                return NULL;
        }
        return v;
}

/* isdn_v110_close frees private V.110 data structures */
void
isdn_v110_close(isdn_v110_stream * v)
{
        if (v == NULL)
                return;
#ifdef ISDN_V110_DEBUG
        printk(KERN_DEBUG "v110 close\n");
#endif
        kfree(v->encodebuf);
        kfree(v);
}


/* 
 * ValidHeaderBytes return the number of valid bytes in v->decodebuf 
 */
static int
ValidHeaderBytes(isdn_v110_stream * v)
{
        int i;
        for (i = 0; (i < v->decodelen) && (i < v->nbytes); i++)
                if ((v->decodebuf[i] & v->key) != 0)
                        break;
        return i;
}

/* 
 * SyncHeader moves the decodebuf ptr to the next valid header 
 */
static void
SyncHeader(isdn_v110_stream * v)
{
        unsigned char *rbuf = v->decodebuf;
        int len = v->decodelen;

        if (len == 0)
                return;
        for (rbuf++, len--; len > 0; len--, rbuf++)     /* such den SyncHeader in buf ! */
                if ((*rbuf & v->key) == 0)      /* erstes byte gefunden ?       */
                        break;  /* jupp!                        */
        if (len)
                memcpy(v->decodebuf, rbuf, len);

        v->decodelen = len;
#ifdef ISDN_V110_DEBUG
        printk(KERN_DEBUG "isdn_v110: Header resync\n");
#endif
}

/* DecodeMatrix takes n (n>=1) matrices (v110 frames, 10 bytes) where
   len is the number of matrix-lines. len must be a multiple of 10, i.e.
   only complete matices must be given.
   From these, netto data is extracted and returned in buf. The return-value
   is the bytecount of the decoded data.
 */
static int
DecodeMatrix(isdn_v110_stream * v, unsigned char *m, int len, unsigned char *buf)
{
        int line = 0;
        int buflen = 0;
        int mbit = 64;
        int introducer = v->introducer;
        int dbit = v->dbit;
        unsigned char b = v->b;

        while (line < len) {    /* Are we done with all lines of the matrix? */
                if ((line % 10) == 0) { /* the 0. line of the matrix is always 0 ! */
                        if (m[line] != 0x00) {  /* not 0 ? -> error! */
#ifdef ISDN_V110_DEBUG
                                printk(KERN_DEBUG "isdn_v110: DecodeMatrix, V110 Bad Header\n");
                                /* returning now is not the right thing, though :-( */
#endif
                        } 
                        line++; /* next line of matrix */
                        continue;
                } else if ((line % 10) == 5) {  /* in line 5 there's only e-bits ! */
                        if ((m[line] & 0x70) != 0x30) { /* 011 has to be at the beginning! */
#ifdef ISDN_V110_DEBUG
                                printk(KERN_DEBUG "isdn_v110: DecodeMatrix, V110 Bad 5th line\n");
                                /* returning now is not the right thing, though :-( */
#endif
                        }
                        line++; /* next line */
                        continue;
                } else if (!introducer) {       /* every byte starts with 10 (stopbit, startbit) */
                        introducer = (m[line] & mbit) ? 0 : 1;  /* current bit of the matrix */
                      next_byte:
                        if (mbit > 2) { /* was it the last bit in this line ? */
                                mbit >>= 1;     /* no -> take next */
                                continue;
                        }       /* otherwise start with leftmost bit in the next line */
                        mbit = 64;
                        line++;
                        continue;
                } else {        /* otherwise we need to set a data bit */
                        if (m[line] & mbit)     /* was that bit set in the matrix ? */
                                b |= dbit;      /* yes -> set it in the data byte */
                        else
                                b &= dbit - 1;  /* no -> clear it in the data byte */
                        if (dbit < 128) /* is that data byte done ? */
                                dbit <<= 1;     /* no, got the next bit */
                        else {  /* data byte is done */
                                buf[buflen++] = b;      /* copy byte into the output buffer */
                                introducer = b = 0;     /* init of the intro sequence and of the data byte */
                                dbit = 1;       /* next we look for the 0th bit */
                        }
                        goto next_byte; /* look for next bit in the matrix */
                }
        }
        v->introducer = introducer;
        v->dbit = dbit;
        v->b = b;
        return buflen;          /* return number of bytes in the output buffer */
}

/* 
 * DecodeStream receives V.110 coded data from the input stream. It recovers the 
 * original frames.
 * The input stream doesn't need to be framed
 */
struct sk_buff *
isdn_v110_decode(isdn_v110_stream * v, struct sk_buff *skb)
{
        int i;
        int j;
        int len;
        unsigned char *v110_buf;
        unsigned char *rbuf;

        if (!skb) {
                printk(KERN_WARNING "isdn_v110_decode called with NULL skb!\n");
                return NULL;
        }
        rbuf = skb->data;
        len = skb->len;
        if (v == NULL) {
                /* invalid handle, no chance to proceed */
                printk(KERN_WARNING "isdn_v110_decode called with NULL stream!\n");
                dev_kfree_skb(skb);
                return NULL;
        }
        if (v->decodelen == 0)  /* cache empty?               */
                for (; len > 0; len--, rbuf++)  /* scan for SyncHeader in buf */
                        if ((*rbuf & v->key) == 0)
                                break;  /* found first byte           */
        if (len == 0) {
                dev_kfree_skb(skb);
                return NULL;
        }
        /* copy new data to decode-buffer */
        memcpy(&(v->decodebuf[v->decodelen]), rbuf, len);
        v->decodelen += len;
      ReSync:
        if (v->decodelen < v->nbytes) { /* got a new header ? */
                dev_kfree_skb(skb);
                return NULL;    /* no, try later      */
        }
        if (ValidHeaderBytes(v) != v->nbytes) { /* is that a valid header? */
                SyncHeader(v);  /* no -> look for header */
                goto ReSync;
        }
        len = (v->decodelen - (v->decodelen % (10 * v->nbytes))) / v->nbytes;
        if ((v110_buf = kmalloc(len, GFP_ATOMIC)) == NULL) {
                printk(KERN_WARNING "isdn_v110_decode: Couldn't allocate v110_buf\n");
                dev_kfree_skb(skb);
                return NULL;
        }
        for (i = 0; i < len; i++) {
                v110_buf[i] = 0;
                for (j = 0; j < v->nbytes; j++)
                        v110_buf[i] |= (v->decodebuf[(i * v->nbytes) + j] & v->key) << (8 - ((j + 1) * v->nbits));
                v110_buf[i] = FlipBits(v110_buf[i], v->nbits);
        }
        v->decodelen = (v->decodelen % (10 * v->nbytes));
        memcpy(v->decodebuf, &(v->decodebuf[len * v->nbytes]), v->decodelen);

        skb_trim(skb, DecodeMatrix(v, v110_buf, len, skb->data));
        kfree(v110_buf);
        if (skb->len)
                return skb;
        else {
                kfree_skb(skb);
                return NULL;
        }
}

/* EncodeMatrix takes input data in buf, len is the bytecount.
   Data is encoded into v110 frames in m. Return value is the number of
   matrix-lines generated.
 */
static int
EncodeMatrix(unsigned char *buf, int len, unsigned char *m, int mlen)
{
        int line = 0;
        int i = 0;
        int mbit = 128;
        int dbit = 1;
        int introducer = 3;
        int ibit[] = {0, 1, 1};

        while ((i < len) && (line < mlen)) {    /* while we still have input data */
                switch (line % 10) {    /* in which line of the matrix are we? */
                        case 0:
                                m[line++] = 0x00;       /* line 0 is always 0 */
                                mbit = 128;     /* go on with the 7th bit */
                                break;
                        case 5:
                                m[line++] = 0xbf;       /* line 5 is always 10111111 */
                                mbit = 128;     /* go on with the 7th bit */
                                break;
                }
                if (line >= mlen) {
                        printk(KERN_WARNING "isdn_v110 (EncodeMatrix): buffer full!\n");
                        return line;
                }
        next_bit:
                switch (mbit) { /* leftmost or rightmost bit ? */
                        case 1:
                                line++; /* rightmost -> go to next line */
                                if (line >= mlen) {
                                        printk(KERN_WARNING "isdn_v110 (EncodeMatrix): buffer full!\n");
                                        return line;
                                }
                        case 128:
                                m[line] = 128;  /* leftmost -> set byte to 1000000 */
                                mbit = 64;      /* current bit in the matrix line */
                                continue;
                }
                if (introducer) {       /* set 110 sequence ? */
                        introducer--;   /* set on digit less */
                        m[line] |= ibit[introducer] ? mbit : 0; /* set corresponding bit */
                        mbit >>= 1;     /* bit of matrix line  >> 1 */
                        goto next_bit;  /* and go on there */
                }               /* else push data bits into the matrix! */
                m[line] |= (buf[i] & dbit) ? mbit : 0;  /* set data bit in matrix */
                if (dbit == 128) {      /* was it the last one? */
                        dbit = 1;       /* then go on with first bit of  */
                        i++;            /* next byte in input buffer */
                        if (i < len)    /* input buffer done ? */
                                introducer = 3; /* no, write introducer 110 */
                        else {  /* input buffer done ! */
                                m[line] |= (mbit - 1) & 0xfe;   /* set remaining bits in line to 1 */
                                break;
                        }
                } else          /* not the last data bit */
                        dbit <<= 1;     /* then go to next data bit */
                mbit >>= 1;     /* go to next bit of matrix */
                goto next_bit;

        }
        /* if necessary, generate remaining lines of the matrix... */
        if ((line) && ((line + 10) < mlen))
                switch (++line % 10) {
                        case 1:
                                m[line++] = 0xfe;
                        case 2:
                                m[line++] = 0xfe;
                        case 3:
                                m[line++] = 0xfe;
                        case 4:
                                m[line++] = 0xfe;
                        case 5:
                                m[line++] = 0xbf;
                        case 6:
                                m[line++] = 0xfe;
                        case 7:
                                m[line++] = 0xfe;
                        case 8:
                                m[line++] = 0xfe;
                        case 9:
                                m[line++] = 0xfe;
                }
        return line;            /* that's how many lines we have */
}

/*
 * Build a sync frame.
 */
static struct sk_buff *
isdn_v110_sync(isdn_v110_stream *v)
{
        struct sk_buff *skb;

        if (v == NULL) {
                /* invalid handle, no chance to proceed */
                printk(KERN_WARNING "isdn_v110_sync called with NULL stream!\n");
                return NULL;
        }
        if ((skb = dev_alloc_skb(v->framelen + v->skbres))) {
                skb_reserve(skb, v->skbres);
                memcpy(skb_put(skb, v->framelen), v->OfflineFrame, v->framelen);
        }
        return skb;
}

/*
 * Build an idle frame.
 */
static struct sk_buff *
isdn_v110_idle(isdn_v110_stream *v)
{
        struct sk_buff *skb;

        if (v == NULL) {
                /* invalid handle, no chance to proceed */
                printk(KERN_WARNING "isdn_v110_sync called with NULL stream!\n");
                return NULL;
        }
        if ((skb = dev_alloc_skb(v->framelen + v->skbres))) {
                skb_reserve(skb, v->skbres);
                memcpy(skb_put(skb, v->framelen), v->OnlineFrame, v->framelen);
        }
        return skb;
}

struct sk_buff *
isdn_v110_encode(isdn_v110_stream * v, struct sk_buff *skb)
{
        int i;
        int j;
        int rlen;
        int mlen;
        int olen;
        int size;
        int sval1;
        int sval2;
        int nframes;
        unsigned char *v110buf;
        unsigned char *rbuf;
        struct sk_buff *nskb;

        if (v == NULL) {
                /* invalid handle, no chance to proceed */
                printk(KERN_WARNING "isdn_v110_encode called with NULL stream!\n");
                return NULL;
        }
        if (!skb) {
                /* invalid skb, no chance to proceed */
                printk(KERN_WARNING "isdn_v110_encode called with NULL skb!\n");
                return NULL;
        }
        rlen = skb->len;
        nframes = (rlen + 3) / 4;
        v110buf = v->encodebuf;
        if ((nframes * 40) > v->maxsize) {
                size = v->maxsize;
                rlen = v->maxsize / 40;
        } else
                size = nframes * 40;
        if (!(nskb = dev_alloc_skb(size + v->skbres + sizeof(int)))) {
                printk(KERN_WARNING "isdn_v110_encode: Couldn't alloc skb\n");
                return NULL;
        }
        skb_reserve(nskb, v->skbres + sizeof(int));
        if (skb->len == 0) {
                memcpy(skb_put(nskb, v->framelen), v->OnlineFrame, v->framelen);
                *((int *)skb_push(nskb, sizeof(int))) = 0;
                return nskb;
        }
        mlen = EncodeMatrix(skb->data, rlen, v110buf, size);
        /* now distribute 2 or 4 bits each to the output stream! */
        rbuf = skb_put(nskb, size);
        olen = 0;
        sval1 = 8 - v->nbits;
        sval2 = v->key << sval1;
        for (i = 0; i < mlen; i++) {
                v110buf[i] = FlipBits(v110buf[i], v->nbits);
                for (j = 0; j < v->nbytes; j++) {
                        if (size--)
                                *rbuf++ = ~v->key | (((v110buf[i] << (j * v->nbits)) & sval2) >> sval1);
                        else {
                                printk(KERN_WARNING "isdn_v110_encode: buffers full!\n");
                                goto buffer_full;
                        }
                        olen++;
                }
        }
buffer_full:
        skb_trim(nskb, olen);
        *((int *)skb_push(nskb, sizeof(int))) = rlen;
        return nskb;
}

int
isdn_v110_stat_callback(int idx, isdn_ctrl *c)
{
        isdn_v110_stream *v = NULL;
        int i;
        int ret = 0;

        if (idx < 0)
                return 0;
        switch (c->command) {
                case ISDN_STAT_BSENT:
                        /* Keep the send-queue of the driver filled
                         * with frames:
                         * If number of outstanding frames < 3,
                         * send down an Idle-Frame (or an Sync-Frame, if
                         * v->SyncInit != 0). 
                         */
                        if (!(v = dev->v110[idx]))
                                return 0;
                        atomic_inc(&dev->v110use[idx]);
                        for (i=0; i * v->framelen < c->parm.length; i++) {
                                if (v->skbidle > 0) {
                                        v->skbidle--;
                                        ret = 1;
                                } else {
                                        if (v->skbuser > 0)
                                                v->skbuser--;
                                        ret = 0;
                                }
                        }
                        for (i = v->skbuser + v->skbidle; i < 2; i++) {
                                struct sk_buff *skb;
                                if (v->SyncInit > 0)
                                        skb = isdn_v110_sync(v);
                                else
                                        skb = isdn_v110_idle(v);
                                if (skb) {
                                        if (dev->drv[c->driver]->interface->writebuf_skb(c->driver, c->arg, 1, skb) <= 0) {
                                                dev_kfree_skb(skb);
                                                break;
                                        } else {
                                                if (v->SyncInit)
                                                        v->SyncInit--;
                                                v->skbidle++;
                                        }
                                } else
                                        break;
                        }
                        atomic_dec(&dev->v110use[idx]);
                        return ret;
                case ISDN_STAT_DHUP:
                case ISDN_STAT_BHUP:
                        while (1) {
                                atomic_inc(&dev->v110use[idx]);
                                if (atomic_dec_and_test(&dev->v110use[idx])) {
                                        isdn_v110_close(dev->v110[idx]);
                                        dev->v110[idx] = NULL;
                                        break;
                                }
                                mdelay(1);
                        }
                        break;
                case ISDN_STAT_BCONN:
                        if (dev->v110emu[idx] && (dev->v110[idx] == NULL)) {
                                int hdrlen = dev->drv[c->driver]->interface->hl_hdrlen;
                                int maxsize = dev->drv[c->driver]->interface->maxbufsize;
                                atomic_inc(&dev->v110use[idx]);
                                switch (dev->v110emu[idx]) {
                                        case ISDN_PROTO_L2_V11096:
                                                dev->v110[idx] = isdn_v110_open(V110_9600, hdrlen, maxsize);
                                                break;
                                        case ISDN_PROTO_L2_V11019:
                                                dev->v110[idx] = isdn_v110_open(V110_19200, hdrlen, maxsize);
                                                break;
                                        case ISDN_PROTO_L2_V11038:
                                                dev->v110[idx] = isdn_v110_open(V110_38400, hdrlen, maxsize);
                                                break;
                                        default:;
                                }
                                if ((v = dev->v110[idx])) {
                                        while (v->SyncInit) {
                                                struct sk_buff *skb = isdn_v110_sync(v);
                                                if (dev->drv[c->driver]->interface->writebuf_skb(c->driver, c->arg, 1, skb) <= 0) {
                                                        dev_kfree_skb(skb);
                                                        /* Unable to send, try later */
                                                        break;
                                                }
                                                v->SyncInit--;
                                                v->skbidle++;
                                        }
                                } else
                                        printk(KERN_WARNING "isdn_v110: Couldn't open stream for chan %d\n", idx);
                                atomic_dec(&dev->v110use[idx]);
                        }
                        break;
                default:
                        return 0;
        }
        return 0;
}