dvb_ringbuffer.c

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/*
 *
 * dvb_ringbuffer.c: ring buffer implementation for the dvb driver
 *
 * Copyright (C) 2003 Oliver Endriss
 * Copyright (C) 2004 Andrew de Quincey
 *
 * based on code originally found in av7110.c & dvb_ci.c:
 * Copyright (C) 1999-2003 Ralph  Metzler
 *                       & Marcus Metzler for convergence integrated media GmbH
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public License
 * as published by the Free Software Foundation; either version 2.1
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */



#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/string.h>
#include <asm/uaccess.h>

#include "dvb_ringbuffer.h"

#define PKT_READY 0
#define PKT_DISPOSED 1


void dvb_ringbuffer_init(struct dvb_ringbuffer *rbuf, void *data, size_t len)
{
    rbuf->pread=rbuf->pwrite=0;
    rbuf->data=data;
    rbuf->size=len;
    rbuf->error=0;

    init_waitqueue_head(&rbuf->queue);

    spin_lock_init(&(rbuf->lock));
}



int dvb_ringbuffer_empty(struct dvb_ringbuffer *rbuf)
{
    return (rbuf->pread==rbuf->pwrite);
}



ssize_t dvb_ringbuffer_free(struct dvb_ringbuffer *rbuf)
{
    ssize_t free;

    free = rbuf->pread - rbuf->pwrite;
    if (free <= 0)
        free += rbuf->size;
    return free-1;
}



ssize_t dvb_ringbuffer_avail(struct dvb_ringbuffer *rbuf)
{
    ssize_t avail;

    avail = rbuf->pwrite - rbuf->pread;
    if (avail < 0)
        avail += rbuf->size;
    return avail;
}



void dvb_ringbuffer_flush(struct dvb_ringbuffer *rbuf)
{
    rbuf->pread = rbuf->pwrite;
    rbuf->error = 0;
}
EXPORT_SYMBOL(dvb_ringbuffer_flush);

void dvb_ringbuffer_reset(struct dvb_ringbuffer *rbuf)
{
    rbuf->pread = rbuf->pwrite = 0;
    rbuf->error = 0;
}

void dvb_ringbuffer_flush_spinlock_wakeup(struct dvb_ringbuffer *rbuf)
{
    unsigned long flags;

    spin_lock_irqsave(&rbuf->lock, flags);
    dvb_ringbuffer_flush(rbuf);
    spin_unlock_irqrestore(&rbuf->lock, flags);

    wake_up(&rbuf->queue);
}

ssize_t dvb_ringbuffer_read_user(struct dvb_ringbuffer *rbuf, u8 __user *buf, size_t len)
{
    size_t todo = len;
    size_t split;

    split = (rbuf->pread + len > rbuf->size) ? rbuf->size - rbuf->pread : 0;
    if (split > 0) {
        if (copy_to_user(buf, rbuf->data+rbuf->pread, split))
            return -EFAULT;
        buf += split;
        todo -= split;
        rbuf->pread = 0;
    }
    if (copy_to_user(buf, rbuf->data+rbuf->pread, todo))
        return -EFAULT;

    rbuf->pread = (rbuf->pread + todo) % rbuf->size;

    return len;
}

void dvb_ringbuffer_read(struct dvb_ringbuffer *rbuf, u8 *buf, size_t len)
{
    size_t todo = len;
    size_t split;

    split = (rbuf->pread + len > rbuf->size) ? rbuf->size - rbuf->pread : 0;
    if (split > 0) {
        memcpy(buf, rbuf->data+rbuf->pread, split);
        buf += split;
        todo -= split;
        rbuf->pread = 0;
    }
    memcpy(buf, rbuf->data+rbuf->pread, todo);

    rbuf->pread = (rbuf->pread + todo) % rbuf->size;
}


ssize_t dvb_ringbuffer_write(struct dvb_ringbuffer *rbuf, const u8 *buf, size_t len)
{
    size_t todo = len;
    size_t split;

    split = (rbuf->pwrite + len > rbuf->size) ? rbuf->size - rbuf->pwrite : 0;

    if (split > 0) {
        memcpy(rbuf->data+rbuf->pwrite, buf, split);
        buf += split;
        todo -= split;
        rbuf->pwrite = 0;
    }
    memcpy(rbuf->data+rbuf->pwrite, buf, todo);
    rbuf->pwrite = (rbuf->pwrite + todo) % rbuf->size;

    return len;
}

ssize_t dvb_ringbuffer_pkt_write(struct dvb_ringbuffer *rbuf, u8* buf, size_t len)
{
    int status;
    ssize_t oldpwrite = rbuf->pwrite;

    DVB_RINGBUFFER_WRITE_BYTE(rbuf, len >> 8);
    DVB_RINGBUFFER_WRITE_BYTE(rbuf, len & 0xff);
    DVB_RINGBUFFER_WRITE_BYTE(rbuf, PKT_READY);
    status = dvb_ringbuffer_write(rbuf, buf, len);

    if (status < 0) rbuf->pwrite = oldpwrite;
    return status;
}

ssize_t dvb_ringbuffer_pkt_read_user(struct dvb_ringbuffer *rbuf, size_t idx,
                int offset, u8 __user *buf, size_t len)
{
    size_t todo;
    size_t split;
    size_t pktlen;

    pktlen = rbuf->data[idx] << 8;
    pktlen |= rbuf->data[(idx + 1) % rbuf->size];
    if (offset > pktlen) return -EINVAL;
    if ((offset + len) > pktlen) len = pktlen - offset;

    idx = (idx + DVB_RINGBUFFER_PKTHDRSIZE + offset) % rbuf->size;
    todo = len;
    split = ((idx + len) > rbuf->size) ? rbuf->size - idx : 0;
    if (split > 0) {
        if (copy_to_user(buf, rbuf->data+idx, split))
            return -EFAULT;
        buf += split;
        todo -= split;
        idx = 0;
    }
    if (copy_to_user(buf, rbuf->data+idx, todo))
        return -EFAULT;

    return len;
}

ssize_t dvb_ringbuffer_pkt_read(struct dvb_ringbuffer *rbuf, size_t idx,
                int offset, u8* buf, size_t len)
{
    size_t todo;
    size_t split;
    size_t pktlen;

    pktlen = rbuf->data[idx] << 8;
    pktlen |= rbuf->data[(idx + 1) % rbuf->size];
    if (offset > pktlen) return -EINVAL;
    if ((offset + len) > pktlen) len = pktlen - offset;

    idx = (idx + DVB_RINGBUFFER_PKTHDRSIZE + offset) % rbuf->size;
    todo = len;
    split = ((idx + len) > rbuf->size) ? rbuf->size - idx : 0;
    if (split > 0) {
        memcpy(buf, rbuf->data+idx, split);
        buf += split;
        todo -= split;
        idx = 0;
    }
    memcpy(buf, rbuf->data+idx, todo);
    return len;
}

void dvb_ringbuffer_pkt_dispose(struct dvb_ringbuffer *rbuf, size_t idx)
{
    size_t pktlen;

    rbuf->data[(idx + 2) % rbuf->size] = PKT_DISPOSED;

    // clean up disposed packets
    while(dvb_ringbuffer_avail(rbuf) > DVB_RINGBUFFER_PKTHDRSIZE) {
        if (DVB_RINGBUFFER_PEEK(rbuf, 2) == PKT_DISPOSED) {
            pktlen = DVB_RINGBUFFER_PEEK(rbuf, 0) << 8;
            pktlen |= DVB_RINGBUFFER_PEEK(rbuf, 1);
            DVB_RINGBUFFER_SKIP(rbuf, pktlen + DVB_RINGBUFFER_PKTHDRSIZE);
        } else {
            // first packet is not disposed, so we stop cleaning now
            break;
        }
    }
}

ssize_t dvb_ringbuffer_pkt_next(struct dvb_ringbuffer *rbuf, size_t idx, size_t* pktlen)
{
    int consumed;
    int curpktlen;
    int curpktstatus;

    if (idx == -1) {
           idx = rbuf->pread;
    } else {
        curpktlen = rbuf->data[idx] << 8;
        curpktlen |= rbuf->data[(idx + 1) % rbuf->size];
        idx = (idx + curpktlen + DVB_RINGBUFFER_PKTHDRSIZE) % rbuf->size;
    }

    consumed = (idx - rbuf->pread) % rbuf->size;

    while((dvb_ringbuffer_avail(rbuf) - consumed) > DVB_RINGBUFFER_PKTHDRSIZE) {

        curpktlen = rbuf->data[idx] << 8;
        curpktlen |= rbuf->data[(idx + 1) % rbuf->size];
        curpktstatus = rbuf->data[(idx + 2) % rbuf->size];

        if (curpktstatus == PKT_READY) {
            *pktlen = curpktlen;
            return idx;
        }

        consumed += curpktlen + DVB_RINGBUFFER_PKTHDRSIZE;
        idx = (idx + curpktlen + DVB_RINGBUFFER_PKTHDRSIZE) % rbuf->size;
    }

    // no packets available
    return -1;
}



EXPORT_SYMBOL(dvb_ringbuffer_init);
EXPORT_SYMBOL(dvb_ringbuffer_empty);
EXPORT_SYMBOL(dvb_ringbuffer_free);
EXPORT_SYMBOL(dvb_ringbuffer_avail);
EXPORT_SYMBOL(dvb_ringbuffer_flush_spinlock_wakeup);
EXPORT_SYMBOL(dvb_ringbuffer_read_user);
EXPORT_SYMBOL(dvb_ringbuffer_read);
EXPORT_SYMBOL(dvb_ringbuffer_write);