drivers/media/dvb/dvb-core/dvb_ringbuffer.h

   1 /*
   2  *
   3  * dvb_ringbuffer.h: ring buffer implementation for the dvb driver
   4  *
   5  * Copyright (C) 2003 Oliver Endriss
   6  * Copyright (C) 2004 Andrew de Quincey
   7  *
   8  * based on code originally found in av7110.c & dvb_ci.c:
   9  * Copyright (C) 1999-2003 Ralph Metzler & Marcus Metzler
  10  *                         for convergence integrated media GmbH
  11  *
  12  * This program is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU Lesser General Public License
  14  * as published by the Free Software Foundation; either version 2.1
  15  * of the License, or (at your option) any later version.
  16  *
  17  * This program is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU Lesser General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU Lesser General Public License
  23  * along with this program; if not, write to the Free Software
  24  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  25  */
  26
  27 #ifndef _DVB_RINGBUFFER_H_
  28 #define _DVB_RINGBUFFER_H_
  29
  30 #include <linux/spinlock.h>
  31 #include <linux/wait.h>
  32
  33 struct dvb_ringbuffer {
  34         u8               *data;
  35         ssize_t           size;
  36         ssize_t           pread;
  37         ssize_t           pwrite;
  38
  39         wait_queue_head_t queue;
  40         spinlock_t        lock;
  41 };
  42
  43 #define DVB_RINGBUFFER_PKTHDRSIZE 3
  44
  45
  46 /*
  47 ** Notes:
  48 ** ------
  49 ** (1) For performance reasons read and write routines don't check buffer sizes
  50 **     and/or number of bytes free/available. This has to be done before these
  51 **     routines are called. For example:
  52 **
  53 **     *** write <buflen> bytes ***
  54 **     free = dvb_ringbuffer_free(rbuf);
  55 **     if (free >= buflen)
  56 **         count = dvb_ringbuffer_write(rbuf, buffer, buflen);
  57 **     else
  58 **         ...
  59 **
  60 **     *** read min. 1000, max. <bufsize> bytes ***
  61 **     avail = dvb_ringbuffer_avail(rbuf);
  62 **     if (avail >= 1000)
  63 **         count = dvb_ringbuffer_read(rbuf, buffer, min(avail, bufsize), 0);
  64 **     else
  65 **         ...
  66 **
  67 ** (2) If there is exactly one reader and one writer, there is no need
  68 **     to lock read or write operations.
  69 **     Two or more readers must be locked against each other.
  70 **     Flushing the buffer counts as a read operation.
  71 **     Two or more writers must be locked against each other.
  72 */
  73
  74 /* initialize ring buffer, lock and queue */
  75 extern void dvb_ringbuffer_init(struct dvb_ringbuffer *rbuf, void *data, size_t len);
  76
  77 /* test whether buffer is empty */
  78 extern int dvb_ringbuffer_empty(struct dvb_ringbuffer *rbuf);
  79
  80 /* return the number of free bytes in the buffer */
  81 extern ssize_t dvb_ringbuffer_free(struct dvb_ringbuffer *rbuf);
  82
  83 /* return the number of bytes waiting in the buffer */
  84 extern ssize_t dvb_ringbuffer_avail(struct dvb_ringbuffer *rbuf);
  85
  86
  87 /* read routines & macros */
  88 /* ---------------------- */
  89 /* flush buffer */
  90 extern void dvb_ringbuffer_flush(struct dvb_ringbuffer *rbuf);
  91
  92 /* flush buffer protected by spinlock and wake-up waiting task(s) */
  93 extern void dvb_ringbuffer_flush_spinlock_wakeup(struct dvb_ringbuffer *rbuf);
  94
  95 /* peek at byte <offs> in the buffer */
  96 #define DVB_RINGBUFFER_PEEK(rbuf,offs)  \
  97                         (rbuf)->data[((rbuf)->pread+(offs))%(rbuf)->size]
  98
  99 /* advance read ptr by <num> bytes */
 100 #define DVB_RINGBUFFER_SKIP(rbuf,num)   \
 101                         (rbuf)->pread=((rbuf)->pread+(num))%(rbuf)->size
 102
 103 /*
 104 ** read <len> bytes from ring buffer into <buf>
 105 ** <usermem> specifies whether <buf> resides in user space
 106 ** returns number of bytes transferred or -EFAULT
 107 */
 108 extern ssize_t dvb_ringbuffer_read(struct dvb_ringbuffer *rbuf, u8 *buf,
 109                                    size_t len, int usermem);
 110
 111
 112 /* write routines & macros */
 113 /* ----------------------- */
 114 /* write single byte to ring buffer */
 115 #define DVB_RINGBUFFER_WRITE_BYTE(rbuf,byte)    \
 116                         { (rbuf)->data[(rbuf)->pwrite]=(byte); \
 117                         (rbuf)->pwrite=((rbuf)->pwrite+1)%(rbuf)->size; }
 118 /*
 119 ** write <len> bytes to ring buffer
 120 ** <usermem> specifies whether <buf> resides in user space
 121 ** returns number of bytes transferred or -EFAULT
 122 */
 123 extern ssize_t dvb_ringbuffer_write(struct dvb_ringbuffer *rbuf, const u8 *buf,
 124                                     size_t len);
 125
 126
 127 /**
 128  * Write a packet into the ringbuffer.
 129  *
 130  * <rbuf> Ringbuffer to write to.
 131  * <buf> Buffer to write.
 132  * <len> Length of buffer (currently limited to 65535 bytes max).
 133  * returns Number of bytes written, or -EFAULT, -ENOMEM, -EVINAL.
 134  */
 135 extern ssize_t dvb_ringbuffer_pkt_write(struct dvb_ringbuffer *rbuf, u8* buf,
 136                                         size_t len);
 137
 138 /**
 139  * Read from a packet in the ringbuffer. Note: unlike dvb_ringbuffer_read(), this
 140  * does NOT update the read pointer in the ringbuffer. You must use
 141  * dvb_ringbuffer_pkt_dispose() to mark a packet as no longer required.
 142  *
 143  * <rbuf> Ringbuffer concerned.
 144  * <idx> Packet index as returned by dvb_ringbuffer_pkt_next().
 145  * <offset> Offset into packet to read from.
 146  * <buf> Destination buffer for data.
 147  * <len> Size of destination buffer.
 148  * <usermem> Set to 1 if <buf> is in userspace.
 149  * returns Number of bytes read, or -EFAULT.
 150  */
 151 extern ssize_t dvb_ringbuffer_pkt_read(struct dvb_ringbuffer *rbuf, size_t idx,
 152                                        int offset, u8* buf, size_t len, int usermem);
 153
 154 /**
 155  * Dispose of a packet in the ring buffer.
 156  *
 157  * <rbuf> Ring buffer concerned.
 158  * <idx> Packet index as returned by dvb_ringbuffer_pkt_next().
 159  */
 160 extern void dvb_ringbuffer_pkt_dispose(struct dvb_ringbuffer *rbuf, size_t idx);
 161
 162 /**
 163  * Get the index of the next packet in a ringbuffer.
 164  *
 165  * <rbuf> Ringbuffer concerned.
 166  * <idx> Previous packet index, or -1 to return the first packet index.
 167  * <pktlen> On success, will be updated to contain the length of the packet in bytes.
 168  * returns Packet index (if >=0), or -1 if no packets available.
 169  */
 170 extern ssize_t dvb_ringbuffer_pkt_next(struct dvb_ringbuffer *rbuf, size_t idx, size_t* pktlen);
 171
 172
 173 #endif /* _DVB_RINGBUFFER_H_ */