drivers/media/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         int               error;
  39
  40         wait_queue_head_t queue;
  41         spinlock_t        lock;
  42 };
  43
  44 #define DVB_RINGBUFFER_PKTHDRSIZE 3
  45
  46
  47 /*
  48  * Notes:
  49  * ------
  50  * (1) For performance reasons read and write routines don't check buffer sizes
  51  *     and/or number of bytes free/available. This has to be done before these
  52  *     routines are called. For example:
  53  *
  54  *     *** write @buflen: bytes ***
  55  *     free = dvb_ringbuffer_free(rbuf);
  56  *     if (free >= buflen)
  57  *         count = dvb_ringbuffer_write(rbuf, buffer, buflen);
  58  *     else
  59  *         ...
  60  *
  61  *     *** read min. 1000, max. @bufsize: bytes ***
  62  *     avail = dvb_ringbuffer_avail(rbuf);
  63  *     if (avail >= 1000)
  64  *         count = dvb_ringbuffer_read(rbuf, buffer, min(avail, bufsize));
  65  *     else
  66  *         ...
  67  *
  68  * (2) If there is exactly one reader and one writer, there is no need
  69  *     to lock read or write operations.
  70  *     Two or more readers must be locked against each other.
  71  *     Flushing the buffer counts as a read operation.
  72  *     Resetting the buffer counts as a read and write operation.
  73  *     Two or more writers must be locked against each other.
  74  */
  75
  76 /* initialize ring buffer, lock and queue */
  77 extern void dvb_ringbuffer_init(struct dvb_ringbuffer *rbuf, void *data, size_t len);
  78
  79 /* test whether buffer is empty */
  80 extern int dvb_ringbuffer_empty(struct dvb_ringbuffer *rbuf);
  81
  82 /* return the number of free bytes in the buffer */
  83 extern ssize_t dvb_ringbuffer_free(struct dvb_ringbuffer *rbuf);
  84
  85 /* return the number of bytes waiting in the buffer */
  86 extern ssize_t dvb_ringbuffer_avail(struct dvb_ringbuffer *rbuf);
  87
  88
  89 /*
  90  * Reset the read and write pointers to zero and flush the buffer
  91  * This counts as a read and write operation
  92  */
  93 extern void dvb_ringbuffer_reset(struct dvb_ringbuffer *rbuf);
  94
  95
  96 /* read routines & macros */
  97 /* ---------------------- */
  98 /* flush buffer */
  99 extern void dvb_ringbuffer_flush(struct dvb_ringbuffer *rbuf);
 100
 101 /* flush buffer protected by spinlock and wake-up waiting task(s) */
 102 extern void dvb_ringbuffer_flush_spinlock_wakeup(struct dvb_ringbuffer *rbuf);
 103
 104 /* peek at byte @offs: in the buffer */
 105 #define DVB_RINGBUFFER_PEEK(rbuf,offs)  \
 106                         (rbuf)->data[((rbuf)->pread+(offs))%(rbuf)->size]
 107
 108 /* advance read ptr by @num: bytes */
 109 #define DVB_RINGBUFFER_SKIP(rbuf,num)   \
 110                         (rbuf)->pread=((rbuf)->pread+(num))%(rbuf)->size
 111
 112 /*
 113  * read @len: bytes from ring buffer into @buf:
 114  * @usermem: specifies whether @buf: resides in user space
 115  * returns number of bytes transferred or -EFAULT
 116  */
 117 extern ssize_t dvb_ringbuffer_read_user(struct dvb_ringbuffer *rbuf,
 118                                    u8 __user *buf, size_t len);
 119 extern void dvb_ringbuffer_read(struct dvb_ringbuffer *rbuf,
 120                                    u8 *buf, size_t len);
 121
 122
 123 /* write routines & macros */
 124 /* ----------------------- */
 125 /* write single byte to ring buffer */
 126 #define DVB_RINGBUFFER_WRITE_BYTE(rbuf,byte)    \
 127                         { (rbuf)->data[(rbuf)->pwrite]=(byte); \
 128                         (rbuf)->pwrite=((rbuf)->pwrite+1)%(rbuf)->size; }
 129 /*
 130  * write @len: bytes to ring buffer
 131  * @usermem: specifies whether @buf: resides in user space
 132  * returns number of bytes transferred or -EFAULT
 133 */
 134 extern ssize_t dvb_ringbuffer_write(struct dvb_ringbuffer *rbuf, const u8 *buf,
 135                                     size_t len);
 136 extern ssize_t dvb_ringbuffer_write_user(struct dvb_ringbuffer *rbuf,
 137                                          const u8 __user *buf, size_t len);
 138
 139
 140 /**
 141  * dvb_ringbuffer_pkt_write - Write a packet into the ringbuffer.
 142  *
 143  * @rbuf: Ringbuffer to write to.
 144  * @buf: Buffer to write.
 145  * @len: Length of buffer (currently limited to 65535 bytes max).
 146  * returns Number of bytes written, or -EFAULT, -ENOMEM, -EVINAL.
 147  */
 148 extern ssize_t dvb_ringbuffer_pkt_write(struct dvb_ringbuffer *rbuf, u8* buf,
 149                                         size_t len);
 150
 151 /**
 152  * dvb_ringbuffer_pkt_read_user - Read from a packet in the ringbuffer.
 153  *
 154  * @rbuf: Ringbuffer concerned.
 155  * @idx: Packet index as returned by dvb_ringbuffer_pkt_next().
 156  * @offset: Offset into packet to read from.
 157  * @buf: Destination buffer for data.
 158  * @len: Size of destination buffer.
 159  *
 160  * returns Number of bytes read, or -EFAULT.
 161  *
 162  * .. note::
 163  *
 164  *    unlike dvb_ringbuffer_read(), this does **NOT** update the read pointer
 165  *    in the ringbuffer. You must use dvb_ringbuffer_pkt_dispose() to mark a
 166  *    packet as no longer required.
 167  */
 168 extern ssize_t dvb_ringbuffer_pkt_read_user(struct dvb_ringbuffer *rbuf,
 169                                             size_t idx,
 170                                             int offset, u8 __user *buf,
 171                                             size_t len);
 172
 173 /**
 174  * dvb_ringbuffer_pkt_read - Read from a packet in the ringbuffer.
 175  * Note: unlike dvb_ringbuffer_read_user(), this DOES update the read pointer
 176  * in the ringbuffer.
 177  *
 178  * @rbuf: Ringbuffer concerned.
 179  * @idx: Packet index as returned by dvb_ringbuffer_pkt_next().
 180  * @offset: Offset into packet to read from.
 181  * @buf: Destination buffer for data.
 182  * @len: Size of destination buffer.
 183  *
 184  * returns Number of bytes read, or -EFAULT.
 185  */
 186 extern ssize_t dvb_ringbuffer_pkt_read(struct dvb_ringbuffer *rbuf, size_t idx,
 187                                        int offset, u8 *buf, size_t len);
 188
 189 /**
 190  * dvb_ringbuffer_pkt_dispose - Dispose of a packet in the ring buffer.
 191  *
 192  * @rbuf: Ring buffer concerned.
 193  * @idx: Packet index as returned by dvb_ringbuffer_pkt_next().
 194  */
 195 extern void dvb_ringbuffer_pkt_dispose(struct dvb_ringbuffer *rbuf, size_t idx);
 196
 197 /**
 198  * dvb_ringbuffer_pkt_next - Get the index of the next packet in a ringbuffer.
 199  *
 200  * @rbuf: Ringbuffer concerned.
 201  * @idx: Previous packet index, or -1 to return the first packet index.
 202  * @pktlen: On success, will be updated to contain the length of the packet in bytes.
 203  * returns Packet index (if >=0), or -1 if no packets available.
 204  */
 205 extern ssize_t dvb_ringbuffer_pkt_next(struct dvb_ringbuffer *rbuf, size_t idx, size_t* pktlen);
 206
 207
 208 #endif /* _DVB_RINGBUFFER_H_ */