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 
137 
138 /**
139  * Write a packet into the ringbuffer.
140  *
141  * <rbuf> Ringbuffer to write to.
142  * <buf> Buffer to write.
143  * <len> Length of buffer (currently limited to 65535 bytes max).
144  * returns Number of bytes written, or -EFAULT, -ENOMEM, -EVINAL.
145  */
146 extern ssize_t dvb_ringbuffer_pkt_write(struct dvb_ringbuffer *rbuf, u8* buf,
147 					size_t len);
148 
149 /**
150  * Read from a packet in the ringbuffer. Note: unlike dvb_ringbuffer_read(), this
151  * does NOT update the read pointer in the ringbuffer. You must use
152  * dvb_ringbuffer_pkt_dispose() to mark a packet as no longer required.
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  * <usermem> Set to 1 if <buf> is in userspace.
160  * returns Number of bytes read, or -EFAULT.
161  */
162 extern ssize_t dvb_ringbuffer_pkt_read_user(struct dvb_ringbuffer *rbuf, size_t idx,
163 				       int offset, u8 __user *buf, size_t len);
164 extern ssize_t dvb_ringbuffer_pkt_read(struct dvb_ringbuffer *rbuf, size_t idx,
165 				       int offset, u8 *buf, size_t len);
166 
167 /**
168  * Dispose of a packet in the ring buffer.
169  *
170  * <rbuf> Ring buffer concerned.
171  * <idx> Packet index as returned by dvb_ringbuffer_pkt_next().
172  */
173 extern void dvb_ringbuffer_pkt_dispose(struct dvb_ringbuffer *rbuf, size_t idx);
174 
175 /**
176  * Get the index of the next packet in a ringbuffer.
177  *
178  * <rbuf> Ringbuffer concerned.
179  * <idx> Previous packet index, or -1 to return the first packet index.
180  * <pktlen> On success, will be updated to contain the length of the packet in bytes.
181  * returns Packet index (if >=0), or -1 if no packets available.
182  */
183 extern ssize_t dvb_ringbuffer_pkt_next(struct dvb_ringbuffer *rbuf, size_t idx, size_t* pktlen);
184 
185 
186 #endif /* _DVB_RINGBUFFER_H_ */
187