ia64/linux-2.6.18-xen.hg

view drivers/ieee1394/dv1394.h @ 893:f994bfe9b93b

linux/blktap2: reduce TLB flush scope

c/s 885 added very coarse TLB flushing. Since these flushes always
follow single page updates, single page flushes (when available) are
sufficient.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
author Keir Fraser <keir.fraser@citrix.com>
date Thu Jun 04 10:32:57 2009 +0100 (2009-06-04)
parents 831230e53067
children
line source
1 /*
2 * dv1394.h - DV input/output over IEEE 1394 on OHCI chips
3 * Copyright (C)2001 Daniel Maas <dmaas@dcine.com>
4 * receive by Dan Dennedy <dan@dennedy.org>
5 *
6 * based on:
7 * video1394.h - driver for OHCI 1394 boards
8 * Copyright (C)1999,2000 Sebastien Rougeaux <sebastien.rougeaux@anu.edu.au>
9 * Peter Schlaile <udbz@rz.uni-karlsruhe.de>
10 *
11 * This program is free software; you can redistribute it and/or modify
12 * it under the terms of the GNU General Public License as published by
13 * the Free Software Foundation; either version 2 of the License, or
14 * (at your option) any later version.
15 *
16 * This program is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 * GNU General Public License for more details.
20 *
21 * You should have received a copy of the GNU General Public License
22 * along with this program; if not, write to the Free Software Foundation,
23 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
24 */
26 #ifndef _DV_1394_H
27 #define _DV_1394_H
29 /* This is the public user-space interface. Try not to break it. */
31 #define DV1394_API_VERSION 0x20011127
33 /* ********************
34 ** **
35 ** DV1394 API **
36 ** **
37 ********************
39 There are two methods of operating the DV1394 DV output device.
41 1)
43 The simplest is an interface based on write(): simply write
44 full DV frames of data to the device, and they will be transmitted
45 as quickly as possible. The FD may be set for non-blocking I/O,
46 in which case you can use select() or poll() to wait for output
47 buffer space.
49 To set the DV output parameters (e.g. whether you want NTSC or PAL
50 video), use the DV1394_INIT ioctl, passing in the parameters you
51 want in a struct dv1394_init.
53 Example 1:
54 To play a raw .DV file: cat foo.DV > /dev/dv1394
55 (cat will use write() internally)
57 Example 2:
58 static struct dv1394_init init = {
59 0x63, (broadcast channel)
60 4, (four-frame ringbuffer)
61 DV1394_NTSC, (send NTSC video)
62 0, 0 (default empty packet rate)
63 }
65 ioctl(fd, DV1394_INIT, &init);
67 while (1) {
68 read( <a raw DV file>, buf, DV1394_NTSC_FRAME_SIZE );
69 write( <the dv1394 FD>, buf, DV1394_NTSC_FRAME_SIZE );
70 }
72 2)
74 For more control over buffering, and to avoid unnecessary copies
75 of the DV data, you can use the more sophisticated the mmap() interface.
76 First, call the DV1394_INIT ioctl to specify your parameters,
77 including the number of frames in the ringbuffer. Then, calling mmap()
78 on the dv1394 device will give you direct access to the ringbuffer
79 from which the DV card reads your frame data.
81 The ringbuffer is simply one large, contiguous region of memory
82 containing two or more frames of packed DV data. Each frame of DV data
83 is 120000 bytes (NTSC) or 144000 bytes (PAL).
85 Fill one or more frames in the ringbuffer, then use the DV1394_SUBMIT_FRAMES
86 ioctl to begin I/O. You can use either the DV1394_WAIT_FRAMES ioctl
87 or select()/poll() to wait until the frames are transmitted. Next, you'll
88 need to call the DV1394_GET_STATUS ioctl to determine which ringbuffer
89 frames are clear (ready to be filled with new DV data). Finally, use
90 DV1394_SUBMIT_FRAMES again to send the new data to the DV output.
93 Example: here is what a four-frame ringbuffer might look like
94 during DV transmission:
97 frame 0 frame 1 frame 2 frame 3
99 *--------------------------------------*
100 | CLEAR | DV data | DV data | CLEAR |
101 *--------------------------------------*
102 <ACTIVE>
104 transmission goes in this direction --->>>
107 The DV hardware is currently transmitting the data in frame 1.
108 Once frame 1 is finished, it will automatically transmit frame 2.
109 (if frame 2 finishes before frame 3 is submitted, the device
110 will continue to transmit frame 2, and will increase the dropped_frames
111 counter each time it repeats the transmission).
114 If you called DV1394_GET_STATUS at this instant, you would
115 receive the following values:
117 n_frames = 4
118 active_frame = 1
119 first_clear_frame = 3
120 n_clear_frames = 2
122 At this point, you should write new DV data into frame 3 and optionally
123 frame 0. Then call DV1394_SUBMIT_FRAMES to inform the device that
124 it may transmit the new frames.
126 ERROR HANDLING
128 An error (buffer underflow/overflow or a break in the DV stream due
129 to a 1394 bus reset) can be detected by checking the dropped_frames
130 field of struct dv1394_status (obtained through the
131 DV1394_GET_STATUS ioctl).
133 The best way to recover from such an error is to re-initialize
134 dv1394, either by using the DV1394_INIT ioctl call, or closing the
135 file descriptor and opening it again. (note that you must unmap all
136 ringbuffer mappings when closing the file descriptor, or else
137 dv1394 will still be considered 'in use').
139 MAIN LOOP
141 For maximum efficiency and robustness against bus errors, you are
142 advised to model the main loop of your application after the
143 following pseudo-code example:
145 (checks of system call return values omitted for brevity; always
146 check return values in your code!)
148 while ( frames left ) {
150 struct pollfd *pfd = ...;
152 pfd->fd = dv1394_fd;
153 pfd->revents = 0;
154 pfd->events = POLLOUT | POLLIN; (OUT for transmit, IN for receive)
156 (add other sources of I/O here)
158 poll(pfd, 1, -1); (or select(); add a timeout if you want)
160 if (pfd->revents) {
161 struct dv1394_status status;
163 ioctl(dv1394_fd, DV1394_GET_STATUS, &status);
165 if (status.dropped_frames > 0) {
166 reset_dv1394();
167 } else {
168 for (int i = 0; i < status.n_clear_frames; i++) {
169 copy_DV_frame();
170 }
171 }
172 }
173 }
175 where copy_DV_frame() reads or writes on the dv1394 file descriptor
176 (read/write mode) or copies data to/from the mmap ringbuffer and
177 then calls ioctl(DV1394_SUBMIT_FRAMES) to notify dv1394 that new
178 frames are availble (mmap mode).
180 reset_dv1394() is called in the event of a buffer
181 underflow/overflow or a halt in the DV stream (e.g. due to a 1394
182 bus reset). To guarantee recovery from the error, this function
183 should close the dv1394 file descriptor (and munmap() all
184 ringbuffer mappings, if you are using them), then re-open the
185 dv1394 device (and re-map the ringbuffer).
187 */
190 /* maximum number of frames in the ringbuffer */
191 #define DV1394_MAX_FRAMES 32
193 /* number of *full* isochronous packets per DV frame */
194 #define DV1394_NTSC_PACKETS_PER_FRAME 250
195 #define DV1394_PAL_PACKETS_PER_FRAME 300
197 /* size of one frame's worth of DV data, in bytes */
198 #define DV1394_NTSC_FRAME_SIZE (480 * DV1394_NTSC_PACKETS_PER_FRAME)
199 #define DV1394_PAL_FRAME_SIZE (480 * DV1394_PAL_PACKETS_PER_FRAME)
202 /* ioctl() commands */
203 #include "ieee1394-ioctl.h"
206 enum pal_or_ntsc {
207 DV1394_NTSC = 0,
208 DV1394_PAL
209 };
214 /* this is the argument to DV1394_INIT */
215 struct dv1394_init {
216 /* DV1394_API_VERSION */
217 unsigned int api_version;
219 /* isochronous transmission channel to use */
220 unsigned int channel;
222 /* number of frames in the ringbuffer. Must be at least 2
223 and at most DV1394_MAX_FRAMES. */
224 unsigned int n_frames;
226 /* send/receive PAL or NTSC video format */
227 enum pal_or_ntsc format;
229 /* the following are used only for transmission */
231 /* set these to zero unless you want a
232 non-default empty packet rate (see below) */
233 unsigned long cip_n;
234 unsigned long cip_d;
236 /* set this to zero unless you want a
237 non-default SYT cycle offset (default = 3 cycles) */
238 unsigned int syt_offset;
239 };
241 /* NOTE: you may only allocate the DV frame ringbuffer once each time
242 you open the dv1394 device. DV1394_INIT will fail if you call it a
243 second time with different 'n_frames' or 'format' arguments (which
244 would imply a different size for the ringbuffer). If you need a
245 different buffer size, simply close and re-open the device, then
246 initialize it with your new settings. */
248 /* Q: What are cip_n and cip_d? */
250 /*
251 A: DV video streams do not utilize 100% of the potential bandwidth offered
252 by IEEE 1394 (FireWire). To achieve the correct rate of data transmission,
253 DV devices must periodically insert empty packets into the 1394 data stream.
254 Typically there is one empty packet per 14-16 data-carrying packets.
256 Some DV devices will accept a wide range of empty packet rates, while others
257 require a precise rate. If the dv1394 driver produces empty packets at
258 a rate that your device does not accept, you may see ugly patterns on the
259 DV output, or even no output at all.
261 The default empty packet insertion rate seems to work for many people; if
262 your DV output is stable, you can simply ignore this discussion. However,
263 we have exposed the empty packet rate as a parameter to support devices that
264 do not work with the default rate.
266 The decision to insert an empty packet is made with a numerator/denominator
267 algorithm. Empty packets are produced at an average rate of CIP_N / CIP_D.
268 You can alter the empty packet rate by passing non-zero values for cip_n
269 and cip_d to the INIT ioctl.
271 */
275 struct dv1394_status {
276 /* this embedded init struct returns the current dv1394
277 parameters in use */
278 struct dv1394_init init;
280 /* the ringbuffer frame that is currently being
281 displayed. (-1 if the device is not transmitting anything) */
282 int active_frame;
284 /* index of the first buffer (ahead of active_frame) that
285 is ready to be filled with data */
286 unsigned int first_clear_frame;
288 /* how many buffers, including first_clear_buffer, are
289 ready to be filled with data */
290 unsigned int n_clear_frames;
292 /* how many times the DV stream has underflowed, overflowed,
293 or otherwise encountered an error, since the previous call
294 to DV1394_GET_STATUS */
295 unsigned int dropped_frames;
297 /* N.B. The dropped_frames counter is only a lower bound on the actual
298 number of dropped frames, with the special case that if dropped_frames
299 is zero, then it is guaranteed that NO frames have been dropped
300 since the last call to DV1394_GET_STATUS.
301 */
302 };
305 #endif /* _DV_1394_H */