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1 .\" Copyright (c) 1996
2 .\" Julian Elischer <julian@FreeBSD.org>. All rights reserved.
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4 .\" Redistribution and use in source and binary forms, with or without
5 .\" modification, are permitted provided that the following conditions
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14 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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16 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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19 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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26 .\" $FreeBSD: src/share/man/man4/cd.4,v 1.17.2.8 2003/06/03 14:32:09 hmp Exp $
27 .\"
28 .Dd February 18, 2019
29 .Dt CD 4
30 .Os
31 .Sh NAME
32 .Nm cd
33 .Nd SCSI CD-ROM driver
34 .Sh SYNOPSIS
35 .Cd device cd
36 .Cd device cd1 at scbus0 target 4 unit 0
37 .Cd "options CHANGER_MIN_BUSY_SECONDS=3"
38 .Cd "options CHANGER_MAX_BUSY_SECONDS=11"
39 .Sh DESCRIPTION
40 The
41 .Nm
42 driver provides support for a
43 .Tn SCSI
44 .Tn CD-ROM
45 (Compact Disc-Read Only Memory) drive.
46 In an attempt to look like a regular disk, the
47 .Nm
48 driver synthesizes a partition table, with one partition covering the entire
49 .Tn CD-ROM .
50 It is possible to modify this partition table using
51 .Xr disklabel 8 ,
52 but it will only last until the
53 .Tn CD-ROM
54 is unmounted.
55 In general the interfaces are similar to those described by
56 .Xr ad 4
57 and
58 .Xr da 4 .
59 .Pp
60 As the
61 .Tn SCSI
62 adapter is probed during boot, the
63 .Tn SCSI
64 bus is scanned for devices.
65 Any devices found which answer as CDROM
66 (type 5) or WORM (type 4) type devices will be `attached' to the
67 .Nm
68 driver.
69 Prior to
70 .Fx 2.1 ,
71 the first device found will be attached as
72 .Li cd0
73 the next,
74 .Li cd1 ,
75 etc.
76 Beginning in
77 .Fx 2.1
78 it is possible to specify what cd unit a device should
79 come on line as; refer to
80 .Xr scsi 4
81 for details on kernel configuration.
82 .Pp
83 The
84 .Cd target
85 string is followed by the device's standard
86 .Tn SCSI
87 device ID number.
88 The
89 .Cd unit
90 string is followed by the Logical Unit Number
91 .Pq Tn LUN
92 of the
93 .Tn SCSI
94 device's sub-device, if any, or zero.
95 .Pp
96 The system utility
97 .Xr disklabel 8
98 may be used to read the synthesized
99 disk label
100 structure, which will contain correct figures for the size of the
101 .Tn CD-ROM
102 should that information be required.
103 .Sh KERNEL CONFIGURATION
104 Any number of
105 .Tn CD-ROM
106 devices may be attached to the system regardless of system
107 configuration as all resources are dynamically allocated.
108 .Sh IOCTLS
109 The following
110 .Xr ioctl 2
111 calls which apply to
112 .Tn SCSI
113 .Tn CD-ROM
114 drives are defined
115 in the header files
116 .In sys/cdio.h
117 and
118 .In sys/disklabel.h .
119 .Bl -tag -width ".Dv CDIOCREADSUBCHANNEL"
120 .It Dv DIOCGDINFO
121 .It Dv DIOCSDINFO
122 .Pq Li "struct disklabel"
123 Read or write the in-core copy of the disklabel for the
124 drive.
125 The disklabel is initialized with information
126 read from the scsi inquiry commands, and should be the same as
127 the information printed at boot.
128 This structure is defined in
129 .Xr disklabel 5 .
130 .It Dv CDIOCPLAYTRACKS
131 .Pq Li "struct ioc_play_track"
132 Start audio playback given a track address and length.
133 The structure is defined as follows:
134 .Bd -literal -offset indent
135 struct ioc_play_track
136 {
137 u_char start_track;
138 u_char start_index;
139 u_char end_track;
140 u_char end_index;
141 };
142 .Ed
143 .It Dv CDIOCPLAYBLOCKS
144 .Pq Li "struct ioc_play_blocks"
145 Start audio playback given a block address and length.
146 The structure is defined as follows:
147 .Bd -literal -offset indent
148 struct ioc_play_blocks
149 {
150 int blk;
151 int len;
152 };
153 .Ed
154 .It Dv CDIOCPLAYMSF
155 .Pq Li "struct ioc_play_msf"
156 Start audio playback given a `minutes-seconds-frames' address and
157 length.
158 The structure is defined as follows:
159 .Bd -literal -offset indent
160 struct ioc_play_msf
161 {
162 u_char start_m;
163 u_char start_s;
164 u_char start_f;
165 u_char end_m;
166 u_char end_s;
167 u_char end_f;
168 };
169 .Ed
170 .It Dv CDIOCREADSUBCHANNEL
171 .Pq Li "struct ioc_read_subchannel"
172 Read information from the subchannel at the location specified by this
173 structure:
174 .Bd -literal -offset indent
175 struct ioc_read_subchannel {
176 u_char address_format;
177 #define CD_LBA_FORMAT 1
178 #define CD_MSF_FORMAT 2
179 u_char data_format;
180 #define CD_SUBQ_DATA 0
181 #define CD_CURRENT_POSITION 1
182 #define CD_MEDIA_CATALOG 2
183 #define CD_TRACK_INFO 3
184 u_char track;
185 int data_len;
186 struct cd_sub_channel_info *data;
187 };
188 .Ed
189 .It Dv CDIOREADTOCHEADER
190 .Pq Li "struct ioc_toc_header"
191 Return summary information about the table of contents for the mounted
192 .Tn CD-ROM .
193 The information is returned into the following structure:
194 .Bd -literal -offset indent
195 struct ioc_toc_header {
196 u_short len;
197 u_char starting_track;
198 u_char ending_track;
199 };
200 .Ed
201 .It Dv CDIOREADTOCENTRYS
202 .Pq Li "struct ioc_read_toc_entry"
203 Return information from the table of contents entries mentioned.
204 .Pq Yes, this command name is misspelled.
205 The argument structure is defined as follows:
206 .Bd -literal -offset indent
207 struct ioc_read_toc_entry {
208 u_char address_format;
209 u_char starting_track;
210 u_short data_len;
211 struct cd_toc_entry *data;
212 };
213 .Ed
214 The requested data is written into an area of size
215 .Li data_len
216 and pointed to by
217 .Li data .
218 .It Dv CDIOCSETPATCH
219 .Pq Li "struct ioc_patch"
220 Attach various audio channels to various output channels.
221 The argument structure is defined thusly:
222 .Bd -literal -offset indent
223 struct ioc_patch {
224 u_char patch[4];
225 /* one for each channel */
226 };
227 .Ed
228 .It Dv CDIOCGETVOL
229 .It Dv CDIOCSETVOL
230 .Pq Li "struct ioc_vol"
231 Get (set) information about the volume settings of the output channels.
232 The argument structure is as follows:
233 .Bd -literal -offset indent
234 struct ioc_vol
235 {
236 u_char vol[4];
237 /* one for each channel */
238 };
239 .Ed
240 .It Dv CDIOCSETMONO
241 Patch all output channels to all source channels.
242 .It Dv CDIOCSETSTEREO
243 Patch left source channel to the left output channel and the right
244 source channel to the right output channel.
245 .It Dv CDIOCSETMUTE
246 Mute output without changing the volume settings.
247 .It Dv CDIOCSETLEFT
248 .It Dv CDIOCSETRIGHT
249 Attach both output channels to the left (right) source channel.
250 .It Dv CDIOCSETDEBUG
251 .It Dv CDIOCCLRDEBUG
252 Turn on (off) debugging for the appropriate device.
253 .It Dv CDIOCPAUSE
254 .It Dv CDIOCRESUME
255 Pause (resume) audio play, without resetting the location of the read-head.
256 .It Dv CDIOCRESET
257 Reset the drive.
258 .It Dv CDIOCSTART
259 .It Dv CDIOCSTOP
260 Tell the drive to spin-up (-down) the
261 .Tn CD-ROM .
262 .It Dv CDIOCALLOW
263 .It Dv CDIOCPREVENT
264 Tell the drive to allow (prevent) manual ejection of the
265 .Tn CD-ROM
266 disc. Not all drives support this feature.
267 .It Dv CDIOCEJECT
268 Eject the
269 .Tn CD-ROM .
270 .It Dv CDIOCCLOSE
271 Tell the drive to close its door and load the media.
272 Not all drives support this feature.
273 .El
274 .Sh NOTES
275 When a
276 .Tn CD-ROM
277 is changed in a drive controlled by the
278 .Nm
279 driver, then the act of changing the media will invalidate the
280 disklabel and information held within the kernel.
281 To stop corruption,
282 all accesses to the device will be discarded until there are no more
283 open file descriptors referencing the device.
284 During this period, all
285 new open attempts will be rejected.
286 When no more open file descriptors
287 reference the device, the first next open will load a new set of
288 parameters (including disklabel) for the drive.
289 .Pp
290 The audio code in the
291 .Nm
292 driver only support
293 .Tn SCSI-2
294 standard audio commands.
295 Because many
296 .Tn CD-ROM
297 manufacturers have not followed the standard, there are many
298 .Tn CD-ROM
299 drives for which audio will not work.
300 Some work is planned to support
301 some of the more common `broken'
302 .Tn CD-ROM
303 drives; however, this is not yet under way.
304 .Sh CHANGER OPERATION
305 This driver has built-in support for LUN-based CD changers.
306 A LUN-based CD
307 changer is a drive that can hold two or more CDs, but only has one CD
308 player mechanism.
309 Each CD in the drive shows up as a separate logical unit
310 on the
311 .Tn SCSI
312 bus. The
313 .Nm
314 driver automatically recognizes LUN-based changers, and routes commands for
315 changers through an internal scheduler.
316 The scheduler prevents changer
317 "thrashing", which is caused by sending commands to different LUNs in the
318 changer at the same time.
319 .Pp
320 The scheduler honors minimum and maximum time
321 quanta that the driver will spend on a particular LUN.
322 The minimum time
323 is the guaranteed minimum amount of time that the driver will spend on a
324 given LUN, even if there is no outstanding I/O for that LUN.
325 The maximum
326 time is the maximum amount of time the changer will spend on a LUN if there
327 is outstanding I/O for another LUN.
328 If there is no outstanding I/O for
329 another LUN, the driver will allow indefinite access to a given LUN.
330 .Pp
331 The minimum and maximum time quanta are configurable via kernel options and
332 also via sysctl variables.
333 The kernel options are:
334 .Pp
335 .Bl -item -compact
336 .It
337 .Cd "options ""CHANGER_MIN_BUSY_SECONDS=3"""
338 .It
339 .Cd "options ""CHANGER_MAX_BUSY_SECONDS=11"""
340 .El
341 .Pp
342 The sysctl variables are:
343 .Pp
344 .Bl -item -compact
345 .It
346 .Va kern.cam.cd.changer.min_busy_seconds
347 .It
348 .Va kern.cam.cd.changer.max_busy_seconds
349 .El
350 .Pp
351 It is suggested that the user try experimenting with the minimum and
352 maximum timeouts via the sysctl variables to arrive at the proper values
353 for your changer.
354 Once you have settled on the proper timeouts for your
355 changer, you can then put them in your kernel config file.
356 .Pp
357 If your system does have a LUN-based changer, you may notice that the
358 probe messages for the various LUNs of the changer will continue to appear
359 while the boot process is going on.
360 This is normal, and is caused by the
361 changer scheduling code.
362 .Sh FILES
363 .Bl -tag -width /dev/cd[0-9][a-h] -compact
364 .It Pa /dev/cd[0-9][a-h]
365 raw mode
366 .Tn CD-ROM
367 devices
368 .El
369 .Sh DIAGNOSTICS
370 None.
371 .Sh SEE ALSO
372 .Xr da 4 ,
373 .Xr scsi 4 ,
374 .Xr disklabel 5 ,
375 .Xr disklabel 8 ,
376 .Xr cd 9
377 .Sh HISTORY
378 This
379 .Nm
380 driver is based upon the
381 .Nm
382 driver written by Julian Elischer, which appeared in
383 .Bx 386 0.1 .
384 The
385 CAM version of the
386 .Nm
387 driver was written by Kenneth Merry and first appeared in
388 .Fx 3.0 .
389 .Sh BUGS
390 The names of the structures used for the third argument to
391 .Fn ioctl
392 were poorly chosen, and a number of spelling errors have survived in
393 the names of the
394 .Fn ioctl
395 commands.
396 .Pp
397 There is no mechanism currently to set different minimum and maximum
398 timeouts for different CD changers; the timeout values set by the kernel
399 options or the sysctl variables apply to all LUN-based CD changers in the
400 system.
401 It is possible to implement such support, but the sysctl
402 implementation at least would be rather inelegant, because of the current
403 inability of the sysctl code to handle the addition of nodes after compile
404 time.
405 Thus, it would take one dynamically sized sysctl variable and a
406 userland utility to get/set the timeout values.
407 Implementation of separate
408 timeouts for different CD devices in the kernel config file would likely
409 require modification of
410 .Xr config 8
411 to support the two timeouts when hardwiring
412 .Nm
413 devices.