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33 .Nd SCSI CD-ROM driver
36 .Cd "options ""CHANGER_MIN_BUSY_SECONDS=3"""
37 .Cd "options ""CHANGER_MAX_BUSY_SECONDS=11""
41 driver provides support for a
44 (Compact Disc-Read Only Memory) drive.
45 In an attempt to look like a regular disk, the
47 driver synthesizes a partition table, with one partition covering the entire
49 It is possible to modify this partition table using
51 but it will only last until the
54 In general the interfaces are similar to those described by
61 adapter is probed during boot, the
63 bus is scanned for devices.
64 Any devices found which answer as CDROM
65 (type 5) or WORM (type 4) type devices will be `attached' to the
70 the first device found will be attached as
77 it is possible to specify what cd unit a device should
78 come on line as; refer to
80 for details on kernel configuration.
84 may be used to read the synthesized
86 structure, which will contain correct figures for the size of the
88 should that information be required.
89 .Sh KERNEL CONFIGURATION
92 devices may be attached to the system regardless of system
93 configuration as all resources are dynamically allocated.
104 .In sys/disklabel.h .
106 .Bl -tag -width CDIOCREADSUBCHANNEL
109 .Pq Li "struct disklabel"
110 Read or write the in-core copy of the disklabel for the
112 The disklabel is initialized with information
113 read from the scsi inquiry commands, and should be the same as
114 the information printed at boot.
115 This structure is defined in
117 .It Dv CDIOCCAPABILITY
118 .Pq Li "struct ioc_capability"
119 Retrieve information from the drive on what features it supports.
120 The information is returned in the following structure:
121 .Bd -literal -offset indent
122 struct ioc_capability {
123 u_long play_function;
124 #define CDDOPLAYTRK 0x00000001
125 /* Can play tracks/index */
126 #define CDDOPLAYMSF 0x00000002
127 /* Can play msf to msf */
128 #define CDDOPLAYBLOCKS 0x00000004
129 /* Can play range of blocks */
130 #define CDDOPAUSE 0x00000100
131 /* Output can be paused */
132 #define CDDORESUME 0x00000200
133 /* Output can be resumed */
134 #define CDDORESET 0x00000400
135 /* Drive can be completely reset */
136 #define CDDOSTART 0x00000800
137 /* Audio can be started */
138 #define CDDOSTOP 0x00001000
139 /* Audio can be stopped */
140 #define CDDOPITCH 0x00002000
141 /* Audio pitch can be changed */
143 u_long routing_function;
144 #define CDREADVOLUME 0x00000001
145 /* Volume settings can be read */
146 #define CDSETVOLUME 0x00000002
147 /* Volume settings can be set */
148 #define CDSETMONO 0x00000100
149 /* Output can be set to mono */
150 #define CDSETSTEREO 0x00000200
151 /* Output can be set to stereo (def) */
152 #define CDSETLEFT 0x00000400
153 /* Output can be set to left only */
154 #define CDSETRIGHT 0x00000800
155 /* Output can be set to right only */
156 #define CDSETMUTE 0x00001000
157 /* Output can be muted */
158 #define CDSETPATCH 0x00008000
159 /* Direct routing control allowed */
161 u_long special_function;
162 #define CDDOEJECT 0x00000001
163 /* The tray can be opened */
164 #define CDDOCLOSE 0x00000002
165 /* The tray can be closed */
166 #define CDDOLOCK 0x00000004
167 /* The tray can be locked */
168 #define CDREADHEADER 0x00000100
169 /* Can read Table of Contents */
170 #define CDREADENTRIES 0x00000200
171 /* Can read TOC Entries */
172 #define CDREADSUBQ 0x00000200
173 /* Can read Subchannel info */
174 #define CDREADRW 0x00000400
175 /* Can read subcodes R-W */
176 #define CDHASDEBUG 0x00004000
177 /* The tray has dynamic debugging */
180 .It Dv CDIOCPLAYTRACKS
181 .Pq Li "struct ioc_play_track"
182 Start audio playback given a track address and length.
183 The structure is defined as follows:
184 .Bd -literal -offset indent
185 struct ioc_play_track
193 .It Dv CDIOCPLAYBLOCKS
194 .Pq Li "struct ioc_play_blocks"
195 Start audio playback given a block address and length.
196 The structure is defined as follows:
197 .Bd -literal -offset indent
198 struct ioc_play_blocks
205 .Pq Li "struct ioc_play_msf"
206 Start audio playback given a `minutes-seconds-frames' address and
208 The structure is defined as follows:
209 .Bd -literal -offset indent
220 .It Dv CDIOCREADSUBCHANNEL
221 .Pq Li "struct ioc_read_subchannel"
222 Read information from the subchannel at the location specified by this
224 .Bd -literal -offset indent
225 struct ioc_read_subchannel {
226 u_char address_format;
227 #define CD_LBA_FORMAT 1
228 #define CD_MSF_FORMAT 2
230 #define CD_SUBQ_DATA 0
231 #define CD_CURRENT_POSITION 1
232 #define CD_MEDIA_CATALOG 2
233 #define CD_TRACK_INFO 3
236 struct cd_sub_channel_info *data;
239 .It Dv CDIOREADTOCHEADER
240 .Pq Li "struct ioc_toc_header"
241 Return summary information about the table of contents for the mounted
243 The information is returned into the following structure:
244 .Bd -literal -offset indent
245 struct ioc_toc_header {
247 u_char starting_track;
251 .It Dv CDIOREADTOCENTRYS
252 .Pq Li "struct ioc_read_toc_entry"
253 Return information from the table of contents entries mentioned.
254 .Pq Yes, this command name is misspelled.
255 The argument structure is defined as follows:
256 .Bd -literal -offset indent
257 struct ioc_read_toc_entry {
258 u_char address_format;
259 u_char starting_track;
261 struct cd_toc_entry *data;
264 The requested data is written into an area of size
269 .Pq Li "struct ioc_patch"
270 Attach various audio channels to various output channels.
271 The argument structure is defined thusly:
272 .Bd -literal -offset indent
275 /* one for each channel */
280 .Pq Li "struct ioc_vol"
281 Get (set) information about the volume settings of the output channels.
282 The argument structure is as follows:
283 .Bd -literal -offset indent
287 /* one for each channel */
291 Patch all output channels to all source channels.
292 .It Dv CDIOCSETSTEREO
293 Patch left source channel to the left output channel and the right
294 source channel to the right output channel.
296 Mute output without changing the volume settings.
299 Attach both output channels to the left (right) source channel.
302 Turn on (off) debugging for the appropriate device.
305 Pause (resume) audio play, without resetting the location of the read-head.
310 Tell the drive to spin-up (-down) the
314 Tell the drive to allow (prevent) manual ejection of the
317 Not all drives support this feature.
322 Tell the drive to close its door and load the media.
323 Not all drives support this feature.
325 .Pq Li "struct ioc_pitch"
326 For drives that support it, this command instructs the drive to play
327 the audio at a faster or slower rate than normal.
330 between -32767 and -1 result in slower playback; a zero value
331 indicates normal speed; and values from 1 to 32767 give faster
333 Drives with less than 16 bits of resolution will silently
334 ignore less-significant bits.
335 The structure is defined thusly:
336 .Bd -literal -offset indent
346 is changed in a drive controlled by the
348 driver, then the act of changing the media will invalidate the
349 disklabel and information held within the kernel.
351 all accesses to the device will be discarded until there are no more
352 open file descriptors referencing the device.
353 During this period, all
354 new open attempts will be rejected.
355 When no more open file descriptors
356 reference the device, the first next open will load a new set of
357 parameters (including disklabel) for the drive.
359 The audio code in the
363 standard audio commands.
366 manufacturers have not followed the standard, there are many
368 drives for which audio will not work.
369 Some work is planned to support
370 some of the more common `broken'
372 drives; however, this is not yet under way.
373 .Sh CHANGER OPERATION
374 This driver has built-in support for LUN-based CD changers.
376 changer is a drive that can hold two or more CDs, but only has one CD
378 Each CD in the drive shows up as a separate logical unit
384 driver automatically recognizes LUN-based changers, and routes commands for
385 changers through an internal scheduler.
386 The scheduler prevents changer
387 "thrashing", which is caused by sending commands to different LUNs in the
388 changer at the same time.
390 The scheduler honors minimum and maximum time
391 quanta that the driver will spend on a particular LUN.
393 is the guaranteed minimum amount of time that the driver will spend on a
394 given LUN, even if there is no outstanding I/O for that LUN.
396 time is the maximum amount of time the changer will spend on a LUN if there
397 is outstanding I/O for another LUN.
398 If there is no outstanding I/O for
399 another LUN, the driver will allow indefinite access to a given LUN.
401 The minimum and maximum time quanta are configurable via kernel options and
402 also via sysctl and kernel tunable variables.
403 The kernel options are:
407 .Cd "options ""CHANGER_MIN_BUSY_SECONDS=3"""
409 .Cd "options ""CHANGER_MAX_BUSY_SECONDS=11"""
412 The sysctl/kernel tunable variables are:
416 .Va kern.cam.cd.changer.min_busy_seconds
418 .Va kern.cam.cd.changer.max_busy_seconds
421 It is suggested that the user try experimenting with the minimum and
422 maximum timeouts via the sysctl variables to arrive at the proper values
424 Once you have settled on the proper timeouts for your
425 changer, you can then put them in your kernel config file.
427 If your system does have a LUN-based changer, you may notice that the
428 probe messages for the various LUNs of the changer will continue to appear
429 while the boot process is going on.
430 This is normal, and is caused by the
431 changer scheduling code.
433 The following variables are available as both
439 .It kern.cam.cd.retry_count
441 This variable determines how many times the
443 driver will retry a READ or WRITE command.
444 This does not affect the number of retries used during probe time or for
448 This value currently defaults to 4.
449 .It kern.cam.cd.%d.minimum_cmd_size
453 driver attempts to automatically determine whether the drive it is talking
454 to supports 6 byte or 10 byte MODE SENSE/MODE SELECT operations.
457 drives only support 6 byte commands, and
459 drives only support 10 byte commands.
462 driver first attempts to determine whether the protocol in use typically
463 supports 6 byte commands by issuing a CAM Path Inquiry CCB.
464 It will then default to 6 byte or 10 byte commands as appropriate.
467 driver defaults to using 6 byte commands (assuming the protocol the drive
468 speaks claims to support 6 byte commands), until one fails with a
470 ILLEGAL REQUEST error.
471 Then it tries the 10 byte version of the command to
472 see if that works instead.
473 Users can change the default via per-drive
474 sysctl variables and loader tunables.
477 is the unit number of the drive in question.
478 Valid minimum command sizes
480 Any value above 6 will be rounded to 10, and any value below
481 6 will be rounded to 6.
482 .It kern.cam.cd.changer.min_busy_seconds
483 .It kern.cam.cd.changer.max_busy_seconds
485 Tune how long individual LUNs are 'locked' for I/O operations to
486 optimize changer operation.
487 See CHANGER OPERATION section for information on how to use these items.
490 .Bl -tag -width /dev/cd[0-9][a-h] -compact
491 .It Pa /dev/cd[0-9][a-h]
507 driver is based upon the
509 driver written by Julian Elischer, which appeared in
514 driver was written by Kenneth Merry and first appeared in
517 The names of the structures used for the third argument to
519 were poorly chosen, and a number of spelling errors have survived in
524 There is no mechanism currently to set different minimum and maximum
525 timeouts for different CD changers; the timeout values set by the kernel
526 options or the sysctl variables apply to all LUN-based CD changers in the
528 It is possible to implement such support, but the sysctl
529 implementation at least would be rather inelegant, because of the current
530 inability of the sysctl code to handle the addition of nodes after compile
532 Thus, it would take one dynamically sized sysctl variable and a
533 userland utility to get/set the timeout values.
534 Implementation of separate
535 timeouts for different CD devices in the kernel config file would likely
536 require modification of
538 to support the two timeouts when hardwiring