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2 | README for the SCSI media changer driver | |
3 | ======================================== | |
4 | ||
5 | This is a driver for SCSI Medium Changer devices, which are listed | |
6 | with "Type: Medium Changer" in /proc/scsi/scsi. | |
7 | ||
8 | This is for *real* Jukeboxes. It is *not* supported to work with | |
9 | common small CD-ROM changers, neither one-lun-per-slot SCSI changers | |
10 | nor IDE drives. | |
11 | ||
12 | Userland tools available from here: | |
13 | http://linux.bytesex.org/misc/changer.html | |
14 | ||
15 | ||
16 | General Information | |
17 | ------------------- | |
18 | ||
19 | First some words about how changers work: A changer has 2 (possibly | |
20 | more) SCSI ID's. One for the changer device which controls the robot, | |
21 | and one for the device which actually reads and writes the data. The | |
22 | later may be anything, a MOD, a CD-ROM, a tape or whatever. For the | |
23 | changer device this is a "don't care", he *only* shuffles around the | |
24 | media, nothing else. | |
25 | ||
26 | ||
27 | The SCSI changer model is complex, compared to - for example - IDE-CD | |
28 | changers. But it allows to handle nearly all possible cases. It knows | |
29 | 4 different types of changer elements: | |
30 | ||
31 | media transport - this one shuffles around the media, i.e. the | |
32 | transport arm. Also known as "picker". | |
33 | storage - a slot which can hold a media. | |
34 | import/export - the same as above, but is accessable from outside, | |
35 | i.e. there the operator (you !) can use this to | |
36 | fill in and remove media from the changer. | |
37 | Sometimes named "mailslot". | |
38 | data transfer - this is the device which reads/writes, i.e. the | |
39 | CD-ROM / Tape / whatever drive. | |
40 | ||
41 | None of these is limited to one: A huge Jukebox could have slots for | |
42 | 123 CD-ROM's, 5 CD-ROM readers (and therefore 6 SCSI ID's: the changer | |
43 | and each CD-ROM) and 2 transport arms. No problem to handle. | |
44 | ||
45 | ||
46 | How it is implemented | |
47 | --------------------- | |
48 | ||
49 | I implemented the driver as character device driver with a NetBSD-like | |
50 | ioctl interface. Just grabbed NetBSD's header file and one of the | |
51 | other linux SCSI device drivers as starting point. The interface | |
52 | should be source code compatible with NetBSD. So if there is any | |
53 | software (anybody knows ???) which supports a BSDish changer driver, | |
54 | it should work with this driver too. | |
55 | ||
56 | Over time a few more ioctls where added, volume tag support for example | |
57 | wasn't covered by the NetBSD ioctl API. | |
58 | ||
59 | ||
60 | Current State | |
61 | ------------- | |
62 | ||
63 | Support for more than one transport arm is not implemented yet (and | |
64 | nobody asked for it so far...). | |
65 | ||
66 | I test and use the driver myself with a 35 slot cdrom jukebox from | |
67 | Grundig. I got some reports telling it works ok with tape autoloaders | |
68 | (Exabyte, HP and DEC). Some People use this driver with amanda. It | |
69 | works fine with small (11 slots) and a huge (4 MOs, 88 slots) | |
70 | magneto-optical Jukebox. Probably with lots of other changers too, most | |
71 | (but not all :-) people mail me only if it does *not* work... | |
72 | ||
73 | I don't have any device lists, neither black-list nor white-list. Thus | |
74 | it is quite useless to ask me whenever a specific device is supported or | |
75 | not. In theory every changer device which supports the SCSI-2 media | |
76 | changer command set should work out-of-the-box with this driver. If it | |
77 | doesn't, it is a bug. Either within the driver or within the firmware | |
78 | of the changer device. | |
79 | ||
80 | ||
81 | Using it | |
82 | -------- | |
83 | ||
84 | This is a character device with major number is 86, so use | |
85 | "mknod /dev/sch0 c 86 0" to create the special file for the driver. | |
86 | ||
87 | If the module finds the changer, it prints some messages about the | |
88 | device [ try "dmesg" if you don't see anything ] and should show up in | |
89 | /proc/devices. If not.... some changers use ID ? / LUN 0 for the | |
90 | device and ID ? / LUN 1 for the robot mechanism. But Linux does *not* | |
91 | look for LUN's other than 0 as default, becauce there are to many | |
92 | broken devices. So you can try: | |
93 | ||
94 | 1) echo "scsi add-single-device 0 0 ID 1" > /proc/scsi/scsi | |
95 | (replace ID with the SCSI-ID of the device) | |
96 | 2) boot the kernel with "max_scsi_luns=1" on the command line | |
97 | (append="max_scsi_luns=1" in lilo.conf should do the trick) | |
98 | ||
99 | ||
100 | Trouble? | |
101 | -------- | |
102 | ||
103 | If you insmod the driver with "insmod debug=1", it will be verbose and | |
104 | prints a lot of stuff to the syslog. Compiling the kernel with | |
105 | CONFIG_SCSI_CONSTANTS=y improves the quality of the error messages alot | |
106 | because the kernel will translate the error codes into human-readable | |
107 | strings then. | |
108 | ||
109 | You can display these messages with the dmesg command (or check the | |
110 | logfiles). If you email me some question becauce of a problem with the | |
111 | driver, please include these messages. | |
112 | ||
113 | ||
114 | Insmod options | |
115 | -------------- | |
116 | ||
117 | debug=0/1 | |
118 | Enable debug messages (see above, default: 0). | |
119 | ||
120 | verbose=0/1 | |
121 | Be verbose (default: 1). | |
122 | ||
123 | init=0/1 | |
124 | Send INITIALIZE ELEMENT STATUS command to the changer | |
125 | at insmod time (default: 1). | |
126 | ||
127 | timeout_init=<seconds> | |
128 | timeout for the INITIALIZE ELEMENT STATUS command | |
129 | (default: 3600). | |
130 | ||
131 | timeout_move=<seconds> | |
132 | timeout for all other commands (default: 120). | |
133 | ||
134 | dt_id=<id1>,<id2>,... | |
135 | dt_lun=<lun1>,<lun2>,... | |
136 | These two allow to specify the SCSI ID and LUN for the data | |
137 | transfer elements. You likely don't need this as the jukebox | |
138 | should provide this information. But some devices don't ... | |
139 | ||
140 | vendor_firsts= | |
141 | vendor_counts= | |
142 | vendor_labels= | |
143 | These insmod options can be used to tell the driver that there | |
144 | are some vendor-specific element types. Grundig for example | |
145 | does this. Some jukeboxes have a printer to label fresh burned | |
146 | CDs, which is addressed as element 0xc000 (type 5). To tell the | |
147 | driver about this vendor-specific element, use this: | |
148 | $ insmod ch \ | |
149 | vendor_firsts=0xc000 \ | |
150 | vendor_counts=1 \ | |
151 | vendor_labels=printer | |
152 | All three insmod options accept up to four comma-separated | |
153 | values, this way you can configure the element types 5-8. | |
154 | You likely need the SCSI specs for the device in question to | |
155 | find the correct values as they are not covered by the SCSI-2 | |
156 | standard. | |
157 | ||
158 | ||
159 | Credits | |
160 | ------- | |
161 | ||
162 | I wrote this driver using the famous mailing-patches-around-the-world | |
163 | method. With (more or less) help from: | |
164 | ||
165 | Daniel Moehwald <moehwald@hdg.de> | |
166 | Dane Jasper <dane@sonic.net> | |
167 | R. Scott Bailey <sbailey@dsddi.eds.com> | |
168 | Jonathan Corbet <corbet@lwn.net> | |
169 | ||
170 | Special thanks go to | |
171 | Martin Kuehne <martin.kuehne@bnbt.de> | |
172 | for a old, second-hand (but full functional) cdrom jukebox which I use | |
173 | to develop/test driver and tools now. | |
174 | ||
175 | Have fun, | |
176 | ||
177 | Gerd | |
178 | ||
179 | -- | |
180 | Gerd Knorr <kraxel@bytesex.org> |