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1 | |||
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> | ||