1 .. SPDX-License-Identifier: GPL-2.0 2 3 ========================= 4 SCSI media changer driver 5 ========================= 6 7 This is a driver for SCSI Medium Changer devices, which are listed 8 with "Type: Medium Changer" in /proc/scsi/scsi. 9 10 This is for *real* Jukeboxes. It is *not* supported to work with 11 common small CD-ROM changers, neither one-lun-per-slot SCSI changers 12 nor IDE drives. 13 14 Userland tools available from here: 15 http://linux.bytesex.org/misc/changer.html 16 17 18 General Information 19 ------------------- 20 21 First some words about how changers work: A changer has 2 (possibly 22 more) SCSI ID's. One for the changer device which controls the robot, 23 and one for the device which actually reads and writes the data. The 24 later may be anything, a MOD, a CD-ROM, a tape or whatever. For the 25 changer device this is a "don't care", he *only* shuffles around the 26 media, nothing else. 27 28 29 The SCSI changer model is complex, compared to - for example - IDE-CD 30 changers. But it allows to handle nearly all possible cases. It knows 31 4 different types of changer elements: 32 33 =============== ================================================== 34 media transport this one shuffles around the media, i.e. the 35 transport arm. Also known as "picker". 36 storage a slot which can hold a media. 37 import/export the same as above, but is accessible from outside, 38 i.e. there the operator (you !) can use this to 39 fill in and remove media from the changer. 40 Sometimes named "mailslot". 41 data transfer this is the device which reads/writes, i.e. the 42 CD-ROM / Tape / whatever drive. 43 =============== ================================================== 44 45 None of these is limited to one: A huge Jukebox could have slots for 46 123 CD-ROM's, 5 CD-ROM readers (and therefore 6 SCSI ID's: the changer 47 and each CD-ROM) and 2 transport arms. No problem to handle. 48 49 50 How it is implemented 51 --------------------- 52 53 I implemented the driver as character device driver with a NetBSD-like 54 ioctl interface. Just grabbed NetBSD's header file and one of the 55 other linux SCSI device drivers as starting point. The interface 56 should be source code compatible with NetBSD. So if there is any 57 software (anybody knows ???) which supports a BSDish changer driver, 58 it should work with this driver too. 59 60 Over time a few more ioctls where added, volume tag support for example 61 wasn't covered by the NetBSD ioctl API. 62 63 64 Current State 65 ------------- 66 67 Support for more than one transport arm is not implemented yet (and 68 nobody asked for it so far...). 69 70 I test and use the driver myself with a 35 slot cdrom jukebox from 71 Grundig. I got some reports telling it works ok with tape autoloaders 72 (Exabyte, HP and DEC). Some People use this driver with amanda. It 73 works fine with small (11 slots) and a huge (4 MOs, 88 slots) 74 magneto-optical Jukebox. Probably with lots of other changers too, most 75 (but not all :-) people mail me only if it does *not* work... 76 77 I don't have any device lists, neither black-list nor white-list. Thus 78 it is quite useless to ask me whenever a specific device is supported or 79 not. In theory every changer device which supports the SCSI-2 media 80 changer command set should work out-of-the-box with this driver. If it 81 doesn't, it is a bug. Either within the driver or within the firmware 82 of the changer device. 83 84 85 Using it 86 -------- 87 88 This is a character device with major number is 86, so use 89 "mknod /dev/sch0 c 86 0" to create the special file for the driver. 90 91 If the module finds the changer, it prints some messages about the 92 device [ try "dmesg" if you don't see anything ] and should show up in 93 /proc/devices. If not.... some changers use ID ? / LUN 0 for the 94 device and ID ? / LUN 1 for the robot mechanism. But Linux does *not* 95 look for LUNs other than 0 as default, because there are too many 96 broken devices. So you can try: 97 98 1) echo "scsi add-single-device 0 0 ID 1" > /proc/scsi/scsi 99 (replace ID with the SCSI-ID of the device) 100 2) boot the kernel with "max_scsi_luns=1" on the command line 101 (append="max_scsi_luns=1" in lilo.conf should do the trick) 102 103 104 Trouble? 105 -------- 106 107 If you insmod the driver with "insmod debug=1", it will be verbose and 108 prints a lot of stuff to the syslog. Compiling the kernel with 109 CONFIG_SCSI_CONSTANTS=y improves the quality of the error messages a lot 110 because the kernel will translate the error codes into human-readable 111 strings then. 112 113 You can display these messages with the dmesg command (or check the 114 logfiles). If you email me some question because of a problem with the 115 driver, please include these messages. 116 117 118 Insmod options 119 -------------- 120 121 debug=0/1 122 Enable debug messages (see above, default: 0). 123 124 verbose=0/1 125 Be verbose (default: 1). 126 127 init=0/1 128 Send INITIALIZE ELEMENT STATUS command to the changer 129 at insmod time (default: 1). 130 131 timeout_init=<seconds> 132 timeout for the INITIALIZE ELEMENT STATUS command 133 (default: 3600). 134 135 timeout_move=<seconds> 136 timeout for all other commands (default: 120). 137 138 dt_id=<id1>,<id2>,... / dt_lun=<lun1>,<lun2>,... 139 These two allow to specify the SCSI ID and LUN for the data 140 transfer elements. You likely don't need this as the jukebox 141 should provide this information. But some devices don't ... 142 143 vendor_firsts=, vendor_counts=, vendor_labels= 144 These insmod options can be used to tell the driver that there 145 are some vendor-specific element types. Grundig for example 146 does this. Some jukeboxes have a printer to label fresh burned 147 CDs, which is addressed as element 0xc000 (type 5). To tell the 148 driver about this vendor-specific element, use this:: 149 150 $ insmod ch \ 151 vendor_firsts=0xc000 \ 152 vendor_counts=1 \ 153 vendor_labels=printer 154 155 All three insmod options accept up to four comma-separated 156 values, this way you can configure the element types 5-8. 157 You likely need the SCSI specs for the device in question to 158 find the correct values as they are not covered by the SCSI-2 159 standard. 160 161 162 Credits 163 ------- 164 165 I wrote this driver using the famous mailing-patches-around-the-world 166 method. With (more or less) help from: 167 168 - Daniel Moehwald <moehwald@hdg.de> 169 - Dane Jasper <dane@sonic.net> 170 - R. Scott Bailey <sbailey@dsddi.eds.com> 171 - Jonathan Corbet <corbet@lwn.net> 172 173 Special thanks go to 174 175 - Martin Kuehne <martin.kuehne@bnbt.de> 176 177 for a old, second-hand (but full functional) cdrom jukebox which I use 178 to develop/test driver and tools now. 179 180 Have fun, 181 182 Gerd 183 184 Gerd Knorr <kraxel@bytesex.org>
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