1 2README for the SCSI media changer driver 3======================================== 4 5This is a driver for SCSI Medium Changer devices, which are listed 6with "Type: Medium Changer" in /proc/scsi/scsi. 7 8This is for *real* Jukeboxes. It is *not* supported to work with 9common small CD-ROM changers, neither one-lun-per-slot SCSI changers 10nor IDE drives. 11 12Userland tools available from here: 13 http://linux.bytesex.org/misc/changer.html 14 15 16General Information 17------------------- 18 19First some words about how changers work: A changer has 2 (possibly 20more) SCSI ID's. One for the changer device which controls the robot, 21and one for the device which actually reads and writes the data. The 22later may be anything, a MOD, a CD-ROM, a tape or whatever. For the 23changer device this is a "don't care", he *only* shuffles around the 24media, nothing else. 25 26 27The SCSI changer model is complex, compared to - for example - IDE-CD 28changers. But it allows to handle nearly all possible cases. It knows 294 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 accessible 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 41None of these is limited to one: A huge Jukebox could have slots for 42123 CD-ROM's, 5 CD-ROM readers (and therefore 6 SCSI ID's: the changer 43and each CD-ROM) and 2 transport arms. No problem to handle. 44 45 46How it is implemented 47--------------------- 48 49I implemented the driver as character device driver with a NetBSD-like 50ioctl interface. Just grabbed NetBSD's header file and one of the 51other linux SCSI device drivers as starting point. The interface 52should be source code compatible with NetBSD. So if there is any 53software (anybody knows ???) which supports a BSDish changer driver, 54it should work with this driver too. 55 56Over time a few more ioctls where added, volume tag support for example 57wasn't covered by the NetBSD ioctl API. 58 59 60Current State 61------------- 62 63Support for more than one transport arm is not implemented yet (and 64nobody asked for it so far...). 65 66I test and use the driver myself with a 35 slot cdrom jukebox from 67Grundig. I got some reports telling it works ok with tape autoloaders 68(Exabyte, HP and DEC). Some People use this driver with amanda. It 69works fine with small (11 slots) and a huge (4 MOs, 88 slots) 70magneto-optical Jukebox. Probably with lots of other changers too, most 71(but not all :-) people mail me only if it does *not* work... 72 73I don't have any device lists, neither black-list nor white-list. Thus 74it is quite useless to ask me whenever a specific device is supported or 75not. In theory every changer device which supports the SCSI-2 media 76changer command set should work out-of-the-box with this driver. If it 77doesn't, it is a bug. Either within the driver or within the firmware 78of the changer device. 79 80 81Using it 82-------- 83 84This 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 87If the module finds the changer, it prints some messages about the 88device [ 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 90device and ID ? / LUN 1 for the robot mechanism. But Linux does *not* 91look for LUNs other than 0 as default, because there are too many 92broken 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 100Trouble? 101-------- 102 103If you insmod the driver with "insmod debug=1", it will be verbose and 104prints a lot of stuff to the syslog. Compiling the kernel with 105CONFIG_SCSI_CONSTANTS=y improves the quality of the error messages a lot 106because the kernel will translate the error codes into human-readable 107strings then. 108 109You can display these messages with the dmesg command (or check the 110logfiles). If you email me some question because of a problem with the 111driver, please include these messages. 112 113 114Insmod options 115-------------- 116 117debug=0/1 118 Enable debug messages (see above, default: 0). 119 120verbose=0/1 121 Be verbose (default: 1). 122 123init=0/1 124 Send INITIALIZE ELEMENT STATUS command to the changer 125 at insmod time (default: 1). 126 127timeout_init=<seconds> 128 timeout for the INITIALIZE ELEMENT STATUS command 129 (default: 3600). 130 131timeout_move=<seconds> 132 timeout for all other commands (default: 120). 133 134dt_id=<id1>,<id2>,... 135dt_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 140vendor_firsts= 141vendor_counts= 142vendor_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 159Credits 160------- 161 162I wrote this driver using the famous mailing-patches-around-the-world 163method. 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 170Special thanks go to 171 Martin Kuehne <martin.kuehne@bnbt.de> 172for a old, second-hand (but full functional) cdrom jukebox which I use 173to develop/test driver and tools now. 174 175Have fun, 176 177 Gerd 178 179-- 180Gerd Knorr <kraxel@bytesex.org> 181