| |
| README for the SCSI media changer driver |
| ======================================== |
| |
| This is a driver for SCSI Medium Changer devices, which are listed |
| with "Type: Medium Changer" in /proc/scsi/scsi. |
| |
| This is for *real* Jukeboxes. It is *not* supported to work with |
| common small CD-ROM changers, neither one-lun-per-slot SCSI changers |
| nor IDE drives. |
| |
| Userland tools available from here: |
| http://linux.bytesex.org/misc/changer.html |
| |
| |
| General Information |
| ------------------- |
| |
| First some words about how changers work: A changer has 2 (possibly |
| more) SCSI ID's. One for the changer device which controls the robot, |
| and one for the device which actually reads and writes the data. The |
| later may be anything, a MOD, a CD-ROM, a tape or whatever. For the |
| changer device this is a "don't care", he *only* shuffles around the |
| media, nothing else. |
| |
| |
| The SCSI changer model is complex, compared to - for example - IDE-CD |
| changers. But it allows to handle nearly all possible cases. It knows |
| 4 different types of changer elements: |
| |
| media transport - this one shuffles around the media, i.e. the |
| transport arm. Also known as "picker". |
| storage - a slot which can hold a media. |
| import/export - the same as above, but is accessible from outside, |
| i.e. there the operator (you !) can use this to |
| fill in and remove media from the changer. |
| Sometimes named "mailslot". |
| data transfer - this is the device which reads/writes, i.e. the |
| CD-ROM / Tape / whatever drive. |
| |
| None of these is limited to one: A huge Jukebox could have slots for |
| 123 CD-ROM's, 5 CD-ROM readers (and therefore 6 SCSI ID's: the changer |
| and each CD-ROM) and 2 transport arms. No problem to handle. |
| |
| |
| How it is implemented |
| --------------------- |
| |
| I implemented the driver as character device driver with a NetBSD-like |
| ioctl interface. Just grabbed NetBSD's header file and one of the |
| other linux SCSI device drivers as starting point. The interface |
| should be source code compatible with NetBSD. So if there is any |
| software (anybody knows ???) which supports a BSDish changer driver, |
| it should work with this driver too. |
| |
| Over time a few more ioctls where added, volume tag support for example |
| wasn't covered by the NetBSD ioctl API. |
| |
| |
| Current State |
| ------------- |
| |
| Support for more than one transport arm is not implemented yet (and |
| nobody asked for it so far...). |
| |
| I test and use the driver myself with a 35 slot cdrom jukebox from |
| Grundig. I got some reports telling it works ok with tape autoloaders |
| (Exabyte, HP and DEC). Some People use this driver with amanda. It |
| works fine with small (11 slots) and a huge (4 MOs, 88 slots) |
| magneto-optical Jukebox. Probably with lots of other changers too, most |
| (but not all :-) people mail me only if it does *not* work... |
| |
| I don't have any device lists, neither black-list nor white-list. Thus |
| it is quite useless to ask me whenever a specific device is supported or |
| not. In theory every changer device which supports the SCSI-2 media |
| changer command set should work out-of-the-box with this driver. If it |
| doesn't, it is a bug. Either within the driver or within the firmware |
| of the changer device. |
| |
| |
| Using it |
| -------- |
| |
| This is a character device with major number is 86, so use |
| "mknod /dev/sch0 c 86 0" to create the special file for the driver. |
| |
| If the module finds the changer, it prints some messages about the |
| device [ try "dmesg" if you don't see anything ] and should show up in |
| /proc/devices. If not.... some changers use ID ? / LUN 0 for the |
| device and ID ? / LUN 1 for the robot mechanism. But Linux does *not* |
| look for LUNs other than 0 as default, because there are too many |
| broken devices. So you can try: |
| |
| 1) echo "scsi add-single-device 0 0 ID 1" > /proc/scsi/scsi |
| (replace ID with the SCSI-ID of the device) |
| 2) boot the kernel with "max_scsi_luns=1" on the command line |
| (append="max_scsi_luns=1" in lilo.conf should do the trick) |
| |
| |
| Trouble? |
| -------- |
| |
| If you insmod the driver with "insmod debug=1", it will be verbose and |
| prints a lot of stuff to the syslog. Compiling the kernel with |
| CONFIG_SCSI_CONSTANTS=y improves the quality of the error messages a lot |
| because the kernel will translate the error codes into human-readable |
| strings then. |
| |
| You can display these messages with the dmesg command (or check the |
| logfiles). If you email me some question because of a problem with the |
| driver, please include these messages. |
| |
| |
| Insmod options |
| -------------- |
| |
| debug=0/1 |
| Enable debug messages (see above, default: 0). |
| |
| verbose=0/1 |
| Be verbose (default: 1). |
| |
| init=0/1 |
| Send INITIALIZE ELEMENT STATUS command to the changer |
| at insmod time (default: 1). |
| |
| timeout_init=<seconds> |
| timeout for the INITIALIZE ELEMENT STATUS command |
| (default: 3600). |
| |
| timeout_move=<seconds> |
| timeout for all other commands (default: 120). |
| |
| dt_id=<id1>,<id2>,... |
| dt_lun=<lun1>,<lun2>,... |
| These two allow to specify the SCSI ID and LUN for the data |
| transfer elements. You likely don't need this as the jukebox |
| should provide this information. But some devices don't ... |
| |
| vendor_firsts= |
| vendor_counts= |
| vendor_labels= |
| These insmod options can be used to tell the driver that there |
| are some vendor-specific element types. Grundig for example |
| does this. Some jukeboxes have a printer to label fresh burned |
| CDs, which is addressed as element 0xc000 (type 5). To tell the |
| driver about this vendor-specific element, use this: |
| $ insmod ch \ |
| vendor_firsts=0xc000 \ |
| vendor_counts=1 \ |
| vendor_labels=printer |
| All three insmod options accept up to four comma-separated |
| values, this way you can configure the element types 5-8. |
| You likely need the SCSI specs for the device in question to |
| find the correct values as they are not covered by the SCSI-2 |
| standard. |
| |
| |
| Credits |
| ------- |
| |
| I wrote this driver using the famous mailing-patches-around-the-world |
| method. With (more or less) help from: |
| |
| Daniel Moehwald <[email protected]> |
| Dane Jasper <[email protected]> |
| R. Scott Bailey <[email protected]> |
| Jonathan Corbet <[email protected]> |
| |
| Special thanks go to |
| Martin Kuehne <[email protected]> |
| for a old, second-hand (but full functional) cdrom jukebox which I use |
| to develop/test driver and tools now. |
| |
| Have fun, |
| |
| Gerd |
| |
| -- |
| Gerd Knorr <[email protected]> |
