1*bf65c846SMauro Carvalho Chehab.. SPDX-License-Identifier: GPL-2.0 2*bf65c846SMauro Carvalho Chehab 3*bf65c846SMauro Carvalho Chehab==================== 4*bf65c846SMauro Carvalho ChehabThe SCSI Tape Driver 5*bf65c846SMauro Carvalho Chehab==================== 6*bf65c846SMauro Carvalho Chehab 7*bf65c846SMauro Carvalho ChehabThis file contains brief information about the SCSI tape driver. 8*bf65c846SMauro Carvalho ChehabThe driver is currently maintained by Kai Mäkisara (email 9*bf65c846SMauro Carvalho ChehabKai.Makisara@kolumbus.fi) 10*bf65c846SMauro Carvalho Chehab 11*bf65c846SMauro Carvalho ChehabLast modified: Tue Feb 9 21:54:16 2016 by kai.makisara 12*bf65c846SMauro Carvalho Chehab 13*bf65c846SMauro Carvalho Chehab 14*bf65c846SMauro Carvalho ChehabBasics 15*bf65c846SMauro Carvalho Chehab====== 16*bf65c846SMauro Carvalho Chehab 17*bf65c846SMauro Carvalho ChehabThe driver is generic, i.e., it does not contain any code tailored 18*bf65c846SMauro Carvalho Chehabto any specific tape drive. The tape parameters can be specified with 19*bf65c846SMauro Carvalho Chehabone of the following three methods: 20*bf65c846SMauro Carvalho Chehab 21*bf65c846SMauro Carvalho Chehab1. Each user can specify the tape parameters he/she wants to use 22*bf65c846SMauro Carvalho Chehabdirectly with ioctls. This is administratively a very simple and 23*bf65c846SMauro Carvalho Chehabflexible method and applicable to single-user workstations. However, 24*bf65c846SMauro Carvalho Chehabin a multiuser environment the next user finds the tape parameters in 25*bf65c846SMauro Carvalho Chehabstate the previous user left them. 26*bf65c846SMauro Carvalho Chehab 27*bf65c846SMauro Carvalho Chehab2. The system manager (root) can define default values for some tape 28*bf65c846SMauro Carvalho Chehabparameters, like block size and density using the MTSETDRVBUFFER ioctl. 29*bf65c846SMauro Carvalho ChehabThese parameters can be programmed to come into effect either when a 30*bf65c846SMauro Carvalho Chehabnew tape is loaded into the drive or if writing begins at the 31*bf65c846SMauro Carvalho Chehabbeginning of the tape. The second method is applicable if the tape 32*bf65c846SMauro Carvalho Chehabdrive performs auto-detection of the tape format well (like some 33*bf65c846SMauro Carvalho ChehabQIC-drives). The result is that any tape can be read, writing can be 34*bf65c846SMauro Carvalho Chehabcontinued using existing format, and the default format is used if 35*bf65c846SMauro Carvalho Chehabthe tape is rewritten from the beginning (or a new tape is written 36*bf65c846SMauro Carvalho Chehabfor the first time). The first method is applicable if the drive 37*bf65c846SMauro Carvalho Chehabdoes not perform auto-detection well enough and there is a single 38*bf65c846SMauro Carvalho Chehab"sensible" mode for the device. An example is a DAT drive that is 39*bf65c846SMauro Carvalho Chehabused only in variable block mode (I don't know if this is sensible 40*bf65c846SMauro Carvalho Chehabor not :-). 41*bf65c846SMauro Carvalho Chehab 42*bf65c846SMauro Carvalho ChehabThe user can override the parameters defined by the system 43*bf65c846SMauro Carvalho Chehabmanager. The changes persist until the defaults again come into 44*bf65c846SMauro Carvalho Chehabeffect. 45*bf65c846SMauro Carvalho Chehab 46*bf65c846SMauro Carvalho Chehab3. By default, up to four modes can be defined and selected using the minor 47*bf65c846SMauro Carvalho Chehabnumber (bits 5 and 6). The number of modes can be changed by changing 48*bf65c846SMauro Carvalho ChehabST_NBR_MODE_BITS in st.h. Mode 0 corresponds to the defaults discussed 49*bf65c846SMauro Carvalho Chehababove. Additional modes are dormant until they are defined by the 50*bf65c846SMauro Carvalho Chehabsystem manager (root). When specification of a new mode is started, 51*bf65c846SMauro Carvalho Chehabthe configuration of mode 0 is used to provide a starting point for 52*bf65c846SMauro Carvalho Chehabdefinition of the new mode. 53*bf65c846SMauro Carvalho Chehab 54*bf65c846SMauro Carvalho ChehabUsing the modes allows the system manager to give the users choices 55*bf65c846SMauro Carvalho Chehabover some of the buffering parameters not directly accessible to the 56*bf65c846SMauro Carvalho Chehabusers (buffered and asynchronous writes). The modes also allow choices 57*bf65c846SMauro Carvalho Chehabbetween formats in multi-tape operations (the explicitly overridden 58*bf65c846SMauro Carvalho Chehabparameters are reset when a new tape is loaded). 59*bf65c846SMauro Carvalho Chehab 60*bf65c846SMauro Carvalho ChehabIf more than one mode is used, all modes should contain definitions 61*bf65c846SMauro Carvalho Chehabfor the same set of parameters. 62*bf65c846SMauro Carvalho Chehab 63*bf65c846SMauro Carvalho ChehabMany Unices contain internal tables that associate different modes to 64*bf65c846SMauro Carvalho Chehabsupported devices. The Linux SCSI tape driver does not contain such 65*bf65c846SMauro Carvalho Chehabtables (and will not do that in future). Instead of that, a utility 66*bf65c846SMauro Carvalho Chehabprogram can be made that fetches the inquiry data sent by the device, 67*bf65c846SMauro Carvalho Chehabscans its database, and sets up the modes using the ioctls. Another 68*bf65c846SMauro Carvalho Chehabalternative is to make a small script that uses mt to set the defaults 69*bf65c846SMauro Carvalho Chehabtailored to the system. 70*bf65c846SMauro Carvalho Chehab 71*bf65c846SMauro Carvalho ChehabThe driver supports fixed and variable block size (within buffer 72*bf65c846SMauro Carvalho Chehablimits). Both the auto-rewind (minor equals device number) and 73*bf65c846SMauro Carvalho Chehabnon-rewind devices (minor is 128 + device number) are implemented. 74*bf65c846SMauro Carvalho Chehab 75*bf65c846SMauro Carvalho ChehabIn variable block mode, the byte count in write() determines the size 76*bf65c846SMauro Carvalho Chehabof the physical block on tape. When reading, the drive reads the next 77*bf65c846SMauro Carvalho Chehabtape block and returns to the user the data if the read() byte count 78*bf65c846SMauro Carvalho Chehabis at least the block size. Otherwise, error ENOMEM is returned. 79*bf65c846SMauro Carvalho Chehab 80*bf65c846SMauro Carvalho ChehabIn fixed block mode, the data transfer between the drive and the 81*bf65c846SMauro Carvalho Chehabdriver is in multiples of the block size. The write() byte count must 82*bf65c846SMauro Carvalho Chehabbe a multiple of the block size. This is not required when reading but 83*bf65c846SMauro Carvalho Chehabmay be advisable for portability. 84*bf65c846SMauro Carvalho Chehab 85*bf65c846SMauro Carvalho ChehabSupport is provided for changing the tape partition and partitioning 86*bf65c846SMauro Carvalho Chehabof the tape with one or two partitions. By default support for 87*bf65c846SMauro Carvalho Chehabpartitioned tape is disabled for each driver and it can be enabled 88*bf65c846SMauro Carvalho Chehabwith the ioctl MTSETDRVBUFFER. 89*bf65c846SMauro Carvalho Chehab 90*bf65c846SMauro Carvalho ChehabBy default the driver writes one filemark when the device is closed after 91*bf65c846SMauro Carvalho Chehabwriting and the last operation has been a write. Two filemarks can be 92*bf65c846SMauro Carvalho Chehaboptionally written. In both cases end of data is signified by 93*bf65c846SMauro Carvalho Chehabreturning zero bytes for two consecutive reads. 94*bf65c846SMauro Carvalho Chehab 95*bf65c846SMauro Carvalho ChehabWriting filemarks without the immediate bit set in the SCSI command block acts 96*bf65c846SMauro Carvalho Chehabas a synchronization point, i.e., all remaining data form the drive buffers is 97*bf65c846SMauro Carvalho Chehabwritten to tape before the command returns. This makes sure that write errors 98*bf65c846SMauro Carvalho Chehabare caught at that point, but this takes time. In some applications, several 99*bf65c846SMauro Carvalho Chehabconsecutive files must be written fast. The MTWEOFI operation can be used to 100*bf65c846SMauro Carvalho Chehabwrite the filemarks without flushing the drive buffer. Writing filemark at 101*bf65c846SMauro Carvalho Chehabclose() is always flushing the drive buffers. However, if the previous 102*bf65c846SMauro Carvalho Chehaboperation is MTWEOFI, close() does not write a filemark. This can be used if 103*bf65c846SMauro Carvalho Chehabthe program wants to close/open the tape device between files and wants to 104*bf65c846SMauro Carvalho Chehabskip waiting. 105*bf65c846SMauro Carvalho Chehab 106*bf65c846SMauro Carvalho ChehabIf rewind, offline, bsf, or seek is done and previous tape operation was 107*bf65c846SMauro Carvalho Chehabwrite, a filemark is written before moving tape. 108*bf65c846SMauro Carvalho Chehab 109*bf65c846SMauro Carvalho ChehabThe compile options are defined in the file linux/drivers/scsi/st_options.h. 110*bf65c846SMauro Carvalho Chehab 111*bf65c846SMauro Carvalho Chehab4. If the open option O_NONBLOCK is used, open succeeds even if the 112*bf65c846SMauro Carvalho Chehabdrive is not ready. If O_NONBLOCK is not used, the driver waits for 113*bf65c846SMauro Carvalho Chehabthe drive to become ready. If this does not happen in ST_BLOCK_SECONDS 114*bf65c846SMauro Carvalho Chehabseconds, open fails with the errno value EIO. With O_NONBLOCK the 115*bf65c846SMauro Carvalho Chehabdevice can be opened for writing even if there is a write protected 116*bf65c846SMauro Carvalho Chehabtape in the drive (commands trying to write something return error if 117*bf65c846SMauro Carvalho Chehabattempted). 118*bf65c846SMauro Carvalho Chehab 119*bf65c846SMauro Carvalho Chehab 120*bf65c846SMauro Carvalho ChehabMinor Numbers 121*bf65c846SMauro Carvalho Chehab============= 122*bf65c846SMauro Carvalho Chehab 123*bf65c846SMauro Carvalho ChehabThe tape driver currently supports up to 2^17 drives if 4 modes for 124*bf65c846SMauro Carvalho Chehabeach drive are used. 125*bf65c846SMauro Carvalho Chehab 126*bf65c846SMauro Carvalho ChehabThe minor numbers consist of the following bit fields:: 127*bf65c846SMauro Carvalho Chehab 128*bf65c846SMauro Carvalho Chehab dev_upper non-rew mode dev-lower 129*bf65c846SMauro Carvalho Chehab 20 - 8 7 6 5 4 0 130*bf65c846SMauro Carvalho Chehab 131*bf65c846SMauro Carvalho ChehabThe non-rewind bit is always bit 7 (the uppermost bit in the lowermost 132*bf65c846SMauro Carvalho Chehabbyte). The bits defining the mode are below the non-rewind bit. The 133*bf65c846SMauro Carvalho Chehabremaining bits define the tape device number. This numbering is 134*bf65c846SMauro Carvalho Chehabbackward compatible with the numbering used when the minor number was 135*bf65c846SMauro Carvalho Chehabonly 8 bits wide. 136*bf65c846SMauro Carvalho Chehab 137*bf65c846SMauro Carvalho Chehab 138*bf65c846SMauro Carvalho ChehabSysfs Support 139*bf65c846SMauro Carvalho Chehab============= 140*bf65c846SMauro Carvalho Chehab 141*bf65c846SMauro Carvalho ChehabThe driver creates the directory /sys/class/scsi_tape and populates it with 142*bf65c846SMauro Carvalho Chehabdirectories corresponding to the existing tape devices. There are autorewind 143*bf65c846SMauro Carvalho Chehaband non-rewind entries for each mode. The names are stxy and nstxy, where x 144*bf65c846SMauro Carvalho Chehabis the tape number and y a character corresponding to the mode (none, l, m, 145*bf65c846SMauro Carvalho Chehaba). For example, the directories for the first tape device are (assuming four 146*bf65c846SMauro Carvalho Chehabmodes): st0 nst0 st0l nst0l st0m nst0m st0a nst0a. 147*bf65c846SMauro Carvalho Chehab 148*bf65c846SMauro Carvalho ChehabEach directory contains the entries: default_blksize default_compression 149*bf65c846SMauro Carvalho Chehabdefault_density defined dev device driver. The file 'defined' contains 1 150*bf65c846SMauro Carvalho Chehabif the mode is defined and zero if not defined. The files 'default_*' contain 151*bf65c846SMauro Carvalho Chehabthe defaults set by the user. The value -1 means the default is not set. The 152*bf65c846SMauro Carvalho Chehabfile 'dev' contains the device numbers corresponding to this device. The links 153*bf65c846SMauro Carvalho Chehab'device' and 'driver' point to the SCSI device and driver entries. 154*bf65c846SMauro Carvalho Chehab 155*bf65c846SMauro Carvalho ChehabEach directory also contains the entry 'options' which shows the currently 156*bf65c846SMauro Carvalho Chehabenabled driver and mode options. The value in the file is a bit mask where the 157*bf65c846SMauro Carvalho Chehabbit definitions are the same as those used with MTSETDRVBUFFER in setting the 158*bf65c846SMauro Carvalho Chehaboptions. 159*bf65c846SMauro Carvalho Chehab 160*bf65c846SMauro Carvalho ChehabA link named 'tape' is made from the SCSI device directory to the class 161*bf65c846SMauro Carvalho Chehabdirectory corresponding to the mode 0 auto-rewind device (e.g., st0). 162*bf65c846SMauro Carvalho Chehab 163*bf65c846SMauro Carvalho Chehab 164*bf65c846SMauro Carvalho ChehabSysfs and Statistics for Tape Devices 165*bf65c846SMauro Carvalho Chehab===================================== 166*bf65c846SMauro Carvalho Chehab 167*bf65c846SMauro Carvalho ChehabThe st driver maintains statistics for tape drives inside the sysfs filesystem. 168*bf65c846SMauro Carvalho ChehabThe following method can be used to locate the statistics that are 169*bf65c846SMauro Carvalho Chehabavailable (assuming that sysfs is mounted at /sys): 170*bf65c846SMauro Carvalho Chehab 171*bf65c846SMauro Carvalho Chehab1. Use opendir(3) on the directory /sys/class/scsi_tape 172*bf65c846SMauro Carvalho Chehab2. Use readdir(3) to read the directory contents 173*bf65c846SMauro Carvalho Chehab3. Use regcomp(3)/regexec(3) to match directory entries to the extended 174*bf65c846SMauro Carvalho Chehab regular expression "^st[0-9]+$" 175*bf65c846SMauro Carvalho Chehab4. Access the statistics from the /sys/class/scsi_tape/<match>/stats 176*bf65c846SMauro Carvalho Chehab directory (where <match> is a directory entry from /sys/class/scsi_tape 177*bf65c846SMauro Carvalho Chehab that matched the extended regular expression) 178*bf65c846SMauro Carvalho Chehab 179*bf65c846SMauro Carvalho ChehabThe reason for using this approach is that all the character devices 180*bf65c846SMauro Carvalho Chehabpointing to the same tape drive use the same statistics. That means 181*bf65c846SMauro Carvalho Chehabthat st0 would have the same statistics as nst0. 182*bf65c846SMauro Carvalho Chehab 183*bf65c846SMauro Carvalho ChehabThe directory contains the following statistics files: 184*bf65c846SMauro Carvalho Chehab 185*bf65c846SMauro Carvalho Chehab1. in_flight 186*bf65c846SMauro Carvalho Chehab - The number of I/Os currently outstanding to this device. 187*bf65c846SMauro Carvalho Chehab2. io_ns 188*bf65c846SMauro Carvalho Chehab - The amount of time spent waiting (in nanoseconds) for all I/O 189*bf65c846SMauro Carvalho Chehab to complete (including read and write). This includes tape movement 190*bf65c846SMauro Carvalho Chehab commands such as seeking between file or set marks and implicit tape 191*bf65c846SMauro Carvalho Chehab movement such as when rewind on close tape devices are used. 192*bf65c846SMauro Carvalho Chehab3. other_cnt 193*bf65c846SMauro Carvalho Chehab - The number of I/Os issued to the tape drive other than read or 194*bf65c846SMauro Carvalho Chehab write commands. The time taken to complete these commands uses the 195*bf65c846SMauro Carvalho Chehab following calculation io_ms-read_ms-write_ms. 196*bf65c846SMauro Carvalho Chehab4. read_byte_cnt 197*bf65c846SMauro Carvalho Chehab - The number of bytes read from the tape drive. 198*bf65c846SMauro Carvalho Chehab5. read_cnt 199*bf65c846SMauro Carvalho Chehab - The number of read requests issued to the tape drive. 200*bf65c846SMauro Carvalho Chehab6. read_ns 201*bf65c846SMauro Carvalho Chehab - The amount of time (in nanoseconds) spent waiting for read 202*bf65c846SMauro Carvalho Chehab requests to complete. 203*bf65c846SMauro Carvalho Chehab7. write_byte_cnt 204*bf65c846SMauro Carvalho Chehab - The number of bytes written to the tape drive. 205*bf65c846SMauro Carvalho Chehab8. write_cnt 206*bf65c846SMauro Carvalho Chehab - The number of write requests issued to the tape drive. 207*bf65c846SMauro Carvalho Chehab9. write_ns 208*bf65c846SMauro Carvalho Chehab - The amount of time (in nanoseconds) spent waiting for write 209*bf65c846SMauro Carvalho Chehab requests to complete. 210*bf65c846SMauro Carvalho Chehab10. resid_cnt 211*bf65c846SMauro Carvalho Chehab - The number of times during a read or write we found 212*bf65c846SMauro Carvalho Chehab the residual amount to be non-zero. This should mean that a program 213*bf65c846SMauro Carvalho Chehab is issuing a read larger thean the block size on tape. For write 214*bf65c846SMauro Carvalho Chehab not all data made it to tape. 215*bf65c846SMauro Carvalho Chehab 216*bf65c846SMauro Carvalho Chehab.. Note:: 217*bf65c846SMauro Carvalho Chehab 218*bf65c846SMauro Carvalho Chehab The in_flight value is incremented when an I/O starts the I/O 219*bf65c846SMauro Carvalho Chehab itself is not added to the statistics until it completes. 220*bf65c846SMauro Carvalho Chehab 221*bf65c846SMauro Carvalho ChehabThe total of read_cnt, write_cnt, and other_cnt may not total to the same 222*bf65c846SMauro Carvalho Chehabvalue as iodone_cnt at the device level. The tape statistics only count 223*bf65c846SMauro Carvalho ChehabI/O issued via the st module. 224*bf65c846SMauro Carvalho Chehab 225*bf65c846SMauro Carvalho ChehabWhen read the statistics may not be temporally consistent while I/O is in 226*bf65c846SMauro Carvalho Chehabprogress. The individual values are read and written to atomically however 227*bf65c846SMauro Carvalho Chehabwhen reading them back via sysfs they may be in the process of being 228*bf65c846SMauro Carvalho Chehabupdated when starting an I/O or when it is completed. 229*bf65c846SMauro Carvalho Chehab 230*bf65c846SMauro Carvalho ChehabThe value shown in in_flight is incremented before any statstics are 231*bf65c846SMauro Carvalho Chehabupdated and decremented when an I/O completes after updating statistics. 232*bf65c846SMauro Carvalho ChehabThe value of in_flight is 0 when there are no I/Os outstanding that are 233*bf65c846SMauro Carvalho Chehabissued by the st driver. Tape statistics do not take into account any 234*bf65c846SMauro Carvalho ChehabI/O performed via the sg device. 235*bf65c846SMauro Carvalho Chehab 236*bf65c846SMauro Carvalho ChehabBSD and Sys V Semantics 237*bf65c846SMauro Carvalho Chehab======================= 238*bf65c846SMauro Carvalho Chehab 239*bf65c846SMauro Carvalho ChehabThe user can choose between these two behaviours of the tape driver by 240*bf65c846SMauro Carvalho Chehabdefining the value of the symbol ST_SYSV. The semantics differ when a 241*bf65c846SMauro Carvalho Chehabfile being read is closed. The BSD semantics leaves the tape where it 242*bf65c846SMauro Carvalho Chehabcurrently is whereas the SYS V semantics moves the tape past the next 243*bf65c846SMauro Carvalho Chehabfilemark unless the filemark has just been crossed. 244*bf65c846SMauro Carvalho Chehab 245*bf65c846SMauro Carvalho ChehabThe default is BSD semantics. 246*bf65c846SMauro Carvalho Chehab 247*bf65c846SMauro Carvalho Chehab 248*bf65c846SMauro Carvalho ChehabBuffering 249*bf65c846SMauro Carvalho Chehab========= 250*bf65c846SMauro Carvalho Chehab 251*bf65c846SMauro Carvalho ChehabThe driver tries to do transfers directly to/from user space. If this 252*bf65c846SMauro Carvalho Chehabis not possible, a driver buffer allocated at run-time is used. If 253*bf65c846SMauro Carvalho Chehabdirect i/o is not possible for the whole transfer, the driver buffer 254*bf65c846SMauro Carvalho Chehabis used (i.e., bounce buffers for individual pages are not 255*bf65c846SMauro Carvalho Chehabused). Direct i/o can be impossible because of several reasons, e.g.: 256*bf65c846SMauro Carvalho Chehab 257*bf65c846SMauro Carvalho Chehab- one or more pages are at addresses not reachable by the HBA 258*bf65c846SMauro Carvalho Chehab- the number of pages in the transfer exceeds the number of 259*bf65c846SMauro Carvalho Chehab scatter/gather segments permitted by the HBA 260*bf65c846SMauro Carvalho Chehab- one or more pages can't be locked into memory (should not happen in 261*bf65c846SMauro Carvalho Chehab any reasonable situation) 262*bf65c846SMauro Carvalho Chehab 263*bf65c846SMauro Carvalho ChehabThe size of the driver buffers is always at least one tape block. In fixed 264*bf65c846SMauro Carvalho Chehabblock mode, the minimum buffer size is defined (in 1024 byte units) by 265*bf65c846SMauro Carvalho ChehabST_FIXED_BUFFER_BLOCKS. With small block size this allows buffering of 266*bf65c846SMauro Carvalho Chehabseveral blocks and using one SCSI read or write to transfer all of the 267*bf65c846SMauro Carvalho Chehabblocks. Buffering of data across write calls in fixed block mode is 268*bf65c846SMauro Carvalho Chehaballowed if ST_BUFFER_WRITES is non-zero and direct i/o is not used. 269*bf65c846SMauro Carvalho ChehabBuffer allocation uses chunks of memory having sizes 2^n * (page 270*bf65c846SMauro Carvalho Chehabsize). Because of this the actual buffer size may be larger than the 271*bf65c846SMauro Carvalho Chehabminimum allowable buffer size. 272*bf65c846SMauro Carvalho Chehab 273*bf65c846SMauro Carvalho ChehabNOTE that if direct i/o is used, the small writes are not buffered. This may 274*bf65c846SMauro Carvalho Chehabcause a surprise when moving from 2.4. There small writes (e.g., tar without 275*bf65c846SMauro Carvalho Chehab-b option) may have had good throughput but this is not true any more with 276*bf65c846SMauro Carvalho Chehab2.6. Direct i/o can be turned off to solve this problem but a better solution 277*bf65c846SMauro Carvalho Chehabis to use bigger write() byte counts (e.g., tar -b 64). 278*bf65c846SMauro Carvalho Chehab 279*bf65c846SMauro Carvalho ChehabAsynchronous writing. Writing the buffer contents to the tape is 280*bf65c846SMauro Carvalho Chehabstarted and the write call returns immediately. The status is checked 281*bf65c846SMauro Carvalho Chehabat the next tape operation. Asynchronous writes are not done with 282*bf65c846SMauro Carvalho Chehabdirect i/o and not in fixed block mode. 283*bf65c846SMauro Carvalho Chehab 284*bf65c846SMauro Carvalho ChehabBuffered writes and asynchronous writes may in some rare cases cause 285*bf65c846SMauro Carvalho Chehabproblems in multivolume operations if there is not enough space on the 286*bf65c846SMauro Carvalho Chehabtape after the early-warning mark to flush the driver buffer. 287*bf65c846SMauro Carvalho Chehab 288*bf65c846SMauro Carvalho ChehabRead ahead for fixed block mode (ST_READ_AHEAD). Filling the buffer is 289*bf65c846SMauro Carvalho Chehabattempted even if the user does not want to get all of the data at 290*bf65c846SMauro Carvalho Chehabthis read command. Should be disabled for those drives that don't like 291*bf65c846SMauro Carvalho Chehaba filemark to truncate a read request or that don't like backspacing. 292*bf65c846SMauro Carvalho Chehab 293*bf65c846SMauro Carvalho ChehabScatter/gather buffers (buffers that consist of chunks non-contiguous 294*bf65c846SMauro Carvalho Chehabin the physical memory) are used if contiguous buffers can't be 295*bf65c846SMauro Carvalho Chehaballocated. To support all SCSI adapters (including those not 296*bf65c846SMauro Carvalho Chehabsupporting scatter/gather), buffer allocation is using the following 297*bf65c846SMauro Carvalho Chehabthree kinds of chunks: 298*bf65c846SMauro Carvalho Chehab 299*bf65c846SMauro Carvalho Chehab1. The initial segment that is used for all SCSI adapters including 300*bf65c846SMauro Carvalho Chehab those not supporting scatter/gather. The size of this buffer will be 301*bf65c846SMauro Carvalho Chehab (PAGE_SIZE << ST_FIRST_ORDER) bytes if the system can give a chunk of 302*bf65c846SMauro Carvalho Chehab this size (and it is not larger than the buffer size specified by 303*bf65c846SMauro Carvalho Chehab ST_BUFFER_BLOCKS). If this size is not available, the driver halves 304*bf65c846SMauro Carvalho Chehab the size and tries again until the size of one page. The default 305*bf65c846SMauro Carvalho Chehab settings in st_options.h make the driver to try to allocate all of the 306*bf65c846SMauro Carvalho Chehab buffer as one chunk. 307*bf65c846SMauro Carvalho Chehab2. The scatter/gather segments to fill the specified buffer size are 308*bf65c846SMauro Carvalho Chehab allocated so that as many segments as possible are used but the number 309*bf65c846SMauro Carvalho Chehab of segments does not exceed ST_FIRST_SG. 310*bf65c846SMauro Carvalho Chehab3. The remaining segments between ST_MAX_SG (or the module parameter 311*bf65c846SMauro Carvalho Chehab max_sg_segs) and the number of segments used in phases 1 and 2 312*bf65c846SMauro Carvalho Chehab are used to extend the buffer at run-time if this is necessary. The 313*bf65c846SMauro Carvalho Chehab number of scatter/gather segments allowed for the SCSI adapter is not 314*bf65c846SMauro Carvalho Chehab exceeded if it is smaller than the maximum number of scatter/gather 315*bf65c846SMauro Carvalho Chehab segments specified. If the maximum number allowed for the SCSI adapter 316*bf65c846SMauro Carvalho Chehab is smaller than the number of segments used in phases 1 and 2, 317*bf65c846SMauro Carvalho Chehab extending the buffer will always fail. 318*bf65c846SMauro Carvalho Chehab 319*bf65c846SMauro Carvalho Chehab 320*bf65c846SMauro Carvalho ChehabEOM Behaviour When Writing 321*bf65c846SMauro Carvalho Chehab========================== 322*bf65c846SMauro Carvalho Chehab 323*bf65c846SMauro Carvalho ChehabWhen the end of medium early warning is encountered, the current write 324*bf65c846SMauro Carvalho Chehabis finished and the number of bytes is returned. The next write 325*bf65c846SMauro Carvalho Chehabreturns -1 and errno is set to ENOSPC. To enable writing a trailer, 326*bf65c846SMauro Carvalho Chehabthe next write is allowed to proceed and, if successful, the number of 327*bf65c846SMauro Carvalho Chehabbytes is returned. After this, -1 and the number of bytes are 328*bf65c846SMauro Carvalho Chehabalternately returned until the physical end of medium (or some other 329*bf65c846SMauro Carvalho Chehaberror) is encountered. 330*bf65c846SMauro Carvalho Chehab 331*bf65c846SMauro Carvalho ChehabModule Parameters 332*bf65c846SMauro Carvalho Chehab================= 333*bf65c846SMauro Carvalho Chehab 334*bf65c846SMauro Carvalho ChehabThe buffer size, write threshold, and the maximum number of allocated buffers 335*bf65c846SMauro Carvalho Chehabare configurable when the driver is loaded as a module. The keywords are: 336*bf65c846SMauro Carvalho Chehab 337*bf65c846SMauro Carvalho Chehab========================== =========================================== 338*bf65c846SMauro Carvalho Chehabbuffer_kbs=xxx the buffer size for fixed block mode is set 339*bf65c846SMauro Carvalho Chehab to xxx kilobytes 340*bf65c846SMauro Carvalho Chehabwrite_threshold_kbs=xxx the write threshold in kilobytes set to xxx 341*bf65c846SMauro Carvalho Chehabmax_sg_segs=xxx the maximum number of scatter/gather 342*bf65c846SMauro Carvalho Chehab segments 343*bf65c846SMauro Carvalho Chehabtry_direct_io=x try direct transfer between user buffer and 344*bf65c846SMauro Carvalho Chehab tape drive if this is non-zero 345*bf65c846SMauro Carvalho Chehab========================== =========================================== 346*bf65c846SMauro Carvalho Chehab 347*bf65c846SMauro Carvalho ChehabNote that if the buffer size is changed but the write threshold is not 348*bf65c846SMauro Carvalho Chehabset, the write threshold is set to the new buffer size - 2 kB. 349*bf65c846SMauro Carvalho Chehab 350*bf65c846SMauro Carvalho Chehab 351*bf65c846SMauro Carvalho ChehabBoot Time Configuration 352*bf65c846SMauro Carvalho Chehab======================= 353*bf65c846SMauro Carvalho Chehab 354*bf65c846SMauro Carvalho ChehabIf the driver is compiled into the kernel, the same parameters can be 355*bf65c846SMauro Carvalho Chehabalso set using, e.g., the LILO command line. The preferred syntax is 356*bf65c846SMauro Carvalho Chehabto use the same keyword used when loading as module but prepended 357*bf65c846SMauro Carvalho Chehabwith 'st.'. For instance, to set the maximum number of scatter/gather 358*bf65c846SMauro Carvalho Chehabsegments, the parameter 'st.max_sg_segs=xx' should be used (xx is the 359*bf65c846SMauro Carvalho Chehabnumber of scatter/gather segments). 360*bf65c846SMauro Carvalho Chehab 361*bf65c846SMauro Carvalho ChehabFor compatibility, the old syntax from early 2.5 and 2.4 kernel 362*bf65c846SMauro Carvalho Chehabversions is supported. The same keywords can be used as when loading 363*bf65c846SMauro Carvalho Chehabthe driver as module. If several parameters are set, the keyword-value 364*bf65c846SMauro Carvalho Chehabpairs are separated with a comma (no spaces allowed). A colon can be 365*bf65c846SMauro Carvalho Chehabused instead of the equal mark. The definition is prepended by the 366*bf65c846SMauro Carvalho Chehabstring st=. Here is an example:: 367*bf65c846SMauro Carvalho Chehab 368*bf65c846SMauro Carvalho Chehab st=buffer_kbs:64,write_threshold_kbs:60 369*bf65c846SMauro Carvalho Chehab 370*bf65c846SMauro Carvalho ChehabThe following syntax used by the old kernel versions is also supported:: 371*bf65c846SMauro Carvalho Chehab 372*bf65c846SMauro Carvalho Chehab st=aa[,bb[,dd]] 373*bf65c846SMauro Carvalho Chehab 374*bf65c846SMauro Carvalho Chehabwhere: 375*bf65c846SMauro Carvalho Chehab 376*bf65c846SMauro Carvalho Chehab - aa is the buffer size for fixed block mode in 1024 byte units 377*bf65c846SMauro Carvalho Chehab - bb is the write threshold in 1024 byte units 378*bf65c846SMauro Carvalho Chehab - dd is the maximum number of scatter/gather segments 379*bf65c846SMauro Carvalho Chehab 380*bf65c846SMauro Carvalho Chehab 381*bf65c846SMauro Carvalho ChehabIOCTLs 382*bf65c846SMauro Carvalho Chehab====== 383*bf65c846SMauro Carvalho Chehab 384*bf65c846SMauro Carvalho ChehabThe tape is positioned and the drive parameters are set with ioctls 385*bf65c846SMauro Carvalho Chehabdefined in mtio.h The tape control program 'mt' uses these ioctls. Try 386*bf65c846SMauro Carvalho Chehabto find an mt that supports all of the Linux SCSI tape ioctls and 387*bf65c846SMauro Carvalho Chehabopens the device for writing if the tape contents will be modified 388*bf65c846SMauro Carvalho Chehab(look for a package mt-st* from the Linux ftp sites; the GNU mt does 389*bf65c846SMauro Carvalho Chehabnot open for writing for, e.g., erase). 390*bf65c846SMauro Carvalho Chehab 391*bf65c846SMauro Carvalho ChehabThe supported ioctls are: 392*bf65c846SMauro Carvalho Chehab 393*bf65c846SMauro Carvalho ChehabThe following use the structure mtop: 394*bf65c846SMauro Carvalho Chehab 395*bf65c846SMauro Carvalho ChehabMTFSF 396*bf65c846SMauro Carvalho Chehab Space forward over count filemarks. Tape positioned after filemark. 397*bf65c846SMauro Carvalho ChehabMTFSFM 398*bf65c846SMauro Carvalho Chehab As above but tape positioned before filemark. 399*bf65c846SMauro Carvalho ChehabMTBSF 400*bf65c846SMauro Carvalho Chehab Space backward over count filemarks. Tape positioned before 401*bf65c846SMauro Carvalho Chehab filemark. 402*bf65c846SMauro Carvalho ChehabMTBSFM 403*bf65c846SMauro Carvalho Chehab As above but ape positioned after filemark. 404*bf65c846SMauro Carvalho ChehabMTFSR 405*bf65c846SMauro Carvalho Chehab Space forward over count records. 406*bf65c846SMauro Carvalho ChehabMTBSR 407*bf65c846SMauro Carvalho Chehab Space backward over count records. 408*bf65c846SMauro Carvalho ChehabMTFSS 409*bf65c846SMauro Carvalho Chehab Space forward over count setmarks. 410*bf65c846SMauro Carvalho ChehabMTBSS 411*bf65c846SMauro Carvalho Chehab Space backward over count setmarks. 412*bf65c846SMauro Carvalho ChehabMTWEOF 413*bf65c846SMauro Carvalho Chehab Write count filemarks. 414*bf65c846SMauro Carvalho ChehabMTWEOFI 415*bf65c846SMauro Carvalho Chehab Write count filemarks with immediate bit set (i.e., does not 416*bf65c846SMauro Carvalho Chehab wait until data is on tape) 417*bf65c846SMauro Carvalho ChehabMTWSM 418*bf65c846SMauro Carvalho Chehab Write count setmarks. 419*bf65c846SMauro Carvalho ChehabMTREW 420*bf65c846SMauro Carvalho Chehab Rewind tape. 421*bf65c846SMauro Carvalho ChehabMTOFFL 422*bf65c846SMauro Carvalho Chehab Set device off line (often rewind plus eject). 423*bf65c846SMauro Carvalho ChehabMTNOP 424*bf65c846SMauro Carvalho Chehab Do nothing except flush the buffers. 425*bf65c846SMauro Carvalho ChehabMTRETEN 426*bf65c846SMauro Carvalho Chehab Re-tension tape. 427*bf65c846SMauro Carvalho ChehabMTEOM 428*bf65c846SMauro Carvalho Chehab Space to end of recorded data. 429*bf65c846SMauro Carvalho ChehabMTERASE 430*bf65c846SMauro Carvalho Chehab Erase tape. If the argument is zero, the short erase command 431*bf65c846SMauro Carvalho Chehab is used. The long erase command is used with all other values 432*bf65c846SMauro Carvalho Chehab of the argument. 433*bf65c846SMauro Carvalho ChehabMTSEEK 434*bf65c846SMauro Carvalho Chehab Seek to tape block count. Uses Tandberg-compatible seek (QFA) 435*bf65c846SMauro Carvalho Chehab for SCSI-1 drives and SCSI-2 seek for SCSI-2 drives. The file and 436*bf65c846SMauro Carvalho Chehab block numbers in the status are not valid after a seek. 437*bf65c846SMauro Carvalho ChehabMTSETBLK 438*bf65c846SMauro Carvalho Chehab Set the drive block size. Setting to zero sets the drive into 439*bf65c846SMauro Carvalho Chehab variable block mode (if applicable). 440*bf65c846SMauro Carvalho ChehabMTSETDENSITY 441*bf65c846SMauro Carvalho Chehab Sets the drive density code to arg. See drive 442*bf65c846SMauro Carvalho Chehab documentation for available codes. 443*bf65c846SMauro Carvalho ChehabMTLOCK and MTUNLOCK 444*bf65c846SMauro Carvalho Chehab Explicitly lock/unlock the tape drive door. 445*bf65c846SMauro Carvalho ChehabMTLOAD and MTUNLOAD 446*bf65c846SMauro Carvalho Chehab Explicitly load and unload the tape. If the 447*bf65c846SMauro Carvalho Chehab command argument x is between MT_ST_HPLOADER_OFFSET + 1 and 448*bf65c846SMauro Carvalho Chehab MT_ST_HPLOADER_OFFSET + 6, the number x is used sent to the 449*bf65c846SMauro Carvalho Chehab drive with the command and it selects the tape slot to use of 450*bf65c846SMauro Carvalho Chehab HP C1553A changer. 451*bf65c846SMauro Carvalho ChehabMTCOMPRESSION 452*bf65c846SMauro Carvalho Chehab Sets compressing or uncompressing drive mode using the 453*bf65c846SMauro Carvalho Chehab SCSI mode page 15. Note that some drives other methods for 454*bf65c846SMauro Carvalho Chehab control of compression. Some drives (like the Exabytes) use 455*bf65c846SMauro Carvalho Chehab density codes for compression control. Some drives use another 456*bf65c846SMauro Carvalho Chehab mode page but this page has not been implemented in the 457*bf65c846SMauro Carvalho Chehab driver. Some drives without compression capability will accept 458*bf65c846SMauro Carvalho Chehab any compression mode without error. 459*bf65c846SMauro Carvalho ChehabMTSETPART 460*bf65c846SMauro Carvalho Chehab Moves the tape to the partition given by the argument at the 461*bf65c846SMauro Carvalho Chehab next tape operation. The block at which the tape is positioned 462*bf65c846SMauro Carvalho Chehab is the block where the tape was previously positioned in the 463*bf65c846SMauro Carvalho Chehab new active partition unless the next tape operation is 464*bf65c846SMauro Carvalho Chehab MTSEEK. In this case the tape is moved directly to the block 465*bf65c846SMauro Carvalho Chehab specified by MTSEEK. MTSETPART is inactive unless 466*bf65c846SMauro Carvalho Chehab MT_ST_CAN_PARTITIONS set. 467*bf65c846SMauro Carvalho ChehabMTMKPART 468*bf65c846SMauro Carvalho Chehab Formats the tape with one partition (argument zero) or two 469*bf65c846SMauro Carvalho Chehab partitions (argument non-zero). If the argument is positive, 470*bf65c846SMauro Carvalho Chehab it specifies the size of partition 1 in megabytes. For DDS 471*bf65c846SMauro Carvalho Chehab drives and several early drives this is the physically first 472*bf65c846SMauro Carvalho Chehab partition of the tape. If the argument is negative, its absolute 473*bf65c846SMauro Carvalho Chehab value specifies the size of partition 0 in megabytes. This is 474*bf65c846SMauro Carvalho Chehab the physically first partition of many later drives, like the 475*bf65c846SMauro Carvalho Chehab LTO drives from LTO-5 upwards. The drive has to support partitions 476*bf65c846SMauro Carvalho Chehab with size specified by the initiator. Inactive unless 477*bf65c846SMauro Carvalho Chehab MT_ST_CAN_PARTITIONS set. 478*bf65c846SMauro Carvalho ChehabMTSETDRVBUFFER 479*bf65c846SMauro Carvalho Chehab Is used for several purposes. The command is obtained from count 480*bf65c846SMauro Carvalho Chehab with mask MT_SET_OPTIONS, the low order bits are used as argument. 481*bf65c846SMauro Carvalho Chehab This command is only allowed for the superuser (root). The 482*bf65c846SMauro Carvalho Chehab subcommands are: 483*bf65c846SMauro Carvalho Chehab 484*bf65c846SMauro Carvalho Chehab * 0 485*bf65c846SMauro Carvalho Chehab The drive buffer option is set to the argument. Zero means 486*bf65c846SMauro Carvalho Chehab no buffering. 487*bf65c846SMauro Carvalho Chehab * MT_ST_BOOLEANS 488*bf65c846SMauro Carvalho Chehab Sets the buffering options. The bits are the new states 489*bf65c846SMauro Carvalho Chehab (enabled/disabled) the following options (in the 490*bf65c846SMauro Carvalho Chehab parenthesis is specified whether the option is global or 491*bf65c846SMauro Carvalho Chehab can be specified differently for each mode): 492*bf65c846SMauro Carvalho Chehab 493*bf65c846SMauro Carvalho Chehab MT_ST_BUFFER_WRITES 494*bf65c846SMauro Carvalho Chehab write buffering (mode) 495*bf65c846SMauro Carvalho Chehab MT_ST_ASYNC_WRITES 496*bf65c846SMauro Carvalho Chehab asynchronous writes (mode) 497*bf65c846SMauro Carvalho Chehab MT_ST_READ_AHEAD 498*bf65c846SMauro Carvalho Chehab read ahead (mode) 499*bf65c846SMauro Carvalho Chehab MT_ST_TWO_FM 500*bf65c846SMauro Carvalho Chehab writing of two filemarks (global) 501*bf65c846SMauro Carvalho Chehab MT_ST_FAST_EOM 502*bf65c846SMauro Carvalho Chehab using the SCSI spacing to EOD (global) 503*bf65c846SMauro Carvalho Chehab MT_ST_AUTO_LOCK 504*bf65c846SMauro Carvalho Chehab automatic locking of the drive door (global) 505*bf65c846SMauro Carvalho Chehab MT_ST_DEF_WRITES 506*bf65c846SMauro Carvalho Chehab the defaults are meant only for writes (mode) 507*bf65c846SMauro Carvalho Chehab MT_ST_CAN_BSR 508*bf65c846SMauro Carvalho Chehab backspacing over more than one records can 509*bf65c846SMauro Carvalho Chehab be used for repositioning the tape (global) 510*bf65c846SMauro Carvalho Chehab MT_ST_NO_BLKLIMS 511*bf65c846SMauro Carvalho Chehab the driver does not ask the block limits 512*bf65c846SMauro Carvalho Chehab from the drive (block size can be changed only to 513*bf65c846SMauro Carvalho Chehab variable) (global) 514*bf65c846SMauro Carvalho Chehab MT_ST_CAN_PARTITIONS 515*bf65c846SMauro Carvalho Chehab enables support for partitioned 516*bf65c846SMauro Carvalho Chehab tapes (global) 517*bf65c846SMauro Carvalho Chehab MT_ST_SCSI2LOGICAL 518*bf65c846SMauro Carvalho Chehab the logical block number is used in 519*bf65c846SMauro Carvalho Chehab the MTSEEK and MTIOCPOS for SCSI-2 drives instead of 520*bf65c846SMauro Carvalho Chehab the device dependent address. It is recommended to set 521*bf65c846SMauro Carvalho Chehab this flag unless there are tapes using the device 522*bf65c846SMauro Carvalho Chehab dependent (from the old times) (global) 523*bf65c846SMauro Carvalho Chehab MT_ST_SYSV 524*bf65c846SMauro Carvalho Chehab sets the SYSV semantics (mode) 525*bf65c846SMauro Carvalho Chehab MT_ST_NOWAIT 526*bf65c846SMauro Carvalho Chehab enables immediate mode (i.e., don't wait for 527*bf65c846SMauro Carvalho Chehab the command to finish) for some commands (e.g., rewind) 528*bf65c846SMauro Carvalho Chehab MT_ST_NOWAIT_EOF 529*bf65c846SMauro Carvalho Chehab enables immediate filemark mode (i.e. when 530*bf65c846SMauro Carvalho Chehab writing a filemark, don't wait for it to complete). Please 531*bf65c846SMauro Carvalho Chehab see the BASICS note about MTWEOFI with respect to the 532*bf65c846SMauro Carvalho Chehab possible dangers of writing immediate filemarks. 533*bf65c846SMauro Carvalho Chehab MT_ST_SILI 534*bf65c846SMauro Carvalho Chehab enables setting the SILI bit in SCSI commands when 535*bf65c846SMauro Carvalho Chehab reading in variable block mode to enhance performance when 536*bf65c846SMauro Carvalho Chehab reading blocks shorter than the byte count; set this only 537*bf65c846SMauro Carvalho Chehab if you are sure that the drive supports SILI and the HBA 538*bf65c846SMauro Carvalho Chehab correctly returns transfer residuals 539*bf65c846SMauro Carvalho Chehab MT_ST_DEBUGGING 540*bf65c846SMauro Carvalho Chehab debugging (global; debugging must be 541*bf65c846SMauro Carvalho Chehab compiled into the driver) 542*bf65c846SMauro Carvalho Chehab 543*bf65c846SMauro Carvalho Chehab * MT_ST_SETBOOLEANS, MT_ST_CLEARBOOLEANS 544*bf65c846SMauro Carvalho Chehab Sets or clears the option bits. 545*bf65c846SMauro Carvalho Chehab * MT_ST_WRITE_THRESHOLD 546*bf65c846SMauro Carvalho Chehab Sets the write threshold for this device to kilobytes 547*bf65c846SMauro Carvalho Chehab specified by the lowest bits. 548*bf65c846SMauro Carvalho Chehab * MT_ST_DEF_BLKSIZE 549*bf65c846SMauro Carvalho Chehab Defines the default block size set automatically. Value 550*bf65c846SMauro Carvalho Chehab 0xffffff means that the default is not used any more. 551*bf65c846SMauro Carvalho Chehab * MT_ST_DEF_DENSITY, MT_ST_DEF_DRVBUFFER 552*bf65c846SMauro Carvalho Chehab Used to set or clear the density (8 bits), and drive buffer 553*bf65c846SMauro Carvalho Chehab state (3 bits). If the value is MT_ST_CLEAR_DEFAULT 554*bf65c846SMauro Carvalho Chehab (0xfffff) the default will not be used any more. Otherwise 555*bf65c846SMauro Carvalho Chehab the lowermost bits of the value contain the new value of 556*bf65c846SMauro Carvalho Chehab the parameter. 557*bf65c846SMauro Carvalho Chehab * MT_ST_DEF_COMPRESSION 558*bf65c846SMauro Carvalho Chehab The compression default will not be used if the value of 559*bf65c846SMauro Carvalho Chehab the lowermost byte is 0xff. Otherwise the lowermost bit 560*bf65c846SMauro Carvalho Chehab contains the new default. If the bits 8-15 are set to a 561*bf65c846SMauro Carvalho Chehab non-zero number, and this number is not 0xff, the number is 562*bf65c846SMauro Carvalho Chehab used as the compression algorithm. The value 563*bf65c846SMauro Carvalho Chehab MT_ST_CLEAR_DEFAULT can be used to clear the compression 564*bf65c846SMauro Carvalho Chehab default. 565*bf65c846SMauro Carvalho Chehab * MT_ST_SET_TIMEOUT 566*bf65c846SMauro Carvalho Chehab Set the normal timeout in seconds for this device. The 567*bf65c846SMauro Carvalho Chehab default is 900 seconds (15 minutes). The timeout should be 568*bf65c846SMauro Carvalho Chehab long enough for the retries done by the device while 569*bf65c846SMauro Carvalho Chehab reading/writing. 570*bf65c846SMauro Carvalho Chehab * MT_ST_SET_LONG_TIMEOUT 571*bf65c846SMauro Carvalho Chehab Set the long timeout that is used for operations that are 572*bf65c846SMauro Carvalho Chehab known to take a long time. The default is 14000 seconds 573*bf65c846SMauro Carvalho Chehab (3.9 hours). For erase this value is further multiplied by 574*bf65c846SMauro Carvalho Chehab eight. 575*bf65c846SMauro Carvalho Chehab * MT_ST_SET_CLN 576*bf65c846SMauro Carvalho Chehab Set the cleaning request interpretation parameters using 577*bf65c846SMauro Carvalho Chehab the lowest 24 bits of the argument. The driver can set the 578*bf65c846SMauro Carvalho Chehab generic status bit GMT_CLN if a cleaning request bit pattern 579*bf65c846SMauro Carvalho Chehab is found from the extended sense data. Many drives set one or 580*bf65c846SMauro Carvalho Chehab more bits in the extended sense data when the drive needs 581*bf65c846SMauro Carvalho Chehab cleaning. The bits are device-dependent. The driver is 582*bf65c846SMauro Carvalho Chehab given the number of the sense data byte (the lowest eight 583*bf65c846SMauro Carvalho Chehab bits of the argument; must be >= 18 (values 1 - 17 584*bf65c846SMauro Carvalho Chehab reserved) and <= the maximum requested sense data sixe), 585*bf65c846SMauro Carvalho Chehab a mask to select the relevant bits (the bits 9-16), and the 586*bf65c846SMauro Carvalho Chehab bit pattern (bits 17-23). If the bit pattern is zero, one 587*bf65c846SMauro Carvalho Chehab or more bits under the mask indicate cleaning request. If 588*bf65c846SMauro Carvalho Chehab the pattern is non-zero, the pattern must match the masked 589*bf65c846SMauro Carvalho Chehab sense data byte. 590*bf65c846SMauro Carvalho Chehab 591*bf65c846SMauro Carvalho Chehab (The cleaning bit is set if the additional sense code and 592*bf65c846SMauro Carvalho Chehab qualifier 00h 17h are seen regardless of the setting of 593*bf65c846SMauro Carvalho Chehab MT_ST_SET_CLN.) 594*bf65c846SMauro Carvalho Chehab 595*bf65c846SMauro Carvalho ChehabThe following ioctl uses the structure mtpos: 596*bf65c846SMauro Carvalho Chehab 597*bf65c846SMauro Carvalho ChehabMTIOCPOS 598*bf65c846SMauro Carvalho Chehab Reads the current position from the drive. Uses 599*bf65c846SMauro Carvalho Chehab Tandberg-compatible QFA for SCSI-1 drives and the SCSI-2 600*bf65c846SMauro Carvalho Chehab command for the SCSI-2 drives. 601*bf65c846SMauro Carvalho Chehab 602*bf65c846SMauro Carvalho ChehabThe following ioctl uses the structure mtget to return the status: 603*bf65c846SMauro Carvalho Chehab 604*bf65c846SMauro Carvalho ChehabMTIOCGET 605*bf65c846SMauro Carvalho Chehab Returns some status information. 606*bf65c846SMauro Carvalho Chehab The file number and block number within file are returned. The 607*bf65c846SMauro Carvalho Chehab block is -1 when it can't be determined (e.g., after MTBSF). 608*bf65c846SMauro Carvalho Chehab The drive type is either MTISSCSI1 or MTISSCSI2. 609*bf65c846SMauro Carvalho Chehab The number of recovered errors since the previous status call 610*bf65c846SMauro Carvalho Chehab is stored in the lower word of the field mt_erreg. 611*bf65c846SMauro Carvalho Chehab The current block size and the density code are stored in the field 612*bf65c846SMauro Carvalho Chehab mt_dsreg (shifts for the subfields are MT_ST_BLKSIZE_SHIFT and 613*bf65c846SMauro Carvalho Chehab MT_ST_DENSITY_SHIFT). 614*bf65c846SMauro Carvalho Chehab The GMT_xxx status bits reflect the drive status. GMT_DR_OPEN 615*bf65c846SMauro Carvalho Chehab is set if there is no tape in the drive. GMT_EOD means either 616*bf65c846SMauro Carvalho Chehab end of recorded data or end of tape. GMT_EOT means end of tape. 617*bf65c846SMauro Carvalho Chehab 618*bf65c846SMauro Carvalho Chehab 619*bf65c846SMauro Carvalho ChehabMiscellaneous Compile Options 620*bf65c846SMauro Carvalho Chehab============================= 621*bf65c846SMauro Carvalho Chehab 622*bf65c846SMauro Carvalho ChehabThe recovered write errors are considered fatal if ST_RECOVERED_WRITE_FATAL 623*bf65c846SMauro Carvalho Chehabis defined. 624*bf65c846SMauro Carvalho Chehab 625*bf65c846SMauro Carvalho ChehabThe maximum number of tape devices is determined by the define 626*bf65c846SMauro Carvalho ChehabST_MAX_TAPES. If more tapes are detected at driver initialization, the 627*bf65c846SMauro Carvalho Chehabmaximum is adjusted accordingly. 628*bf65c846SMauro Carvalho Chehab 629*bf65c846SMauro Carvalho ChehabImmediate return from tape positioning SCSI commands can be enabled by 630*bf65c846SMauro Carvalho Chehabdefining ST_NOWAIT. If this is defined, the user should take care that 631*bf65c846SMauro Carvalho Chehabthe next tape operation is not started before the previous one has 632*bf65c846SMauro Carvalho Chehabfinished. The drives and SCSI adapters should handle this condition 633*bf65c846SMauro Carvalho Chehabgracefully, but some drive/adapter combinations are known to hang the 634*bf65c846SMauro Carvalho ChehabSCSI bus in this case. 635*bf65c846SMauro Carvalho Chehab 636*bf65c846SMauro Carvalho ChehabThe MTEOM command is by default implemented as spacing over 32767 637*bf65c846SMauro Carvalho Chehabfilemarks. With this method the file number in the status is 638*bf65c846SMauro Carvalho Chehabcorrect. The user can request using direct spacing to EOD by setting 639*bf65c846SMauro Carvalho ChehabST_FAST_EOM 1 (or using the MT_ST_OPTIONS ioctl). In this case the file 640*bf65c846SMauro Carvalho Chehabnumber will be invalid. 641*bf65c846SMauro Carvalho Chehab 642*bf65c846SMauro Carvalho ChehabWhen using read ahead or buffered writes the position within the file 643*bf65c846SMauro Carvalho Chehabmay not be correct after the file is closed (correct position may 644*bf65c846SMauro Carvalho Chehabrequire backspacing over more than one record). The correct position 645*bf65c846SMauro Carvalho Chehabwithin file can be obtained if ST_IN_FILE_POS is defined at compile 646*bf65c846SMauro Carvalho Chehabtime or the MT_ST_CAN_BSR bit is set for the drive with an ioctl. 647*bf65c846SMauro Carvalho Chehab(The driver always backs over a filemark crossed by read ahead if the 648*bf65c846SMauro Carvalho Chehabuser does not request data that far.) 649*bf65c846SMauro Carvalho Chehab 650*bf65c846SMauro Carvalho Chehab 651*bf65c846SMauro Carvalho ChehabDebugging Hints 652*bf65c846SMauro Carvalho Chehab=============== 653*bf65c846SMauro Carvalho Chehab 654*bf65c846SMauro Carvalho ChehabDebugging code is now compiled in by default but debugging is turned off 655*bf65c846SMauro Carvalho Chehabwith the kernel module parameter debug_flag defaulting to 0. Debugging 656*bf65c846SMauro Carvalho Chehabcan still be switched on and off with an ioctl. To enable debug at 657*bf65c846SMauro Carvalho Chehabmodule load time add debug_flag=1 to the module load options, the 658*bf65c846SMauro Carvalho Chehabdebugging output is not voluminous. Debugging can also be enabled 659*bf65c846SMauro Carvalho Chehaband disabled by writing a '0' (disable) or '1' (enable) to the sysfs 660*bf65c846SMauro Carvalho Chehabfile /sys/bus/scsi/drivers/st/debug_flag. 661*bf65c846SMauro Carvalho Chehab 662*bf65c846SMauro Carvalho ChehabIf the tape seems to hang, I would be very interested to hear where 663*bf65c846SMauro Carvalho Chehabthe driver is waiting. With the command 'ps -l' you can see the state 664*bf65c846SMauro Carvalho Chehabof the process using the tape. If the state is D, the process is 665*bf65c846SMauro Carvalho Chehabwaiting for something. The field WCHAN tells where the driver is 666*bf65c846SMauro Carvalho Chehabwaiting. If you have the current System.map in the correct place (in 667*bf65c846SMauro Carvalho Chehab/boot for the procps I use) or have updated /etc/psdatabase (for kmem 668*bf65c846SMauro Carvalho Chehabps), ps writes the function name in the WCHAN field. If not, you have 669*bf65c846SMauro Carvalho Chehabto look up the function from System.map. 670*bf65c846SMauro Carvalho Chehab 671*bf65c846SMauro Carvalho ChehabNote also that the timeouts are very long compared to most other 672*bf65c846SMauro Carvalho Chehabdrivers. This means that the Linux driver may appear hung although the 673*bf65c846SMauro Carvalho Chehabreal reason is that the tape firmware has got confused. 674