Based on kernel version 4.1. Page generated on 2015-06-28 12:13 EST.
1 /* 2 * Ver 0.1 Nov 1 95 Pre-working code :-) 3 * Ver 0.2 Nov 23 95 A short backup (few megabytes) and restore procedure 4 * was successful ! (Using tar cvf ... on the block 5 * device interface). 6 * A longer backup resulted in major swapping, bad 7 * overall Linux performance and eventually failed as 8 * we received non serial read-ahead requests from the 9 * buffer cache. 10 * Ver 0.3 Nov 28 95 Long backups are now possible, thanks to the 11 * character device interface. Linux's responsiveness 12 * and performance doesn't seem to be much affected 13 * from the background backup procedure. 14 * Some general mtio.h magnetic tape operations are 15 * now supported by our character device. As a result, 16 * popular tape utilities are starting to work with 17 * ide tapes :-) 18 * The following configurations were tested: 19 * 1. An IDE ATAPI TAPE shares the same interface 20 * and irq with an IDE ATAPI CDROM. 21 * 2. An IDE ATAPI TAPE shares the same interface 22 * and irq with a normal IDE disk. 23 * Both configurations seemed to work just fine ! 24 * However, to be on the safe side, it is meanwhile 25 * recommended to give the IDE TAPE its own interface 26 * and irq. 27 * The one thing which needs to be done here is to 28 * add a "request postpone" feature to ide.c, 29 * so that we won't have to wait for the tape to finish 30 * performing a long media access (DSC) request (such 31 * as a rewind) before we can access the other device 32 * on the same interface. This effect doesn't disturb 33 * normal operation most of the time because read/write 34 * requests are relatively fast, and once we are 35 * performing one tape r/w request, a lot of requests 36 * from the other device can be queued and ide.c will 37 * service all of them after this single tape request. 38 * Ver 1.0 Dec 11 95 Integrated into Linux 1.3.46 development tree. 39 * On each read / write request, we now ask the drive 40 * if we can transfer a constant number of bytes 41 * (a parameter of the drive) only to its buffers, 42 * without causing actual media access. If we can't, 43 * we just wait until we can by polling the DSC bit. 44 * This ensures that while we are not transferring 45 * more bytes than the constant referred to above, the 46 * interrupt latency will not become too high and 47 * we won't cause an interrupt timeout, as happened 48 * occasionally in the previous version. 49 * While polling for DSC, the current request is 50 * postponed and ide.c is free to handle requests from 51 * the other device. This is handled transparently to 52 * ide.c. The hwgroup locking method which was used 53 * in the previous version was removed. 54 * Use of new general features which are provided by 55 * ide.c for use with atapi devices. 56 * (Programming done by Mark Lord) 57 * Few potential bug fixes (Again, suggested by Mark) 58 * Single character device data transfers are now 59 * not limited in size, as they were before. 60 * We are asking the tape about its recommended 61 * transfer unit and send a larger data transfer 62 * as several transfers of the above size. 63 * For best results, use an integral number of this 64 * basic unit (which is shown during driver 65 * initialization). I will soon add an ioctl to get 66 * this important parameter. 67 * Our data transfer buffer is allocated on startup, 68 * rather than before each data transfer. This should 69 * ensure that we will indeed have a data buffer. 70 * Ver 1.1 Dec 14 95 Fixed random problems which occurred when the tape 71 * shared an interface with another device. 72 * (poll_for_dsc was a complete mess). 73 * Removed some old (non-active) code which had 74 * to do with supporting buffer cache originated 75 * requests. 76 * The block device interface can now be opened, so 77 * that general ide driver features like the unmask 78 * interrupts flag can be selected with an ioctl. 79 * This is the only use of the block device interface. 80 * New fast pipelined operation mode (currently only on 81 * writes). When using the pipelined mode, the 82 * throughput can potentially reach the maximum 83 * tape supported throughput, regardless of the 84 * user backup program. On my tape drive, it sometimes 85 * boosted performance by a factor of 2. Pipelined 86 * mode is enabled by default, but since it has a few 87 * downfalls as well, you may want to disable it. 88 * A short explanation of the pipelined operation mode 89 * is available below. 90 * Ver 1.2 Jan 1 96 Eliminated pipelined mode race condition. 91 * Added pipeline read mode. As a result, restores 92 * are now as fast as backups. 93 * Optimized shared interface behavior. The new behavior 94 * typically results in better IDE bus efficiency and 95 * higher tape throughput. 96 * Pre-calculation of the expected read/write request 97 * service time, based on the tape's parameters. In 98 * the pipelined operation mode, this allows us to 99 * adjust our polling frequency to a much lower value, 100 * and thus to dramatically reduce our load on Linux, 101 * without any decrease in performance. 102 * Implemented additional mtio.h operations. 103 * The recommended user block size is returned by 104 * the MTIOCGET ioctl. 105 * Additional minor changes. 106 * Ver 1.3 Feb 9 96 Fixed pipelined read mode bug which prevented the 107 * use of some block sizes during a restore procedure. 108 * The character device interface will now present a 109 * continuous view of the media - any mix of block sizes 110 * during a backup/restore procedure is supported. The 111 * driver will buffer the requests internally and 112 * convert them to the tape's recommended transfer 113 * unit, making performance almost independent of the 114 * chosen user block size. 115 * Some improvements in error recovery. 116 * By cooperating with ide-dma.c, bus mastering DMA can 117 * now sometimes be used with IDE tape drives as well. 118 * Bus mastering DMA has the potential to dramatically 119 * reduce the CPU's overhead when accessing the device, 120 * and can be enabled by using hdparm -d1 on the tape's 121 * block device interface. For more info, read the 122 * comments in ide-dma.c. 123 * Ver 1.4 Mar 13 96 Fixed serialize support. 124 * Ver 1.5 Apr 12 96 Fixed shared interface operation, broken in 1.3.85. 125 * Fixed pipelined read mode inefficiency. 126 * Fixed nasty null dereferencing bug. 127 * Ver 1.6 Aug 16 96 Fixed FPU usage in the driver. 128 * Fixed end of media bug. 129 * Ver 1.7 Sep 10 96 Minor changes for the CONNER CTT8000-A model. 130 * Ver 1.8 Sep 26 96 Attempt to find a better balance between good 131 * interactive response and high system throughput. 132 * Ver 1.9 Nov 5 96 Automatically cross encountered filemarks rather 133 * than requiring an explicit FSF command. 134 * Abort pending requests at end of media. 135 * MTTELL was sometimes returning incorrect results. 136 * Return the real block size in the MTIOCGET ioctl. 137 * Some error recovery bug fixes. 138 * Ver 1.10 Nov 5 96 Major reorganization. 139 * Reduced CPU overhead a bit by eliminating internal 140 * bounce buffers. 141 * Added module support. 142 * Added multiple tape drives support. 143 * Added partition support. 144 * Rewrote DSC handling. 145 * Some portability fixes. 146 * Removed ide-tape.h. 147 * Additional minor changes. 148 * Ver 1.11 Dec 2 96 Bug fix in previous DSC timeout handling. 149 * Use ide_stall_queue() for DSC overlap. 150 * Use the maximum speed rather than the current speed 151 * to compute the request service time. 152 * Ver 1.12 Dec 7 97 Fix random memory overwriting and/or last block data 153 * corruption, which could occur if the total number 154 * of bytes written to the tape was not an integral 155 * number of tape blocks. 156 * Add support for INTERRUPT DRQ devices. 157 * Ver 1.13 Jan 2 98 Add "speed == 0" work-around for HP COLORADO 5GB 158 * Ver 1.14 Dec 30 98 Partial fixes for the Sony/AIWA tape drives. 159 * Replace cli()/sti() with hwgroup spinlocks. 160 * Ver 1.15 Mar 25 99 Fix SMP race condition by replacing hwgroup 161 * spinlock with private per-tape spinlock. 162 * Ver 1.16 Sep 1 99 Add OnStream tape support. 163 * Abort read pipeline on EOD. 164 * Wait for the tape to become ready in case it returns 165 * "in the process of becoming ready" on open(). 166 * Fix zero padding of the last written block in 167 * case the tape block size is larger than PAGE_SIZE. 168 * Decrease the default disconnection time to tn. 169 * Ver 1.16e Oct 3 99 Minor fixes. 170 * Ver 1.16e1 Oct 13 99 Patches by Arnold Niessen, 171 * email@example.com / firstname.lastname@example.org 172 * GO-1) Undefined code in idetape_read_position 173 * according to Gadi's email 174 * AJN-1) Minor fix asc == 11 should be asc == 0x11 175 * in idetape_issue_packet_command (did effect 176 * debugging output only) 177 * AJN-2) Added more debugging output, and 178 * added ide-tape: where missing. I would also 179 * like to add tape->name where possible 180 * AJN-3) Added different debug_level's 181 * via /proc/ide/hdc/settings 182 * "debug_level" determines amount of debugging output; 183 * can be changed using /proc/ide/hdx/settings 184 * 0 : almost no debugging output 185 * 1 : 0+output errors only 186 * 2 : 1+output all sensekey/asc 187 * 3 : 2+follow all chrdev related procedures 188 * 4 : 3+follow all procedures 189 * 5 : 4+include pc_stack rq_stack info 190 * 6 : 5+USE_COUNT updates 191 * AJN-4) Fixed timeout for retension in idetape_queue_pc_tail 192 * from 5 to 10 minutes 193 * AJN-5) Changed maximum number of blocks to skip when 194 * reading tapes with multiple consecutive write 195 * errors from 100 to 1000 in idetape_get_logical_blk 196 * Proposed changes to code: 197 * 1) output "logical_blk_num" via /proc 198 * 2) output "current_operation" via /proc 199 * 3) Either solve or document the fact that `mt rewind' is 200 * required after reading from /dev/nhtx to be 201 * able to rmmod the idetape module; 202 * Also, sometimes an application finishes but the 203 * device remains `busy' for some time. Same cause ? 204 * Proposed changes to release-notes: 205 * 4) write a simple `quickstart' section in the 206 * release notes; I volunteer if you don't want to 207 * 5) include a pointer to video4linux in the doc 208 * to stimulate video applications 209 * 6) release notes lines 331 and 362: explain what happens 210 * if the application data rate is higher than 1100 KB/s; 211 * similar approach to lower-than-500 kB/s ? 212 * 7) 6.6 Comparison; wouldn't it be better to allow different 213 * strategies for read and write ? 214 * Wouldn't it be better to control the tape buffer 215 * contents instead of the bandwidth ? 216 * 8) line 536: replace will by would (if I understand 217 * this section correctly, a hypothetical and unwanted situation 218 * is being described) 219 * Ver 1.16f Dec 15 99 Change place of the secondary OnStream header frames. 220 * Ver 1.17 Nov 2000 / Jan 2001 Marcel Mol, email@example.com 221 * - Add idetape_onstream_mode_sense_tape_parameter_page 222 * function to get tape capacity in frames: tape->capacity. 223 * - Add support for DI-50 drives( or any DI- drive). 224 * - 'workaround' for read error/blank block around block 3000. 225 * - Implement Early warning for end of media for Onstream. 226 * - Cosmetic code changes for readability. 227 * - Idetape_position_tape should not use SKIP bit during 228 * Onstream read recovery. 229 * - Add capacity, logical_blk_num and first/last_frame_position 230 * to /proc/ide/hd?/settings. 231 * - Module use count was gone in the Linux 2.4 driver. 232 * Ver 1.17a Apr 2001 Willem Riede firstname.lastname@example.org 233 * - Get drive's actual block size from mode sense block descriptor 234 * - Limit size of pipeline 235 * Ver 1.17b Oct 2002 Alan Stern <email@example.com> 236 * Changed IDETAPE_MIN_PIPELINE_STAGES to 1 and actually used 237 * it in the code! 238 * Actually removed aborted stages in idetape_abort_pipeline 239 * instead of just changing the command code. 240 * Made the transfer byte count for Request Sense equal to the 241 * actual length of the data transfer. 242 * Changed handling of partial data transfers: they do not 243 * cause DMA errors. 244 * Moved initiation of DMA transfers to the correct place. 245 * Removed reference to unallocated memory. 246 * Made __idetape_discard_read_pipeline return the number of 247 * sectors skipped, not the number of stages. 248 * Replaced errant kfree() calls with __idetape_kfree_stage(). 249 * Fixed off-by-one error in testing the pipeline length. 250 * Fixed handling of filemarks in the read pipeline. 251 * Small code optimization for MTBSF and MTBSFM ioctls. 252 * Don't try to unlock the door during device close if is 253 * already unlocked! 254 * Cosmetic fixes to miscellaneous debugging output messages. 255 * Set the minimum /proc/ide/hd?/settings values for "pipeline", 256 * "pipeline_min", and "pipeline_max" to 1. 257 */