ide-tape: move historical changelog to Documentation/ide/ChangeLog.ide-tape.1995-2002
Also, cleanup whitespace and update comments.
Bart:
- remove reference to drivers/block/ide.c
- move driver documentation to Documentation/ide/ide-tape.txt
Signed-off-by: Borislav Petkov <bbpetkov@yahoo.de>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
diff --git a/drivers/ide/ide-tape.c b/drivers/ide/ide-tape.c
index eff118b..045bd2a 100644
--- a/drivers/ide/ide-tape.c
+++ b/drivers/ide/ide-tape.c
@@ -1,424 +1,18 @@
/*
+ * IDE ATAPI streaming tape driver.
+ *
* Copyright (C) 1995-1999 Gadi Oxman <gadio@netvision.net.il>
* Copyright (C) 2003-2005 Bartlomiej Zolnierkiewicz
*
- * $Header$
- *
* This driver was constructed as a student project in the software laboratory
* of the faculty of electrical engineering in the Technion - Israel's
* Institute Of Technology, with the guide of Avner Lottem and Dr. Ilana David.
*
* It is hereby placed under the terms of the GNU general public license.
* (See linux/COPYING).
- */
-
-/*
- * IDE ATAPI streaming tape driver.
*
- * This driver is a part of the Linux ide driver and works in co-operation
- * with linux/drivers/block/ide.c.
- *
- * The driver, in co-operation with ide.c, basically traverses the
- * request-list for the block device interface. The character device
- * interface, on the other hand, creates new requests, adds them
- * to the request-list of the block device, and waits for their completion.
- *
- * Pipelined operation mode is now supported on both reads and writes.
- *
- * The block device major and minor numbers are determined from the
- * tape's relative position in the ide interfaces, as explained in ide.c.
- *
- * The character device interface consists of the following devices:
- *
- * ht0 major 37, minor 0 first IDE tape, rewind on close.
- * ht1 major 37, minor 1 second IDE tape, rewind on close.
- * ...
- * nht0 major 37, minor 128 first IDE tape, no rewind on close.
- * nht1 major 37, minor 129 second IDE tape, no rewind on close.
- * ...
- *
- * Run linux/scripts/MAKEDEV.ide to create the above entries.
- *
- * The general magnetic tape commands compatible interface, as defined by
- * include/linux/mtio.h, is accessible through the character device.
- *
- * General ide driver configuration options, such as the interrupt-unmask
- * flag, can be configured by issuing an ioctl to the block device interface,
- * as any other ide device.
- *
- * Our own ide-tape ioctl's can be issued to either the block device or
- * the character device interface.
- *
- * Maximal throughput with minimal bus load will usually be achieved in the
- * following scenario:
- *
- * 1. ide-tape is operating in the pipelined operation mode.
- * 2. No buffering is performed by the user backup program.
- *
- * Testing was done with a 2 GB CONNER CTMA 4000 IDE ATAPI Streaming Tape Drive.
- *
- * Ver 0.1 Nov 1 95 Pre-working code :-)
- * Ver 0.2 Nov 23 95 A short backup (few megabytes) and restore procedure
- * was successful ! (Using tar cvf ... on the block
- * device interface).
- * A longer backup resulted in major swapping, bad
- * overall Linux performance and eventually failed as
- * we received non serial read-ahead requests from the
- * buffer cache.
- * Ver 0.3 Nov 28 95 Long backups are now possible, thanks to the
- * character device interface. Linux's responsiveness
- * and performance doesn't seem to be much affected
- * from the background backup procedure.
- * Some general mtio.h magnetic tape operations are
- * now supported by our character device. As a result,
- * popular tape utilities are starting to work with
- * ide tapes :-)
- * The following configurations were tested:
- * 1. An IDE ATAPI TAPE shares the same interface
- * and irq with an IDE ATAPI CDROM.
- * 2. An IDE ATAPI TAPE shares the same interface
- * and irq with a normal IDE disk.
- * Both configurations seemed to work just fine !
- * However, to be on the safe side, it is meanwhile
- * recommended to give the IDE TAPE its own interface
- * and irq.
- * The one thing which needs to be done here is to
- * add a "request postpone" feature to ide.c,
- * so that we won't have to wait for the tape to finish
- * performing a long media access (DSC) request (such
- * as a rewind) before we can access the other device
- * on the same interface. This effect doesn't disturb
- * normal operation most of the time because read/write
- * requests are relatively fast, and once we are
- * performing one tape r/w request, a lot of requests
- * from the other device can be queued and ide.c will
- * service all of them after this single tape request.
- * Ver 1.0 Dec 11 95 Integrated into Linux 1.3.46 development tree.
- * On each read / write request, we now ask the drive
- * if we can transfer a constant number of bytes
- * (a parameter of the drive) only to its buffers,
- * without causing actual media access. If we can't,
- * we just wait until we can by polling the DSC bit.
- * This ensures that while we are not transferring
- * more bytes than the constant referred to above, the
- * interrupt latency will not become too high and
- * we won't cause an interrupt timeout, as happened
- * occasionally in the previous version.
- * While polling for DSC, the current request is
- * postponed and ide.c is free to handle requests from
- * the other device. This is handled transparently to
- * ide.c. The hwgroup locking method which was used
- * in the previous version was removed.
- * Use of new general features which are provided by
- * ide.c for use with atapi devices.
- * (Programming done by Mark Lord)
- * Few potential bug fixes (Again, suggested by Mark)
- * Single character device data transfers are now
- * not limited in size, as they were before.
- * We are asking the tape about its recommended
- * transfer unit and send a larger data transfer
- * as several transfers of the above size.
- * For best results, use an integral number of this
- * basic unit (which is shown during driver
- * initialization). I will soon add an ioctl to get
- * this important parameter.
- * Our data transfer buffer is allocated on startup,
- * rather than before each data transfer. This should
- * ensure that we will indeed have a data buffer.
- * Ver 1.1 Dec 14 95 Fixed random problems which occurred when the tape
- * shared an interface with another device.
- * (poll_for_dsc was a complete mess).
- * Removed some old (non-active) code which had
- * to do with supporting buffer cache originated
- * requests.
- * The block device interface can now be opened, so
- * that general ide driver features like the unmask
- * interrupts flag can be selected with an ioctl.
- * This is the only use of the block device interface.
- * New fast pipelined operation mode (currently only on
- * writes). When using the pipelined mode, the
- * throughput can potentially reach the maximum
- * tape supported throughput, regardless of the
- * user backup program. On my tape drive, it sometimes
- * boosted performance by a factor of 2. Pipelined
- * mode is enabled by default, but since it has a few
- * downfalls as well, you may want to disable it.
- * A short explanation of the pipelined operation mode
- * is available below.
- * Ver 1.2 Jan 1 96 Eliminated pipelined mode race condition.
- * Added pipeline read mode. As a result, restores
- * are now as fast as backups.
- * Optimized shared interface behavior. The new behavior
- * typically results in better IDE bus efficiency and
- * higher tape throughput.
- * Pre-calculation of the expected read/write request
- * service time, based on the tape's parameters. In
- * the pipelined operation mode, this allows us to
- * adjust our polling frequency to a much lower value,
- * and thus to dramatically reduce our load on Linux,
- * without any decrease in performance.
- * Implemented additional mtio.h operations.
- * The recommended user block size is returned by
- * the MTIOCGET ioctl.
- * Additional minor changes.
- * Ver 1.3 Feb 9 96 Fixed pipelined read mode bug which prevented the
- * use of some block sizes during a restore procedure.
- * The character device interface will now present a
- * continuous view of the media - any mix of block sizes
- * during a backup/restore procedure is supported. The
- * driver will buffer the requests internally and
- * convert them to the tape's recommended transfer
- * unit, making performance almost independent of the
- * chosen user block size.
- * Some improvements in error recovery.
- * By cooperating with ide-dma.c, bus mastering DMA can
- * now sometimes be used with IDE tape drives as well.
- * Bus mastering DMA has the potential to dramatically
- * reduce the CPU's overhead when accessing the device,
- * and can be enabled by using hdparm -d1 on the tape's
- * block device interface. For more info, read the
- * comments in ide-dma.c.
- * Ver 1.4 Mar 13 96 Fixed serialize support.
- * Ver 1.5 Apr 12 96 Fixed shared interface operation, broken in 1.3.85.
- * Fixed pipelined read mode inefficiency.
- * Fixed nasty null dereferencing bug.
- * Ver 1.6 Aug 16 96 Fixed FPU usage in the driver.
- * Fixed end of media bug.
- * Ver 1.7 Sep 10 96 Minor changes for the CONNER CTT8000-A model.
- * Ver 1.8 Sep 26 96 Attempt to find a better balance between good
- * interactive response and high system throughput.
- * Ver 1.9 Nov 5 96 Automatically cross encountered filemarks rather
- * than requiring an explicit FSF command.
- * Abort pending requests at end of media.
- * MTTELL was sometimes returning incorrect results.
- * Return the real block size in the MTIOCGET ioctl.
- * Some error recovery bug fixes.
- * Ver 1.10 Nov 5 96 Major reorganization.
- * Reduced CPU overhead a bit by eliminating internal
- * bounce buffers.
- * Added module support.
- * Added multiple tape drives support.
- * Added partition support.
- * Rewrote DSC handling.
- * Some portability fixes.
- * Removed ide-tape.h.
- * Additional minor changes.
- * Ver 1.11 Dec 2 96 Bug fix in previous DSC timeout handling.
- * Use ide_stall_queue() for DSC overlap.
- * Use the maximum speed rather than the current speed
- * to compute the request service time.
- * Ver 1.12 Dec 7 97 Fix random memory overwriting and/or last block data
- * corruption, which could occur if the total number
- * of bytes written to the tape was not an integral
- * number of tape blocks.
- * Add support for INTERRUPT DRQ devices.
- * Ver 1.13 Jan 2 98 Add "speed == 0" work-around for HP COLORADO 5GB
- * Ver 1.14 Dec 30 98 Partial fixes for the Sony/AIWA tape drives.
- * Replace cli()/sti() with hwgroup spinlocks.
- * Ver 1.15 Mar 25 99 Fix SMP race condition by replacing hwgroup
- * spinlock with private per-tape spinlock.
- * Ver 1.16 Sep 1 99 Add OnStream tape support.
- * Abort read pipeline on EOD.
- * Wait for the tape to become ready in case it returns
- * "in the process of becoming ready" on open().
- * Fix zero padding of the last written block in
- * case the tape block size is larger than PAGE_SIZE.
- * Decrease the default disconnection time to tn.
- * Ver 1.16e Oct 3 99 Minor fixes.
- * Ver 1.16e1 Oct 13 99 Patches by Arnold Niessen,
- * niessen@iae.nl / arnold.niessen@philips.com
- * GO-1) Undefined code in idetape_read_position
- * according to Gadi's email
- * AJN-1) Minor fix asc == 11 should be asc == 0x11
- * in idetape_issue_packet_command (did effect
- * debugging output only)
- * AJN-2) Added more debugging output, and
- * added ide-tape: where missing. I would also
- * like to add tape->name where possible
- * AJN-3) Added different debug_level's
- * via /proc/ide/hdc/settings
- * "debug_level" determines amount of debugging output;
- * can be changed using /proc/ide/hdx/settings
- * 0 : almost no debugging output
- * 1 : 0+output errors only
- * 2 : 1+output all sensekey/asc
- * 3 : 2+follow all chrdev related procedures
- * 4 : 3+follow all procedures
- * 5 : 4+include pc_stack rq_stack info
- * 6 : 5+USE_COUNT updates
- * AJN-4) Fixed timeout for retension in idetape_queue_pc_tail
- * from 5 to 10 minutes
- * AJN-5) Changed maximum number of blocks to skip when
- * reading tapes with multiple consecutive write
- * errors from 100 to 1000 in idetape_get_logical_blk
- * Proposed changes to code:
- * 1) output "logical_blk_num" via /proc
- * 2) output "current_operation" via /proc
- * 3) Either solve or document the fact that `mt rewind' is
- * required after reading from /dev/nhtx to be
- * able to rmmod the idetape module;
- * Also, sometimes an application finishes but the
- * device remains `busy' for some time. Same cause ?
- * Proposed changes to release-notes:
- * 4) write a simple `quickstart' section in the
- * release notes; I volunteer if you don't want to
- * 5) include a pointer to video4linux in the doc
- * to stimulate video applications
- * 6) release notes lines 331 and 362: explain what happens
- * if the application data rate is higher than 1100 KB/s;
- * similar approach to lower-than-500 kB/s ?
- * 7) 6.6 Comparison; wouldn't it be better to allow different
- * strategies for read and write ?
- * Wouldn't it be better to control the tape buffer
- * contents instead of the bandwidth ?
- * 8) line 536: replace will by would (if I understand
- * this section correctly, a hypothetical and unwanted situation
- * is being described)
- * Ver 1.16f Dec 15 99 Change place of the secondary OnStream header frames.
- * Ver 1.17 Nov 2000 / Jan 2001 Marcel Mol, marcel@mesa.nl
- * - Add idetape_onstream_mode_sense_tape_parameter_page
- * function to get tape capacity in frames: tape->capacity.
- * - Add support for DI-50 drives( or any DI- drive).
- * - 'workaround' for read error/blank block around block 3000.
- * - Implement Early warning for end of media for Onstream.
- * - Cosmetic code changes for readability.
- * - Idetape_position_tape should not use SKIP bit during
- * Onstream read recovery.
- * - Add capacity, logical_blk_num and first/last_frame_position
- * to /proc/ide/hd?/settings.
- * - Module use count was gone in the Linux 2.4 driver.
- * Ver 1.17a Apr 2001 Willem Riede osst@riede.org
- * - Get drive's actual block size from mode sense block descriptor
- * - Limit size of pipeline
- * Ver 1.17b Oct 2002 Alan Stern <stern@rowland.harvard.edu>
- * Changed IDETAPE_MIN_PIPELINE_STAGES to 1 and actually used
- * it in the code!
- * Actually removed aborted stages in idetape_abort_pipeline
- * instead of just changing the command code.
- * Made the transfer byte count for Request Sense equal to the
- * actual length of the data transfer.
- * Changed handling of partial data transfers: they do not
- * cause DMA errors.
- * Moved initiation of DMA transfers to the correct place.
- * Removed reference to unallocated memory.
- * Made __idetape_discard_read_pipeline return the number of
- * sectors skipped, not the number of stages.
- * Replaced errant kfree() calls with __idetape_kfree_stage().
- * Fixed off-by-one error in testing the pipeline length.
- * Fixed handling of filemarks in the read pipeline.
- * Small code optimization for MTBSF and MTBSFM ioctls.
- * Don't try to unlock the door during device close if is
- * already unlocked!
- * Cosmetic fixes to miscellaneous debugging output messages.
- * Set the minimum /proc/ide/hd?/settings values for "pipeline",
- * "pipeline_min", and "pipeline_max" to 1.
- *
- * Here are some words from the first releases of hd.c, which are quoted
- * in ide.c and apply here as well:
- *
- * | Special care is recommended. Have Fun!
- *
- */
-
-/*
- * An overview of the pipelined operation mode.
- *
- * In the pipelined write mode, we will usually just add requests to our
- * pipeline and return immediately, before we even start to service them. The
- * user program will then have enough time to prepare the next request while
- * we are still busy servicing previous requests. In the pipelined read mode,
- * the situation is similar - we add read-ahead requests into the pipeline,
- * before the user even requested them.
- *
- * The pipeline can be viewed as a "safety net" which will be activated when
- * the system load is high and prevents the user backup program from keeping up
- * with the current tape speed. At this point, the pipeline will get
- * shorter and shorter but the tape will still be streaming at the same speed.
- * Assuming we have enough pipeline stages, the system load will hopefully
- * decrease before the pipeline is completely empty, and the backup program
- * will be able to "catch up" and refill the pipeline again.
- *
- * When using the pipelined mode, it would be best to disable any type of
- * buffering done by the user program, as ide-tape already provides all the
- * benefits in the kernel, where it can be done in a more efficient way.
- * As we will usually not block the user program on a request, the most
- * efficient user code will then be a simple read-write-read-... cycle.
- * Any additional logic will usually just slow down the backup process.
- *
- * Using the pipelined mode, I get a constant over 400 KBps throughput,
- * which seems to be the maximum throughput supported by my tape.
- *
- * However, there are some downfalls:
- *
- * 1. We use memory (for data buffers) in proportional to the number
- * of pipeline stages (each stage is about 26 KB with my tape).
- * 2. In the pipelined write mode, we cheat and postpone error codes
- * to the user task. In read mode, the actual tape position
- * will be a bit further than the last requested block.
- *
- * Concerning (1):
- *
- * 1. We allocate stages dynamically only when we need them. When
- * we don't need them, we don't consume additional memory. In
- * case we can't allocate stages, we just manage without them
- * (at the expense of decreased throughput) so when Linux is
- * tight in memory, we will not pose additional difficulties.
- *
- * 2. The maximum number of stages (which is, in fact, the maximum
- * amount of memory) which we allocate is limited by the compile
- * time parameter IDETAPE_MAX_PIPELINE_STAGES.
- *
- * 3. The maximum number of stages is a controlled parameter - We
- * don't start from the user defined maximum number of stages
- * but from the lower IDETAPE_MIN_PIPELINE_STAGES (again, we
- * will not even allocate this amount of stages if the user
- * program can't handle the speed). We then implement a feedback
- * loop which checks if the pipeline is empty, and if it is, we
- * increase the maximum number of stages as necessary until we
- * reach the optimum value which just manages to keep the tape
- * busy with minimum allocated memory or until we reach
- * IDETAPE_MAX_PIPELINE_STAGES.
- *
- * Concerning (2):
- *
- * In pipelined write mode, ide-tape can not return accurate error codes
- * to the user program since we usually just add the request to the
- * pipeline without waiting for it to be serviced. In case an error
- * occurs, I will report it on the next user request.
- *
- * In the pipelined read mode, subsequent read requests or forward
- * filemark spacing will perform correctly, as we preserve all blocks
- * and filemarks which we encountered during our excess read-ahead.
- *
- * For accurate tape positioning and error reporting, disabling
- * pipelined mode might be the best option.
- *
- * You can enable/disable/tune the pipelined operation mode by adjusting
- * the compile time parameters below.
- */
-
-/*
- * Possible improvements.
- *
- * 1. Support for the ATAPI overlap protocol.
- *
- * In order to maximize bus throughput, we currently use the DSC
- * overlap method which enables ide.c to service requests from the
- * other device while the tape is busy executing a command. The
- * DSC overlap method involves polling the tape's status register
- * for the DSC bit, and servicing the other device while the tape
- * isn't ready.
- *
- * In the current QIC development standard (December 1995),
- * it is recommended that new tape drives will *in addition*
- * implement the ATAPI overlap protocol, which is used for the
- * same purpose - efficient use of the IDE bus, but is interrupt
- * driven and thus has much less CPU overhead.
- *
- * ATAPI overlap is likely to be supported in most new ATAPI
- * devices, including new ATAPI cdroms, and thus provides us
- * a method by which we can achieve higher throughput when
- * sharing a (fast) ATA-2 disk with any (slow) new ATAPI device.
+ * For a historical changelog see
+ * Documentation/ide/ChangeLog.ide-tape.1995-2002
*/
#define IDETAPE_VERSION "1.19"