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>hifive-unleashed-5.1
Borislav Petkov
Bartlomiej Zolnierkiewicz
parent
dcb425f557
commit
5ce78af4be
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@ -0,0 +1,257 @@
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/*
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* Ver 0.1 Nov 1 95 Pre-working code :-)
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* Ver 0.2 Nov 23 95 A short backup (few megabytes) and restore procedure
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* was successful ! (Using tar cvf ... on the block
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* device interface).
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* A longer backup resulted in major swapping, bad
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* overall Linux performance and eventually failed as
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* we received non serial read-ahead requests from the
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* buffer cache.
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* Ver 0.3 Nov 28 95 Long backups are now possible, thanks to the
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* character device interface. Linux's responsiveness
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* and performance doesn't seem to be much affected
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* from the background backup procedure.
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* Some general mtio.h magnetic tape operations are
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* now supported by our character device. As a result,
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* popular tape utilities are starting to work with
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* ide tapes :-)
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* The following configurations were tested:
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* 1. An IDE ATAPI TAPE shares the same interface
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* and irq with an IDE ATAPI CDROM.
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* 2. An IDE ATAPI TAPE shares the same interface
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* and irq with a normal IDE disk.
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* Both configurations seemed to work just fine !
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* However, to be on the safe side, it is meanwhile
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* recommended to give the IDE TAPE its own interface
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* and irq.
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* The one thing which needs to be done here is to
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* add a "request postpone" feature to ide.c,
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* so that we won't have to wait for the tape to finish
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* performing a long media access (DSC) request (such
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* as a rewind) before we can access the other device
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* on the same interface. This effect doesn't disturb
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* normal operation most of the time because read/write
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* requests are relatively fast, and once we are
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* performing one tape r/w request, a lot of requests
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* from the other device can be queued and ide.c will
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* service all of them after this single tape request.
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* Ver 1.0 Dec 11 95 Integrated into Linux 1.3.46 development tree.
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* On each read / write request, we now ask the drive
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* if we can transfer a constant number of bytes
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* (a parameter of the drive) only to its buffers,
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* without causing actual media access. If we can't,
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* we just wait until we can by polling the DSC bit.
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* This ensures that while we are not transferring
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* more bytes than the constant referred to above, the
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* interrupt latency will not become too high and
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* we won't cause an interrupt timeout, as happened
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* occasionally in the previous version.
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* While polling for DSC, the current request is
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* postponed and ide.c is free to handle requests from
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* the other device. This is handled transparently to
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* ide.c. The hwgroup locking method which was used
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* in the previous version was removed.
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* Use of new general features which are provided by
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* ide.c for use with atapi devices.
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* (Programming done by Mark Lord)
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* Few potential bug fixes (Again, suggested by Mark)
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* Single character device data transfers are now
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* not limited in size, as they were before.
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* We are asking the tape about its recommended
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* transfer unit and send a larger data transfer
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* as several transfers of the above size.
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* For best results, use an integral number of this
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* basic unit (which is shown during driver
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* initialization). I will soon add an ioctl to get
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* this important parameter.
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* Our data transfer buffer is allocated on startup,
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* rather than before each data transfer. This should
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* ensure that we will indeed have a data buffer.
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* Ver 1.1 Dec 14 95 Fixed random problems which occurred when the tape
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* shared an interface with another device.
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* (poll_for_dsc was a complete mess).
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* Removed some old (non-active) code which had
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* to do with supporting buffer cache originated
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* requests.
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* The block device interface can now be opened, so
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* that general ide driver features like the unmask
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* interrupts flag can be selected with an ioctl.
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* This is the only use of the block device interface.
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* New fast pipelined operation mode (currently only on
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* writes). When using the pipelined mode, the
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* throughput can potentially reach the maximum
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* tape supported throughput, regardless of the
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* user backup program. On my tape drive, it sometimes
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* boosted performance by a factor of 2. Pipelined
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* mode is enabled by default, but since it has a few
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* downfalls as well, you may want to disable it.
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* A short explanation of the pipelined operation mode
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* is available below.
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* Ver 1.2 Jan 1 96 Eliminated pipelined mode race condition.
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* Added pipeline read mode. As a result, restores
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* are now as fast as backups.
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* Optimized shared interface behavior. The new behavior
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* typically results in better IDE bus efficiency and
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* higher tape throughput.
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* Pre-calculation of the expected read/write request
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* service time, based on the tape's parameters. In
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* the pipelined operation mode, this allows us to
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* adjust our polling frequency to a much lower value,
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* and thus to dramatically reduce our load on Linux,
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* without any decrease in performance.
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* Implemented additional mtio.h operations.
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* The recommended user block size is returned by
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* the MTIOCGET ioctl.
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* Additional minor changes.
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* Ver 1.3 Feb 9 96 Fixed pipelined read mode bug which prevented the
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* use of some block sizes during a restore procedure.
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* The character device interface will now present a
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* continuous view of the media - any mix of block sizes
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* during a backup/restore procedure is supported. The
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* driver will buffer the requests internally and
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* convert them to the tape's recommended transfer
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* unit, making performance almost independent of the
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* chosen user block size.
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* Some improvements in error recovery.
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* By cooperating with ide-dma.c, bus mastering DMA can
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* now sometimes be used with IDE tape drives as well.
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* Bus mastering DMA has the potential to dramatically
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* reduce the CPU's overhead when accessing the device,
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* and can be enabled by using hdparm -d1 on the tape's
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* block device interface. For more info, read the
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* comments in ide-dma.c.
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* Ver 1.4 Mar 13 96 Fixed serialize support.
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* Ver 1.5 Apr 12 96 Fixed shared interface operation, broken in 1.3.85.
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* Fixed pipelined read mode inefficiency.
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* Fixed nasty null dereferencing bug.
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* Ver 1.6 Aug 16 96 Fixed FPU usage in the driver.
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* Fixed end of media bug.
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* Ver 1.7 Sep 10 96 Minor changes for the CONNER CTT8000-A model.
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* Ver 1.8 Sep 26 96 Attempt to find a better balance between good
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* interactive response and high system throughput.
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* Ver 1.9 Nov 5 96 Automatically cross encountered filemarks rather
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* than requiring an explicit FSF command.
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* Abort pending requests at end of media.
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* MTTELL was sometimes returning incorrect results.
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* Return the real block size in the MTIOCGET ioctl.
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* Some error recovery bug fixes.
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* Ver 1.10 Nov 5 96 Major reorganization.
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* Reduced CPU overhead a bit by eliminating internal
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* bounce buffers.
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* Added module support.
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* Added multiple tape drives support.
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* Added partition support.
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* Rewrote DSC handling.
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* Some portability fixes.
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* Removed ide-tape.h.
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* Additional minor changes.
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* Ver 1.11 Dec 2 96 Bug fix in previous DSC timeout handling.
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* Use ide_stall_queue() for DSC overlap.
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* Use the maximum speed rather than the current speed
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* to compute the request service time.
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* Ver 1.12 Dec 7 97 Fix random memory overwriting and/or last block data
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* corruption, which could occur if the total number
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* of bytes written to the tape was not an integral
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* number of tape blocks.
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* Add support for INTERRUPT DRQ devices.
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* Ver 1.13 Jan 2 98 Add "speed == 0" work-around for HP COLORADO 5GB
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* Ver 1.14 Dec 30 98 Partial fixes for the Sony/AIWA tape drives.
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* Replace cli()/sti() with hwgroup spinlocks.
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* Ver 1.15 Mar 25 99 Fix SMP race condition by replacing hwgroup
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* spinlock with private per-tape spinlock.
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* Ver 1.16 Sep 1 99 Add OnStream tape support.
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* Abort read pipeline on EOD.
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* Wait for the tape to become ready in case it returns
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* "in the process of becoming ready" on open().
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* Fix zero padding of the last written block in
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* case the tape block size is larger than PAGE_SIZE.
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* Decrease the default disconnection time to tn.
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* Ver 1.16e Oct 3 99 Minor fixes.
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* Ver 1.16e1 Oct 13 99 Patches by Arnold Niessen,
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* niessen@iae.nl / arnold.niessen@philips.com
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* GO-1) Undefined code in idetape_read_position
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* according to Gadi's email
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* AJN-1) Minor fix asc == 11 should be asc == 0x11
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* in idetape_issue_packet_command (did effect
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* debugging output only)
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* AJN-2) Added more debugging output, and
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* added ide-tape: where missing. I would also
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* like to add tape->name where possible
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* AJN-3) Added different debug_level's
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* via /proc/ide/hdc/settings
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* "debug_level" determines amount of debugging output;
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* can be changed using /proc/ide/hdx/settings
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* 0 : almost no debugging output
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* 1 : 0+output errors only
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* 2 : 1+output all sensekey/asc
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* 3 : 2+follow all chrdev related procedures
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* 4 : 3+follow all procedures
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* 5 : 4+include pc_stack rq_stack info
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* 6 : 5+USE_COUNT updates
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* AJN-4) Fixed timeout for retension in idetape_queue_pc_tail
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* from 5 to 10 minutes
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* AJN-5) Changed maximum number of blocks to skip when
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* reading tapes with multiple consecutive write
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* errors from 100 to 1000 in idetape_get_logical_blk
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* Proposed changes to code:
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* 1) output "logical_blk_num" via /proc
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* 2) output "current_operation" via /proc
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* 3) Either solve or document the fact that `mt rewind' is
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* required after reading from /dev/nhtx to be
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* able to rmmod the idetape module;
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* Also, sometimes an application finishes but the
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* device remains `busy' for some time. Same cause ?
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* Proposed changes to release-notes:
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* 4) write a simple `quickstart' section in the
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* release notes; I volunteer if you don't want to
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* 5) include a pointer to video4linux in the doc
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* to stimulate video applications
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* 6) release notes lines 331 and 362: explain what happens
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* if the application data rate is higher than 1100 KB/s;
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* similar approach to lower-than-500 kB/s ?
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* 7) 6.6 Comparison; wouldn't it be better to allow different
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* strategies for read and write ?
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* Wouldn't it be better to control the tape buffer
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* contents instead of the bandwidth ?
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* 8) line 536: replace will by would (if I understand
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* this section correctly, a hypothetical and unwanted situation
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* is being described)
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* Ver 1.16f Dec 15 99 Change place of the secondary OnStream header frames.
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* Ver 1.17 Nov 2000 / Jan 2001 Marcel Mol, marcel@mesa.nl
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* - Add idetape_onstream_mode_sense_tape_parameter_page
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* function to get tape capacity in frames: tape->capacity.
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* - Add support for DI-50 drives( or any DI- drive).
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* - 'workaround' for read error/blank block around block 3000.
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* - Implement Early warning for end of media for Onstream.
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* - Cosmetic code changes for readability.
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* - Idetape_position_tape should not use SKIP bit during
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* Onstream read recovery.
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* - Add capacity, logical_blk_num and first/last_frame_position
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* to /proc/ide/hd?/settings.
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* - Module use count was gone in the Linux 2.4 driver.
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* Ver 1.17a Apr 2001 Willem Riede osst@riede.org
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* - Get drive's actual block size from mode sense block descriptor
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* - Limit size of pipeline
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* Ver 1.17b Oct 2002 Alan Stern <stern@rowland.harvard.edu>
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* Changed IDETAPE_MIN_PIPELINE_STAGES to 1 and actually used
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* it in the code!
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* Actually removed aborted stages in idetape_abort_pipeline
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* instead of just changing the command code.
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* Made the transfer byte count for Request Sense equal to the
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* actual length of the data transfer.
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* Changed handling of partial data transfers: they do not
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* cause DMA errors.
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* Moved initiation of DMA transfers to the correct place.
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* Removed reference to unallocated memory.
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* Made __idetape_discard_read_pipeline return the number of
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* sectors skipped, not the number of stages.
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* Replaced errant kfree() calls with __idetape_kfree_stage().
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* Fixed off-by-one error in testing the pipeline length.
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* Fixed handling of filemarks in the read pipeline.
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* Small code optimization for MTBSF and MTBSFM ioctls.
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* Don't try to unlock the door during device close if is
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* already unlocked!
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* Cosmetic fixes to miscellaneous debugging output messages.
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* Set the minimum /proc/ide/hd?/settings values for "pipeline",
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* "pipeline_min", and "pipeline_max" to 1.
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*/
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@ -0,0 +1,146 @@
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/*
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* IDE ATAPI streaming tape driver.
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*
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* This driver is a part of the Linux ide driver.
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*
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* The driver, in co-operation with ide.c, basically traverses the
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* request-list for the block device interface. The character device
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* interface, on the other hand, creates new requests, adds them
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* to the request-list of the block device, and waits for their completion.
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*
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* Pipelined operation mode is now supported on both reads and writes.
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*
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* The block device major and minor numbers are determined from the
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* tape's relative position in the ide interfaces, as explained in ide.c.
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*
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* The character device interface consists of the following devices:
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*
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* ht0 major 37, minor 0 first IDE tape, rewind on close.
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* ht1 major 37, minor 1 second IDE tape, rewind on close.
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* ...
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* nht0 major 37, minor 128 first IDE tape, no rewind on close.
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* nht1 major 37, minor 129 second IDE tape, no rewind on close.
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* ...
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*
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* The general magnetic tape commands compatible interface, as defined by
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* include/linux/mtio.h, is accessible through the character device.
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*
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* General ide driver configuration options, such as the interrupt-unmask
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* flag, can be configured by issuing an ioctl to the block device interface,
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* as any other ide device.
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*
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* Our own ide-tape ioctl's can be issued to either the block device or
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* the character device interface.
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*
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* Maximal throughput with minimal bus load will usually be achieved in the
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* following scenario:
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*
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* 1. ide-tape is operating in the pipelined operation mode.
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* 2. No buffering is performed by the user backup program.
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*
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* Testing was done with a 2 GB CONNER CTMA 4000 IDE ATAPI Streaming Tape Drive.
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*
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* Here are some words from the first releases of hd.c, which are quoted
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* in ide.c and apply here as well:
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*
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* | Special care is recommended. Have Fun!
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*
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*
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* An overview of the pipelined operation mode.
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*
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* In the pipelined write mode, we will usually just add requests to our
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* pipeline and return immediately, before we even start to service them. The
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* user program will then have enough time to prepare the next request while
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* we are still busy servicing previous requests. In the pipelined read mode,
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* the situation is similar - we add read-ahead requests into the pipeline,
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* before the user even requested them.
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*
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* The pipeline can be viewed as a "safety net" which will be activated when
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* the system load is high and prevents the user backup program from keeping up
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* with the current tape speed. At this point, the pipeline will get
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* shorter and shorter but the tape will still be streaming at the same speed.
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* Assuming we have enough pipeline stages, the system load will hopefully
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* decrease before the pipeline is completely empty, and the backup program
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* will be able to "catch up" and refill the pipeline again.
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*
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* When using the pipelined mode, it would be best to disable any type of
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* buffering done by the user program, as ide-tape already provides all the
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* benefits in the kernel, where it can be done in a more efficient way.
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* As we will usually not block the user program on a request, the most
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* efficient user code will then be a simple read-write-read-... cycle.
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* Any additional logic will usually just slow down the backup process.
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*
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* Using the pipelined mode, I get a constant over 400 KBps throughput,
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* which seems to be the maximum throughput supported by my tape.
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*
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* However, there are some downfalls:
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*
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* 1. We use memory (for data buffers) in proportional to the number
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* of pipeline stages (each stage is about 26 KB with my tape).
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* 2. In the pipelined write mode, we cheat and postpone error codes
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* to the user task. In read mode, the actual tape position
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* will be a bit further than the last requested block.
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*
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* Concerning (1):
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*
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* 1. We allocate stages dynamically only when we need them. When
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* we don't need them, we don't consume additional memory. In
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* case we can't allocate stages, we just manage without them
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* (at the expense of decreased throughput) so when Linux is
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* tight in memory, we will not pose additional difficulties.
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*
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* 2. The maximum number of stages (which is, in fact, the maximum
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* amount of memory) which we allocate is limited by the compile
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* time parameter IDETAPE_MAX_PIPELINE_STAGES.
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*
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* 3. The maximum number of stages is a controlled parameter - We
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* don't start from the user defined maximum number of stages
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* but from the lower IDETAPE_MIN_PIPELINE_STAGES (again, we
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* will not even allocate this amount of stages if the user
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* program can't handle the speed). We then implement a feedback
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* loop which checks if the pipeline is empty, and if it is, we
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* increase the maximum number of stages as necessary until we
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* reach the optimum value which just manages to keep the tape
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* busy with minimum allocated memory or until we reach
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* IDETAPE_MAX_PIPELINE_STAGES.
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*
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* Concerning (2):
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*
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* In pipelined write mode, ide-tape can not return accurate error codes
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* to the user program since we usually just add the request to the
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* pipeline without waiting for it to be serviced. In case an error
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* occurs, I will report it on the next user request.
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*
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* In the pipelined read mode, subsequent read requests or forward
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* filemark spacing will perform correctly, as we preserve all blocks
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* and filemarks which we encountered during our excess read-ahead.
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*
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* For accurate tape positioning and error reporting, disabling
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* pipelined mode might be the best option.
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*
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* You can enable/disable/tune the pipelined operation mode by adjusting
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* the compile time parameters below.
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*
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*
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* Possible improvements.
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*
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* 1. Support for the ATAPI overlap protocol.
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*
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* In order to maximize bus throughput, we currently use the DSC
|
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* overlap method which enables ide.c to service requests from the
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* other device while the tape is busy executing a command. The
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* DSC overlap method involves polling the tape's status register
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* for the DSC bit, and servicing the other device while the tape
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* isn't ready.
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*
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* In the current QIC development standard (December 1995),
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* it is recommended that new tape drives will *in addition*
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* implement the ATAPI overlap protocol, which is used for the
|
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* same purpose - efficient use of the IDE bus, but is interrupt
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* driven and thus has much less CPU overhead.
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*
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* 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.
|
||||
*/
|
||||
|
|
@ -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"
|
||||
|
|
|
|||
Loading…
Reference in New Issue