forked from rrcarlosr/Jetpack
258 lines
16 KiB
Plaintext
258 lines
16 KiB
Plaintext
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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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