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-IDE ATAPI streaming tape driver.
-
-This driver is a part of the Linux ide driver.
-
-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.
-
-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.
-...
-
-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.
-
-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!
-
-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.