|
@@ -1,67 +1,65 @@
|
|
|
-/*
|
|
|
- * 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.
|
|
|
- */
|
|
|
+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.
|