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author | Linus Torvalds <torvalds@linux-foundation.org> | 2019-07-09 22:34:26 +0300 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-07-09 22:34:26 +0300 |
commit | e9a83bd2322035ed9d7dcf35753d3f984d76c6a5 (patch) | |
tree | 66dc466ff9aec0f9bb7f39cba50a47eab6585559 /Documentation/ide/ide-tape.rst | |
parent | 7011b7e1b702cc76f9e969b41d9a95969f2aecaa (diff) | |
parent | 454f96f2b738374da4b0a703b1e2e7aed82c4486 (diff) | |
download | linux-e9a83bd2322035ed9d7dcf35753d3f984d76c6a5.tar.xz |
Merge tag 'docs-5.3' of git://git.lwn.net/linux
Pull Documentation updates from Jonathan Corbet:
"It's been a relatively busy cycle for docs:
- A fair pile of RST conversions, many from Mauro. These create more
than the usual number of simple but annoying merge conflicts with
other trees, unfortunately. He has a lot more of these waiting on
the wings that, I think, will go to you directly later on.
- A new document on how to use merges and rebases in kernel repos,
and one on Spectre vulnerabilities.
- Various improvements to the build system, including automatic
markup of function() references because some people, for reasons I
will never understand, were of the opinion that
:c:func:``function()`` is unattractive and not fun to type.
- We now recommend using sphinx 1.7, but still support back to 1.4.
- Lots of smaller improvements, warning fixes, typo fixes, etc"
* tag 'docs-5.3' of git://git.lwn.net/linux: (129 commits)
docs: automarkup.py: ignore exceptions when seeking for xrefs
docs: Move binderfs to admin-guide
Disable Sphinx SmartyPants in HTML output
doc: RCU callback locks need only _bh, not necessarily _irq
docs: format kernel-parameters -- as code
Doc : doc-guide : Fix a typo
platform: x86: get rid of a non-existent document
Add the RCU docs to the core-api manual
Documentation: RCU: Add TOC tree hooks
Documentation: RCU: Rename txt files to rst
Documentation: RCU: Convert RCU UP systems to reST
Documentation: RCU: Convert RCU linked list to reST
Documentation: RCU: Convert RCU basic concepts to reST
docs: filesystems: Remove uneeded .rst extension on toctables
scripts/sphinx-pre-install: fix out-of-tree build
docs: zh_CN: submitting-drivers.rst: Remove a duplicated Documentation/
Documentation: PGP: update for newer HW devices
Documentation: Add section about CPU vulnerabilities for Spectre
Documentation: platform: Delete x86-laptop-drivers.txt
docs: Note that :c:func: should no longer be used
...
Diffstat (limited to 'Documentation/ide/ide-tape.rst')
-rw-r--r-- | Documentation/ide/ide-tape.rst | 68 |
1 files changed, 68 insertions, 0 deletions
diff --git a/Documentation/ide/ide-tape.rst b/Documentation/ide/ide-tape.rst new file mode 100644 index 000000000000..3e061d9c0e38 --- /dev/null +++ b/Documentation/ide/ide-tape.rst @@ -0,0 +1,68 @@ +=============================== +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. |