📄 1097-1098.html
字号:
<HTML>
<HEAD>
<TITLE>Linux Complete Command Reference:Special Files:EarthWeb Inc.-</TITLE>
</HEAD>
<META NAME="ROBOTS" CONTENT="NOINDEX, NOFOLLOW">
<SCRIPT>
<!--
function displayWindow(url, width, height) {
var Win = window.open(url,"displayWindow",'width=' + width +
',height=' + height + ',resizable=1,scrollbars=yes');
}
//-->
</SCRIPT>
</HEAD>
-->
<!-- ISBN=0672311046 //-->
<!-- TITLE=Linux Complete Command Reference//-->
<!-- AUTHOR=Red Hat//-->
<!-- PUBLISHER=Macmillan Computer Publishing//-->
<!-- IMPRINT=Sams//-->
<!-- CHAPTER=04 //-->
<!-- PAGES=1063-1102 //-->
<!-- UNASSIGNED1 //-->
<!-- UNASSIGNED2 //-->
<P><CENTER>
<a href="1094-1096.html">Previous</A> | <a href="../ewtoc.html">Table of Contents</A> | <a href="1099-1101.html">Next</A></CENTER></P>
<A NAME="PAGENUM-1097"><P>Page 1097</P></A>
<H3><A NAME="ch04_ 16">
ioctls
</A></H3>
<P>The driver supports three ioctl requests. Requests not recognized by the
st driver are passed to the scsi driver. The definitions below are from
/usr/include/linux/mtio.h:
</P>
<P><B>
MTIOCTOP: Perform a tape operation
</B></P>
<P>This request takes an argument of type (struct mtop
*). Not all drives support all operations. The driver returns an
EIO error if the drive rejects an operation.
</P>
<!-- CODE //-->
<PRE>
/* Structure for MTIOCTOP _ mag tape op command: */
struct mtop {
short mt_op; /* operations defined below */
int mt_count; /* how many of them */
};
</PRE>
<!-- END CODE //-->
<P>Magnetic tape operations:
</P>
<TABLE>
<TR><TD>
MTBSF
</TD><TD>
Backward space over mt_count filemarks.
</TD></TR><TR><TD>
MTBSFM
</TD><TD>
Backward space over mt_count filemarks. Reposition the tape to the
EOT side of the last filemark.
</TD></TR><TR><TD>
MTBSR
</TD><TD>
Backward space over mt_count records (tape blocks).
</TD></TR><TR><TD>
MTBSS
</TD><TD>
Backward space over mt_count setmarks.
</TD></TR><TR><TD>
MTEOM
</TD><TD>
Go to the end of the recorded media (for appending files).
</TD></TR><TR><TD>
MTERASE
</TD><TD>
Erase tape.
</TD></TR><TR><TD>
MTFSF
</TD><TD>
Forward space over mt_count filemarks.
</TD></TR><TR><TD>
MTFSFM
</TD><TD>
Forward space over mt_count filemarks. Reposition the tape to the
BOT side of the last filemark.
</TD></TR><TR><TD>
MTFSR
</TD><TD>
Forward space over mt_count records (tape blocks).
</TD></TR><TR><TD>
MTFSS
</TD><TD>
Forward space over mt_count setmarks.
</TD></TR><TR><TD>
MTNOP
</TD><TD>
No op; flushes the driver's buffer as a side effect. Should be used
before reading status with MTIOCGET.
</TD></TR><TR><TD>
MTOFFL
</TD><TD>
Rewind and put the drive off line.
</TD></TR><TR><TD>
MTRESET
</TD><TD>
Reset drive.
</TD></TR><TR><TD>
MTRETEN
</TD><TD>
Retention tape.
</TD></TR><TR><TD>
MTREW
</TD><TD>
Rewind.
</TD></TR><TR><TD>
MTSEEK
</TD><TD>
Seek to the tape block number specified in
mt_count. This operation requires either a SCSI-2 drive that supports the
LOCATE command (device-specific address) or a Tandberg-compatible SCSI-1 drive
(Tandberg, Archive Viper, Wangtek,…). The block number should be one that
was previously returned by MTIOCPOS because the number is device-specific.
</TD></TR><TR><TD>
MTSETBLK
</TD><TD>
Set the drive's block length to the value specified in
mt_count. A block length of zero sets the drive to variable block size mode.
</TD></TR><TR><TD>
MTSETDENSITY
</TD><TD>
Set the tape density to the code in
mt_count. Some useful density
codes are
</TD></TR><TR><TD>
</TD><TD>
<!-- CODE //-->
<PRE>
18 0x00 Implicit 0x11 QIC-525
0x04 QIC-11 0x12 QIC-1350
0x05 QIC-24 0x13 DDS
0x0F QIC-120 0x14 Exabyte EXB-8200
0x10 QIC-150 0x15 Exabyte EXB-8500
</PRE>
<!-- END CODE //-->
</TD></TR><TR><TD>
MTWEOF
</TD><TD>
Write mt_count filemarks.
</TD></TR><TR><TD>
MTWSM
</TD><TD>
Write mt_count setmarks.
</TD></TR></TABLE>
<A NAME="PAGENUM-1098"><P>Page 1098</P></A>
<TABLE>
<TR><TD>
MTSETDRVBUFFER
</TD><TD>
Set various drive and driver options according to bits encoded
in mt_count. These consist of the drive's buffering mode, six Boolean
driver options, and the buffer write threshold. These parameters are
initialized only when the device is first detected. The settings persist when the
device is closed and reopened. A single operation can affect just the
buffering mode, just the Boolean options, or just the write threshold.
</TD></TR><TR><TD>
</TD><TD>
A value having zeros in the high-order 4 bits will be used to set the
drive's buffering mode. The buffering modes are:
</TD></TR><TR><TD>
</TD><TD>
<!-- CODE //-->
<PRE>
0 The drive will not report GOOD status on write commands
until the data blocks are actually written to the medium.
1 The drive may report GOOD status on write commands as
soon as all the data has been transferred to the drive's
internal buffer.
2 The drive may report GOOD status on write commands as
soon as all the data has been transferred to the drive's internal
buffer and all buffered data from different initiators has
been successfully written to the medium.
</PRE>
<!-- END CODE //-->
</TD></TR><TR><TD>
</TD><TD>
To control the write threshold, the value in
mt_count must include the constant
MT_ST_WRITE_THRESHOLD logically ORed with a block count in
the low 28 bits. The block count refers to 1024-byte blocks, not the
physical block size on the tape. The threshold cannot exceed the driver's
internal buffer size (see the description).
</TD></TR><TR><TD>
</TD><TD>
To set and clear the Boolean options, the value in
mt_count must include the constant MT_ST_BOOLEANS logically ORed with whatever
combination of the following options is desired. Any options not specified are set
false. The Boolean options are
</TD></TR><TR><TD>
MT_ST_BUFFER_WRITES
</TD><TD>
(Default: true) Buffer all write operations. If this option is false and
the drive uses a fixed block size, then all write operations must be for
a multiple of the block size. This option must be set false to write
reliable multi-volume archives.
</TD></TR><TR><TD>
MT_ST_ASYNC_WRITES
</TD><TD>
(Default: true) When this options is true, write operations
return immediately without waiting for the data to be transferred to the drive
if the data fits into the driver's buffer. The write threshold determines
how full the buffer must be before a new SCSI write command is issued.
Any errors reported by the drive will be held until the next operation.
This option must be set false to write reliable multi-volume archives.
</TD></TR><TR><TD>
MT_ST_READ_AHEAD
</TD><TD>
(Default: true) This option causes the driver to provide read
buffering and read-ahead. If this option is false and the drive uses a fixed block
size, then all read operations must be for a multiple of the block size.
</TD></TR><TR><TD>
MT_ST_TWO_FM
</TD><TD>
(Default: false) This option modifies the driver behavior when a file
is closed. The normal action is to write a single filemark. If the option
is true, the driver will write two filemarks and backspace over the <BR>
second one.
</TD></TR><TR><TD>
</TD><TD>
Note that this option should not be set true for QIC tape drives
because they are unable to overwrite a filemark. These drives detect the end
of recorded data by testing for blank tape rather than two
consecutive filemarks.
</TD></TR><TR><TD>
MT_ST_DEBUGGING
</TD><TD>
(Default: false) This option turns on various debugging messages
from the driver (effective only if the driver was compiled with
DEBUG defined).
</TD></TR><TR><TD>
MT_ST_FAST_EOM
</TD><TD>
(Default: false) This option causes the
MTEOM operation to be sent directly to the drive, potentially speeding up the operation but causing the
driver
</TD></TR></TABLE>
<P><CENTER>
<a href="1094-1096.html">Previous</A> | <a href="../ewtoc.html">Table of Contents</A> | <a href="1099-1101.html">Next</A></CENTER></P>
</td>
</tr>
</table>
<!-- begin footer information -->
</body></html>⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -