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Significant upgrades to sa(4) and mt(1). The primary focus of these changes is to modernize FreeBSD's tape infrastructure so that we can take advantage of some of the features of modern tape drives and allow support for LTFS. Significant changes and new features include: o sa(4) driver status and parameter information is now exported via an XML structure. This will allow for changes and improvements later on that will not break userland applications. The old MTIOCGET status ioctl remains, so applications using the existing interface will not break. o 'mt status' now reports drive-reported tape position information as well as the previously available calculated tape position information. These numbers will be different at times, because the drive-reported block numbers are relative to BOP (Beginning of Partition), but the block numbers calculated previously via sa(4) (and still provided) are relative to the last filemark. Both numbers are now provided. 'mt status' now also shows the drive INQUIRY information, serial number and any position flags (BOP, EOT, etc.) provided with the tape position information. 'mt status -v' adds information on the maximum possible I/O size, and the underlying values used to calculate it. o The extra sa(4) /dev entries (/dev/saN.[0-3]) have been removed. The extra devices were originally added as place holders for density-specific device nodes. Some OSes (NetBSD, NetApp's OnTap and Solaris) have had device nodes that, when you write to them, will automatically select a given density for particular tape drives. This is a convenient way of switching densities, but it was never implemented in FreeBSD. Only the device nodes were there, and that sometimes confused users. For modern tape devices, the density is generally not selectable (e.g. with LTO) or defaults to the highest availble density when the tape is rewritten from BOT (e.g. TS11X0). So, for most users, density selection won't be necessary. If they do need to select the density, it is easy enough to use 'mt density' to change it. o Protection information is now supported. This is either a Reed-Solomon CRC or CRC32 that is included at the end of each block read and written. On write, the tape drive verifies the CRC, and on read, the tape drive provides a CRC for the userland application to verify. o New, extensible tape driver parameter get/set interface. o Density reporting information. For drives that support it, 'mt getdensity' will show detailed information on what formats the tape drive supports, and what formats the tape drive supports. o Some mt(1) functionality moved into a new mt(3) library so that external applications can reuse the code. o The new mt(3) library includes helper routines to aid in parsing the XML output of the sa(4) driver, and build a tree of driver metadata. o Support for the MTLOAD (load a tape in the drive) and MTWEOFI (write filemark immediate) ioctls needed by IBM's LTFS implementation. o Improve device departure behavior for the sa(4) driver. The previous implementation led to hangs when the device was open. o This has been tested on the following types of drives: IBM TS1150 IBM TS1140 IBM LTO-6 IBM LTO-5 HP LTO-2 Seagate DDS-4 Quantum DLT-4000 Exabyte 8505 Sony DDS-2 contrib/groff/tmac/doc-syms, share/mk/bsd.libnames.mk, lib/Makefile, Add libmt. lib/libmt/Makefile, lib/libmt/mt.3, lib/libmt/mtlib.c, lib/libmt/mtlib.h, New mt(3) library that contains functions moved from mt(1) and new functions needed to interact with the updated sa(4) driver. This includes XML parser helper functions that application writers can use when writing code to query tape parameters. rescue/rescue/Makefile: Add -lmt to CRUNCH_LIBS. src/share/man/man4/mtio.4 Clarify this man page a bit, and since it contains what is essentially the mtio.h header file, add new ioctls and structure definitions from mtio.h. src/share/man/man4/sa.4 Update BUGS and maintainer section. sys/cam/scsi/scsi_all.c, sys/cam/scsi/scsi_all.h: Add SCSI SECURITY PROTOCOL IN/OUT CDB definitions and CDB building functions. sys/cam/scsi/scsi_sa.c sys/cam/scsi/scsi_sa.h Many tape driver changes, largely outlined above. Increase the sa(4) driver read/write timeout from 4 to 32 minutes. This is based on the recommended values for IBM LTO 5/6 drives. This may also avoid timeouts for other tape hardware that can take a long time to do retries and error recovery. Longer term, a better way to handle this is to ask the drive for recommended timeout values using the REPORT SUPPORTED OPCODES command. Modern IBM and Oracle tape drives at least support that command, and it would allow for more accurate timeout values. Add XML status generation. This is done with a series of macros to eliminate as much duplicate code as possible. The new XML-based status values are reported through the new MTIOCEXTGET ioctl. Add XML driver parameter reporting, using the new MTIOCPARAMGET ioctl. Add a new driver parameter setting interface, using the new MTIOCPARAMSET and MTIOCSETLIST ioctls. Add a new MTIOCRBLIM ioctl to get block limits information. Add CCB/CDB building routines scsi_locate_16, scsi_locate_10, and scsi_read_position_10(). scsi_locate_10 implements the LOCATE command, as does the existing scsi_set_position() command. It just supports additional arguments and features. If/when we figure out a good way to provide backward compatibility for older applications using the old function API, we can just revamp scsi_set_position(). The same goes for scsi_read_position_10() and the existing scsi_read_position() function. Revamp sasetpos() to take the new mtlocate structure as an argument. It now will use either scsi_locate_10() or scsi_locate_16(), depending upon the arguments the user supplies. As before, once we change position we don't have a clear idea of what the current logical position of the tape drive is. For tape drives that support long form position data, we read the current position and store that for later reporting after changing the position. This should help applications like Bacula speed tape access under FreeBSD once they are modified to support the new ioctls. Add a new quirk, SA_QUIRK_NO_LONG_POS, that is set for all drives that report SCSI-2 or older, as well as drives that report an Illegal Request type error for READ POSITION with the long format. So we should automatically detect drives that don't support the long form and stop asking for it after an initial try. Add a partition number to the sa(4) softc. Improve device departure handling. The previous implementation led to hangs when the device was open. If an application had the sa(4) driver open, and attempted to close it after it went away, the cam_periph_release() call in saclose() would cause the periph to get destroyed because that was the last reference to it. Because destroy_dev() was called from the sa(4) driver's cleanup routine (sacleanup()), and would block waiting for the close to happen, a deadlock would result. So instead of calling destroy_dev() from the cleanup routine, call destroy_dev_sched_cb() from saoninvalidate() and wait for the callback. Acquire a reference for devfs in saregister(), and release it in the new sadevgonecb() routine when all devfs devices for the particular sa(4) driver instance are gone. Add a new function, sasetupdev(), to centralize setting per-instance devfs device parameters instead of repeating the code in saregister(). Add an open count to the softc, so we know how many peripheral driver references are a result of open sessions. Add the D_TRACKCLOSE flag to the cdevsw flags so that we get a 1:1 mapping of open to close calls instead of a N:1 mapping. This should be a no-op for everything except the control device, since we don't allow more than one open on non-control devices. However, since we do allow multiple opens on the control device, the combination of the open count and the D_TRACKCLOSE flag should result in an accurate peripheral driver reference count, and an accurate open count. The accurate open count allows us to release all peripheral driver references that are the result of open contexts once we get the callback from devfs. sys/sys/mtio.h: Add a number of new mt(4) ioctls and the requisite data structures. None of the existing interfaces been removed or changed. This includes definitions for the following new ioctls: MTIOCRBLIM /* get block limits */ MTIOCEXTLOCATE /* seek to position */ MTIOCEXTGET /* get tape status */ MTIOCPARAMGET /* get tape params */ MTIOCPARAMSET /* set tape params */ MTIOCSETLIST /* set N params */ usr.bin/mt/Makefile: mt(1) now depends on libmt, libsbuf and libbsdxml. usr.bin/mt/mt.1: Document new mt(1) features and subcommands. usr.bin/mt/mt.c: Implement support for mt(1) subcommands that need to use getopt(3) for their arguments. Implement a new 'mt status' command to replace the old 'mt status' command. The old status command has been renamed 'ostatus'. The new status function uses the MTIOCEXTGET ioctl, and therefore parses the XML data to determine drive status. The -x argument to 'mt status' allows the user to dump out the raw XML reported by the kernel. The new status display is mostly the same as the old status display, except that it doesn't print the redundant density mode information, and it does print the current partition number and position flags. Add a new command, 'mt locate', that will supersede the old 'mt setspos' and 'mt sethpos' commands. 'mt locate' implements all of the functionality of the MTIOCEXTLOCATE ioctl, and allows the user to change the logical position of the tape drive in a number of ways. (Partition, block number, file number, set mark number, end of data.) The immediate bit and the explicit address bits are implemented, but not documented in the man page. Add a new 'mt weofi' command to use the new MTWEOFI ioctl. This allows the user to ask the drive to write a filemark without waiting around for the operation to complete. Add a new 'mt getdensity' command that gets the XML-based tape drive density report from the sa(4) driver and displays it. This uses the SCSI REPORT DENSITY SUPPORT command to get comprehensive information from the tape drive about what formats it is able to read and write. Add a new 'mt protect' command that allows getting and setting tape drive protection information. The protection information is a CRC tacked on to the end of every read/write from and to the tape drive. Sponsored by: Spectra Logic MFC after: 1 month
2015-02-23 21:59:30 +00:00
.\"
.\" Copyright (c) 2013, 2015 Spectra Logic Corporation
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions, and the following disclaimer,
.\" without modification.
.\" 2. Redistributions in binary form must reproduce at minimum a disclaimer
.\" substantially similar to the "NO WARRANTY" disclaimer below
.\" ("Disclaimer") and any redistribution must be conditioned upon
.\" including a substantially similar Disclaimer requirement for further
.\" binary redistribution.
.\"
.\" NO WARRANTY
.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
.\" "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
.\" LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR
.\" A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
.\" HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
.\" IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
.\" POSSIBILITY OF SUCH DAMAGES.
.\"
.\" Authors: Ken Merry (Spectra Logic Corporation)
.\"
.\" $FreeBSD$
.\"
.Dd February 13, 2015
.Dt MT 3
.Os
.Sh NAME
.Nm mt_start_element ,
.Nm mt_end_element ,
.Nm mt_char_handler ,
.Nm mt_status_tree_sbuf ,
.Nm mt_status_tree_print ,
.Nm mt_status_entry_free ,
.Nm mt_status_free ,
.Nm mt_entry_sbuf ,
.Nm mt_param_parent_print ,
.Nm mt_param_entry_print ,
.Nm mt_protect_print ,
.Nm mt_param_list ,
.Nm mt_density_name ,
.Nm mt_density_bp ,
.Nm mt_density_num ,
.Nm mt_get_xml_str ,
.Nm mt_get_status
.Nd Magnetic Tape library
.Sh LIBRARY
.Lb libmt
.Sh SYNOPSIS
.In sys/sbuf.h
.In bsdxml.h
.In mtlib.h
.Ft void
.Fo mt_start_element
.Fa "void *user_data"
.Fa "const char *name"
.Fa "const char **attr"
.Fc
.Ft void
.Fo mt_end_element
.Fa "void *user_data"
.Fa "const char *name"
.Fc
.Ft void
.Fo mt_char_handler
.Fa "void *user_data"
.Fa "const XML_Char *str"
.Fa "int len"
.Fc
.Ft void
.Fo mt_status_tree_sbuf
.Fa "struct sbuf *sb"
.Fa "struct mt_status_entry *entry"
.Fa "int indent"
.Fa "void (*sbuf_func)(struct sbuf *sb, struct mt_status_entry *entry, void *arg)"
.Fa "void *arg"
.Fc
.Ft void
.Fo mt_status_tree_print
.Fa "struct mt_status_entry *entry"
.Fa "int indent"
.Fa "void (*print_func)(struct mt_status_entry *entry, void *arg)"
.Fa "void *arg"
.Fc
.Ft "struct mt_status_entry *"
.Fo mt_entry_find
.Fa "struct mt_status_entry *entry"
.Fa "char *name"
.Fc
.Ft "struct mt_status_entry *"
.Fo mt_status_entry_find
.Fa "struct mt_status_data *status_data"
.Fa "char *name"
.Fc
.Ft void
.Fo mt_status_entry_free
.Fa "struct mt_status_entry *entry)"
.Fc
.Ft void
.Fo mt_status_free
.Fa "struct mt_status_data *status_data"
.Fc
.Ft void
.Fo mt_entry_sbuf
.Fa "struct sbuf *sb"
.Fa "struct mt_status_entry *entry"
.Fa "char *fmt"
.Fc
.Ft void
.Fo mt_param_parent_sbuf
.Fa "struct sbuf *sb"
.Fa "struct mt_status_entry *entry"
.Fa "struct mt_print_params *print_params"
.Fc
.Ft void
.Fo mt_param_parent_print
.Fa "struct mt_status_entry *entry"
.Fa "struct mt_print_params *print_params"
.Fc
.Ft void
.Fo mt_param_entry_sbuf
.Fa "struct sbuf *sb"
.Fa "struct mt_status_entry *entry"
.Fa "void *arg"
.Fc
.Ft void
.Fo mt_param_entry_print
.Fa "struct mt_status_entry *entry"
.Fa "void *arg"
.Fc
.Ft int
.Fo mt_protect_print
.Fa "struct mt_status_data *status_data"
.Fa "int verbose"
.Fc
.Ft int
.Fo mt_param_list
.Fa "struct mt_status_data *status_data"
.Fa "char *param_name"
.Fa "int quiet"
.Fc
.Ft "const char *"
.Fo mt_density_name
.Fa "int density_num"
.Fc
.Ft int
.Fo mt_density_bp
.Fa "int density_num"
.Fa "int bpi"
.Fc
.Ft int
.Fo mt_density_num
.Fa "const char *density_name"
.Fc
.Ft int
.Fo mt_get_status
.Fa "char *xml_str"
.Fa "struct mt_status_data *status_data"
.Fc
.Sh DESCRIPTION
The MT library consists of a number of functions designed to aid in
interacting with the
.Xr sa 4
driver.
The
.Xr sa 4
driver returns some status data as XML-formatted strings, and
the primary purpose of this library is to make it easier for the
software developer to parse those strings and extract the status values.
.Pp
The
.Fn mt_start_element ,
.Fn mt_end_element ,
and
.Fn mt_char_handler
functions are designed to work with the
Fix typo. MFC after: 1 month Sponsored by: The FreeBSD Foundation
2016-02-29 17:20:37 +00:00
.Xr libbsdxml 3
Significant upgrades to sa(4) and mt(1). The primary focus of these changes is to modernize FreeBSD's tape infrastructure so that we can take advantage of some of the features of modern tape drives and allow support for LTFS. Significant changes and new features include: o sa(4) driver status and parameter information is now exported via an XML structure. This will allow for changes and improvements later on that will not break userland applications. The old MTIOCGET status ioctl remains, so applications using the existing interface will not break. o 'mt status' now reports drive-reported tape position information as well as the previously available calculated tape position information. These numbers will be different at times, because the drive-reported block numbers are relative to BOP (Beginning of Partition), but the block numbers calculated previously via sa(4) (and still provided) are relative to the last filemark. Both numbers are now provided. 'mt status' now also shows the drive INQUIRY information, serial number and any position flags (BOP, EOT, etc.) provided with the tape position information. 'mt status -v' adds information on the maximum possible I/O size, and the underlying values used to calculate it. o The extra sa(4) /dev entries (/dev/saN.[0-3]) have been removed. The extra devices were originally added as place holders for density-specific device nodes. Some OSes (NetBSD, NetApp's OnTap and Solaris) have had device nodes that, when you write to them, will automatically select a given density for particular tape drives. This is a convenient way of switching densities, but it was never implemented in FreeBSD. Only the device nodes were there, and that sometimes confused users. For modern tape devices, the density is generally not selectable (e.g. with LTO) or defaults to the highest availble density when the tape is rewritten from BOT (e.g. TS11X0). So, for most users, density selection won't be necessary. If they do need to select the density, it is easy enough to use 'mt density' to change it. o Protection information is now supported. This is either a Reed-Solomon CRC or CRC32 that is included at the end of each block read and written. On write, the tape drive verifies the CRC, and on read, the tape drive provides a CRC for the userland application to verify. o New, extensible tape driver parameter get/set interface. o Density reporting information. For drives that support it, 'mt getdensity' will show detailed information on what formats the tape drive supports, and what formats the tape drive supports. o Some mt(1) functionality moved into a new mt(3) library so that external applications can reuse the code. o The new mt(3) library includes helper routines to aid in parsing the XML output of the sa(4) driver, and build a tree of driver metadata. o Support for the MTLOAD (load a tape in the drive) and MTWEOFI (write filemark immediate) ioctls needed by IBM's LTFS implementation. o Improve device departure behavior for the sa(4) driver. The previous implementation led to hangs when the device was open. o This has been tested on the following types of drives: IBM TS1150 IBM TS1140 IBM LTO-6 IBM LTO-5 HP LTO-2 Seagate DDS-4 Quantum DLT-4000 Exabyte 8505 Sony DDS-2 contrib/groff/tmac/doc-syms, share/mk/bsd.libnames.mk, lib/Makefile, Add libmt. lib/libmt/Makefile, lib/libmt/mt.3, lib/libmt/mtlib.c, lib/libmt/mtlib.h, New mt(3) library that contains functions moved from mt(1) and new functions needed to interact with the updated sa(4) driver. This includes XML parser helper functions that application writers can use when writing code to query tape parameters. rescue/rescue/Makefile: Add -lmt to CRUNCH_LIBS. src/share/man/man4/mtio.4 Clarify this man page a bit, and since it contains what is essentially the mtio.h header file, add new ioctls and structure definitions from mtio.h. src/share/man/man4/sa.4 Update BUGS and maintainer section. sys/cam/scsi/scsi_all.c, sys/cam/scsi/scsi_all.h: Add SCSI SECURITY PROTOCOL IN/OUT CDB definitions and CDB building functions. sys/cam/scsi/scsi_sa.c sys/cam/scsi/scsi_sa.h Many tape driver changes, largely outlined above. Increase the sa(4) driver read/write timeout from 4 to 32 minutes. This is based on the recommended values for IBM LTO 5/6 drives. This may also avoid timeouts for other tape hardware that can take a long time to do retries and error recovery. Longer term, a better way to handle this is to ask the drive for recommended timeout values using the REPORT SUPPORTED OPCODES command. Modern IBM and Oracle tape drives at least support that command, and it would allow for more accurate timeout values. Add XML status generation. This is done with a series of macros to eliminate as much duplicate code as possible. The new XML-based status values are reported through the new MTIOCEXTGET ioctl. Add XML driver parameter reporting, using the new MTIOCPARAMGET ioctl. Add a new driver parameter setting interface, using the new MTIOCPARAMSET and MTIOCSETLIST ioctls. Add a new MTIOCRBLIM ioctl to get block limits information. Add CCB/CDB building routines scsi_locate_16, scsi_locate_10, and scsi_read_position_10(). scsi_locate_10 implements the LOCATE command, as does the existing scsi_set_position() command. It just supports additional arguments and features. If/when we figure out a good way to provide backward compatibility for older applications using the old function API, we can just revamp scsi_set_position(). The same goes for scsi_read_position_10() and the existing scsi_read_position() function. Revamp sasetpos() to take the new mtlocate structure as an argument. It now will use either scsi_locate_10() or scsi_locate_16(), depending upon the arguments the user supplies. As before, once we change position we don't have a clear idea of what the current logical position of the tape drive is. For tape drives that support long form position data, we read the current position and store that for later reporting after changing the position. This should help applications like Bacula speed tape access under FreeBSD once they are modified to support the new ioctls. Add a new quirk, SA_QUIRK_NO_LONG_POS, that is set for all drives that report SCSI-2 or older, as well as drives that report an Illegal Request type error for READ POSITION with the long format. So we should automatically detect drives that don't support the long form and stop asking for it after an initial try. Add a partition number to the sa(4) softc. Improve device departure handling. The previous implementation led to hangs when the device was open. If an application had the sa(4) driver open, and attempted to close it after it went away, the cam_periph_release() call in saclose() would cause the periph to get destroyed because that was the last reference to it. Because destroy_dev() was called from the sa(4) driver's cleanup routine (sacleanup()), and would block waiting for the close to happen, a deadlock would result. So instead of calling destroy_dev() from the cleanup routine, call destroy_dev_sched_cb() from saoninvalidate() and wait for the callback. Acquire a reference for devfs in saregister(), and release it in the new sadevgonecb() routine when all devfs devices for the particular sa(4) driver instance are gone. Add a new function, sasetupdev(), to centralize setting per-instance devfs device parameters instead of repeating the code in saregister(). Add an open count to the softc, so we know how many peripheral driver references are a result of open sessions. Add the D_TRACKCLOSE flag to the cdevsw flags so that we get a 1:1 mapping of open to close calls instead of a N:1 mapping. This should be a no-op for everything except the control device, since we don't allow more than one open on non-control devices. However, since we do allow multiple opens on the control device, the combination of the open count and the D_TRACKCLOSE flag should result in an accurate peripheral driver reference count, and an accurate open count. The accurate open count allows us to release all peripheral driver references that are the result of open contexts once we get the callback from devfs. sys/sys/mtio.h: Add a number of new mt(4) ioctls and the requisite data structures. None of the existing interfaces been removed or changed. This includes definitions for the following new ioctls: MTIOCRBLIM /* get block limits */ MTIOCEXTLOCATE /* seek to position */ MTIOCEXTGET /* get tape status */ MTIOCPARAMGET /* get tape params */ MTIOCPARAMSET /* set tape params */ MTIOCSETLIST /* set N params */ usr.bin/mt/Makefile: mt(1) now depends on libmt, libsbuf and libbsdxml. usr.bin/mt/mt.1: Document new mt(1) features and subcommands. usr.bin/mt/mt.c: Implement support for mt(1) subcommands that need to use getopt(3) for their arguments. Implement a new 'mt status' command to replace the old 'mt status' command. The old status command has been renamed 'ostatus'. The new status function uses the MTIOCEXTGET ioctl, and therefore parses the XML data to determine drive status. The -x argument to 'mt status' allows the user to dump out the raw XML reported by the kernel. The new status display is mostly the same as the old status display, except that it doesn't print the redundant density mode information, and it does print the current partition number and position flags. Add a new command, 'mt locate', that will supersede the old 'mt setspos' and 'mt sethpos' commands. 'mt locate' implements all of the functionality of the MTIOCEXTLOCATE ioctl, and allows the user to change the logical position of the tape drive in a number of ways. (Partition, block number, file number, set mark number, end of data.) The immediate bit and the explicit address bits are implemented, but not documented in the man page. Add a new 'mt weofi' command to use the new MTWEOFI ioctl. This allows the user to ask the drive to write a filemark without waiting around for the operation to complete. Add a new 'mt getdensity' command that gets the XML-based tape drive density report from the sa(4) driver and displays it. This uses the SCSI REPORT DENSITY SUPPORT command to get comprehensive information from the tape drive about what formats it is able to read and write. Add a new 'mt protect' command that allows getting and setting tape drive protection information. The protection information is a CRC tacked on to the end of every read/write from and to the tape drive. Sponsored by: Spectra Logic MFC after: 1 month
2015-02-23 21:59:30 +00:00
library, which is an XML parsing library.
The user data for the XML parser should be set with
.Fn XML_SetUserData
to a zeroed struct
mt_status_data with the entries list initialized.
The element handlers for the XML parser should be set to
.Fn mt_start_element
and
.Fn mt_end_element
with
.Fn XML_SetElementHandler .
The character data handler should be set to
.Fn mt_char_handler
with the
.Fn XML_SetCharacterDataHandler
function.
The error member of the status_data structure will be set to 0 if parsing
is successful, and non-zero if parsing failed.
In the event of a failure, the error_str member will contain an error
message describing the failure.
These functions will build a tree of tape driver status data that can be
searched and printed using the other functions in this library.
.Pp
.Fn mt_status_tree_sbuf
takes the root node of a tree of
.Xr sa 4
driver status information, and displays it in an
.Xr sbuf 9 .
The
.Ar sb
argument is the destination sbuf.
The
.Ar entry
argument is the root of the tree.
The
.Ar indent
argument is the number of characters to indent the output.
Each recursive call to
.Fn mt_status_tree_sbuf
will have the indent level incremented by 2.
The
.Ar sbuf_func
argument is for a user-supplied alternate printing function.
If it is non-NULL, it will be called instead of the default output printing
code.
The
.Ar arg
argument is an argument for the
.Ar sbuf_func
function.
.Pp
The
.Fn mt_status_tree_print
function is the same as the
.Fn mt_status_tree_sbuf
function, except that the tree is printed to standard out instead of to a
sbuf.
.Pp
The
.Fn mt_entry_find
function returns the first entry in the tree starting at
.Ar entry
that matches
.Ar name .
The supplied node name can be a single level name like "foo", or it can
specify mulitple node names that must be matched, for instance "foo.bar.baz".
In the case of a single level name, it will match any node beneath
.Ar entry
that matches
.Ar name .
In the case of a multi-level name like "foo.bar.baz", it will return the
first entry named "baz" whose immediate parent is "bar" and where the
parent of "bar" is named "foo".
.Pp
The
.Fn mt_status_entry_find
is the same as
.Fn mt_entry_find ,
except that it operates on the top level mt_status_data and all
mt_status_entry nodes below it instead of just an mt_status_entry
structure.
.Pp
The
.Fn mt_status_entry_free
function frees the tree of status data underneath
.Ar entry .
.Pp
The
.Fn mt_status_free
function frees the tree of status data underneath
.Ar status_data .
.Pp
The
.Fn mt_entry_sbuf
function prints
.Ar entry
to the supplied sbuf
.Ar sb ,
optionally using the
.Xr printf 3
format
.Ar fmt .
If
.Ar fmt
is NULL, then
.Fn mt_entry_sbuf
will render integer types in base 10 without special formatting and all
other types as they were rendered in the XML.
.Pp
.Fn mt_param_parent_sbuf
prints the parents of the given
.Ar entry
to the supplied sbuf
.Ar sb
subject to the print parameters
.Ar print_params .
The result will be formatted with a period between each level, like
"foo.bar.baz".
.Pp
.Fn mt_param_parent_print
is like
.Fn mt_param_parent_sbuf
except that it prints the results to standard output instead of an sbuf.
.Pp
.Fn mt_param_entry_sbuf
prints the
.Ar entry
to the given sbuf
.Ar sb .
The argument
.Ar arg
is a pointer to struct mt_print_params, which allows the caller to control
the printing output.
This function is intended to be supplied as an argument to
.Fn mt_status_tree_sbuf .
.Pp
.Fn mt_param_entry_print
is like
.Fn mt_param_entry_sbuf
except that it prints to standard output instead of an sbuf.
It is intended to be used as an argument to
.Fn mt_status_tree_print .
.Pp
.Fn mt_protect_print
prints tape drive protection information from the supplied
.Ar status_data
beginning at the node name defined as the root node for protection data.
If the
.Ar verbose
argument is non-zero, protection entry descriptions will be printed.
If it is zero, protection entry descriptions will not be printed.
.Pp
.Fn mt_param_list
prints tape driver parameters information from the supplied
.Ar status_data .
If the
.Ar param_name
is non-NULL, only the named parameter will be printed.
If
.Ar quiet
is non-zero, parameter descriptions will be omitted in the output.
.Pp
.Fn mt_density_name
Returns a text identifier for the supplied numeric
.Ar density_num .
The
.Ar density_num
should currently be a value between 0 and 255 inclusive, since that is the
valid range for
.Tn SCSI
density code values.
See below for notes on the return values.
.Pp
.Fn mt_density_bp
Returns the bits per inch or bits per mm values for a given density entry
specified by the
.Ar density_num .
If the
.Ar bpi
argument is non-zero, the bits per inch value is returned.
Otherwise, the bits per mm value is returned.
.Pp
.Fn mt_density_num
returns a numeric value for a text density description.
It does a case-insensitive comparison of density names in the density table
to the supplied density name.
.Pp
.Fn mt_get_xml_str
gets the current XML status / parameter string from the sa(4) driver
instance referenced by the open file descriptor
.Ar mtfd .
The
.Xr mtio 4
.Xr ioctl 2
to be used is supplied as the
.Ar cmd
argument.
Currently the
.Fn mt_get_xml_str
function will work with the
.Dv MTIOCEXTGET
and
.Dv MTIOCPARAMGET
ioctls.
The supplied
.Ar xml_str
will be filled in with a pointer to the complete XML status string.
Multiple calls to the given
.Xr ioctl 2
are made and more space is malloced until all of the XML string is fetched.
The string returned in the
.Ar xml_str
argument should be freed when it is no longer in use.
.Sh RETURN VALUES
.Fn mt_entry_find
returns the first matching entry, or NULL if it fails to find a match.
.Pp
.Fn mt_status_entry_find
returns the first matching entry, or NULL if it fails to find a match.
.Pp
.Fn mt_protect_print
Returns 0 for success, and non-zero for failure.
.Fn mt_protect_print
can only fail if it cannot find protection information in the supplied
status data.
.Pp
.Fn mt_param_list
Returns 0 for success and non-zero for failure.
.Fn mt_param_list
can only fail if it cannot find parameter information in the supplied
status data.
.Pp
.Fn mt_density_name
returns a text description of a numeric density.
The special density value 0 is decoded as "default".
The special density value 0x7f is decoded as "same".
If the density is not known,
.Fn mt_density_name
will return "UNKNOWN".
.Pp
.Fn mt_density_bp
returns the bits per inch value for the given density (if the
.Ar bpi
field is non-zero), the bits per mm value otherwise, or 0 if the supplied
.Ar density_num
is not in the density table or the table entry does not include bpi / bpmm
values.
.Pp
.Fn mt_density_num
returns a numeric density value between 0 and 255 for the supplied density
name.
It returns 0 if the density name is not recognized.
.Pp
.Fn mt_get_xml_str
returns 0 for success, and -1 for failure.
.Sh SEE ALSO
.Xr mt 1 ,
.Xr mtio 4 ,
.Xr sa 4
.Sh HISTORY
The MT library first appeared in
.Fx 10.1 .
.Sh AUTHORS
.An Ken Merry Aq ken@FreeBSD.org
.Sh BUGS
The library interface is not complete, and may change in the future.
Application authors should not rely on the library interface to be
consistent in the immediate future.
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