256 lines
9.1 KiB
Groff
256 lines
9.1 KiB
Groff
.\"
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.\" Copyright (C) 1996
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.\" interface business GmbH
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.\" Tolkewitzer Strasse 49
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.\" D-01277 Dresden
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.\" F.R. Germany
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.\"
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.\" All rights reserved.
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.\"
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.\" Written by Joerg Wunsch <joerg_wunsch@interface-business.de>
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.\"
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY
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.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
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.\" OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
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.\" BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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.\" LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
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.\" USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
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.\" DAMAGE.
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.\"
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.\" $Id: worm.4,v 1.4 1996/04/08 04:18:08 mpp Exp $
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.\" "
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.Dd January 27, 1996
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.Dt WORM 4
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.Os FreeBSD
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.Sh NAME
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.Nm worm
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.Nd write-once (CD-R) disk driver
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.Sh SYNOPSIS
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.Cd disk worm0
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.Cd disk worm0 target 5 lun 0
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.Sh DESCRIPTION
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The
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.Nm worm
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driver provides support for a
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.Em SCSI
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write-once device, in particular for a CD-R recording device. The
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driver attempts to abstract the dirty hardware work to a common API as
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good as possible. Due to the very special nature of CD-R devices and
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their handling requirements, this API applies some more constraints to
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the user than those of other disk-like devices.
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.Pp
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A CD is usually structured into sessions and tracks. Each track can
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hold a different type of data, basically either audio information, or
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CD-ROM data. In order to record a CD-R, the device must be told which
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kind of data is to be recorded, at which speed, etc. Once all tracks
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of a session have been written, the medium must finally be
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.Em fixated
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which basically means that the table of contents will be written, and
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the session is marked as usable. Optionally, a new session can be
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enabled at this time, or the disk can be entirely closed to prevent
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further writing.
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.Pp
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One particular feature of all existing CD-R recorders is that they
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require a constant data stream while the write channel is open. This
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usually requires some precautions like using a multiple-buffering
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filter to read the data from the disk, and/or running at real-time
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priority.
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.Pp
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There is no official standard for CD-R devices, so every vendor seems
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to implement his own set of controlling commands. Some vendors use
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rather similar command sets, while other devices behave entirely
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different. The driver has builtin knowledge about the odds and ends
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of some devices, which must then be selected first at run-time in
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order to make the driver operational at all. This builtin knowledge
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will be replaced by a loadable module scenario in the future.
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.Pp
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Due to the requirement of adjusting several parameters before actually
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being able to write some data to the CD-R, and due to the tight timing
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requirements when writing data, the driver distinguishes two different
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operation modes. When opening a file descriptor for a device belonging
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to the
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.Nm
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driver without write access, the driver does not enforce the tight
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timing that is needed to write data to the CD-R, but it allows for
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sending
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.Xr ioctl 2
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commands to adjust parameters. Any number of ioctls can be performed
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on the device as long as the required sequence of actions is being
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maintained. The first thing that must be done is to select a set of
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quirks for the actual device. Then, the per-session parameters must
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be specified. Each track requires a set of per-track parameters
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finally.
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.Pp
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Once all preparations have been done, the device can be opened with
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write intent, at which point the driver starts to activate the
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time-critical handling, and is expecting any number of
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.Xr write 2
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system calls that is required in order to transfer all the data to the
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device. Failure in providing these data in a timely fashion will render
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the current medium unusable. The device-specific sequence for telling
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that the current track is finally complete will be issued to the device
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when calling
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.Xr close 2
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on the file descriptor that has been used to write the data.
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.Pp
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After this happened, things are no longer time-critical. Any number of
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further tracks can be written to the device. Finally, the session must
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be fixated by another ioctl.
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.Sh IOCTLS
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The following
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.Xr ioctl 2
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calls apply to CD-R devices. Their declaration can be found in the
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header file
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.Pa <sys/wormio.h> .
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.Bl -tag -width WORMIOCQUIRKSELECT
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.It Dv WORMIOCQUIRKSELECT
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Select the set of quirk functions to use for this device. This is the
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only allowed action on a virgin device after booting. The argument
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structure takes a vendor and a model string, which are matched against
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the vendor and model strings of all quirk records that have been
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registered with the driver. Currently, the only known quirks must
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have been statically compiled into the driver.
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.Pp
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If the driver fails to match the vendor and model string against any
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known quirk record, the system call returns with an error, and the
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variable
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.Va errno
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will be set to
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.Er EINVAL .
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The system call argument is a pointer to a
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.Dv struct wormio_quirk_select .
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.It Dv WORMIOCPREPDISK
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This command selects several session-wide parameters in the driver.
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The argument structure,
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.Dv struct wormio_prepare_disk
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takes two integer values,
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.Dv dummy ,
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and
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.Dv speed .
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By setting
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.Dv dummy
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to 1, the drive will be told to simulate all actions, without actually
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turning on the laser. It is mainly used to test the environment
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whether it could cope with the timing constraints, without risking a
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damaged medium. The parameter
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.Dv speed
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is device-dependent, where a speed value of one generally applies to
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audio disks, and a speed value of 2 (or more) is used for recording
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data.
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.It Dv WORMIOCPREPTRACK
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The two parameters
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.Dv audio
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and
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.Dv preemp
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are being passed as arguments in a
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.Dv struct wormio_prepare_track .
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Both are Boolean, i.e. can be either 0 or 1. If
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.Dv audio
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is set to 1, the next track will be recorded in audio format, with
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2352 bytes per block. If
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.Dv preemp
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is also set to 1, the audio data are assumed to be recorded with
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preemphasis. If
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.Dv audio
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is 0, CD-ROM data with a block length of 2048 bytes are about to be
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written next.
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.It Dv WORMIOCFIXATION
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This closes the current session. The argument is a pointer to
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.Dv struct wormio_fixation ,
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with the elements
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.Dv toc_type ,
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an integer between 0 and 4, describing the table-of-contents type. See
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.Xr wormcontrol 8
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for a list of useful values. Optionally, setting the field
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.Dv onp
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to 1 will cause the next session being opened, so further recording
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can be performed into the remaining space. If
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.Dv onp
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is 0, the disk will be closed once and for all.
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.El
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Specifying wrong argument values to the above ioctl command will cause
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the driver to return an error condition with
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.Va errno
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set to
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.Er EINVAL .
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Any attempt to perform something else then selecting a quirks record
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on a device where this has not been done yet will return an error of
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.Er ENXIO .
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.Pp
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In addition, the
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.Xr scsi 4
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general ioctls may be used with the
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.Nm
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driver, but only against the control device.
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.Sh BUGS
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The driver is considered beta quality. There's still a lot of
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polishing required.
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.Pp
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Preparing the driver for a CD-R from another vendor will require you
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to understand the source code, be used to the SCSI-2 specification,
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hold a copy of the vendor's SCSI reference manual on your desk, and
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have a lot of patience and CD-R's.
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.Pp
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The driver should include all the functionality of the
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.Xr cd 4
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driver. No strategy for implementing this kind of interaction has
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been designed yet.
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.Pp
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The first
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.Em Unit Attention
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conditition after a media change is often not yet caught, although
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the driver was designed to catch it. This can royally screw a user
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of the driver, thus make sure to manually catch it before actually
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starting a burn. This can be done for example with a dummy
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.Em Test Unit Ready
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command:
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.Bd -literal
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scsi -f /dev/rworm0.ctl -c "0 0 0 0 0 0" >/dev/null 2>&1
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.Ed
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.Sh FILES
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.Bl -tag -width /dev/rworm[0-9].ctl -compact
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.It Pa /dev/rworm[0-9]
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device for ioctl's and to write a CD-R
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.It Pa /dev/rworm[0-9].ctl
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the control device, as being used by
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.Xr scsi 8
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.El
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.Sh DIAGNOSTICS
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See above.
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.Sh SEE ALSO
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.Xr cd 4 ,
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.Xr scsi 4 ,
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.Xr scsi 8 ,
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.Xr wormcontrol 8 ,
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.Xr open 2 ,
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.Xr ioctl 2 ,
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.Xr write 2 ,
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.Xr close 2 .
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.Sh AUTHORS
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The first skeleton for a
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.Nm
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driver has been written by Peter Dufault in May, 1995. The driver has
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then been improved and made actually usable at all by
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.ie t J\(:org Wunsch
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.el Joerg Wunsch
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in January, 1996.
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.Sh HISTORY
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The
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.Nm
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driver appeared in FreeBSD 2.1.
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