254 lines
5.5 KiB
Text
254 lines
5.5 KiB
Text
.TH SD 3
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.SH NAME
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sd \- storage device interface
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.SH SYNOPSIS
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.nf
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.B bind #S /dev
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.B /dev/sdctl
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.BI /dev/sd Cu /ctl
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.BI /dev/sd Cu /raw
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.BI /dev/sd Cu /data
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\&...
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.fi
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.SH DESCRIPTION
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The storage device interface serves a two-level directory
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giving access to multiple storage units,
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typically ATA(PI) or SCSI discs.
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Each unit
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is accessed via files in the directory named by the controller
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to which it is attached,
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.IR C ,
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and by its unit number
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.IR u .
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The controller naming convention for ATA(PI) units starts
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with the first controller being named
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.LR C ,
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the second
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.LR D ,
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etc. up to a maximum of 4 controllers
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.RB ([ C-F ]);
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legacy controllers are always 'C' and 'D'.
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There can be a maximum of 2 units per ATA(PI) controller
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.RB ([ 01 ]).
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The controller naming convention for SCSI units starts with
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the first controller being named
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.LR 0 ,
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the second
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.LR 1 ,
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etc. up to a maximum of 16 controllers
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.RB ([ 0-9a-f ]).
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There can be a maximum of 16 units per SCSI controller
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.RB ([ 0-9a-f ]).
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.PP
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Units are not accessed before the first attach.
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Units may be individually attached using the attach specifier,
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for example
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.IP
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.EX
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bind -a '#SsdD0' /dev
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.EE
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.PP
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An attach without a specifier will cause the driver to scan for all possible
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units before processing the rest of the name.
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.PP
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The subdirectory for each unit contains two files,
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.I ctl
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and
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.IR raw .
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In addition,
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if the unit is a direct-access disc of some type
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it may be split into partitions and
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the subdirectory may contain a file per partition.
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By default,
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the partition
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.I data
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will exist for such media.
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.PP
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Partitions are added and deleted by writing to the
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.I ctl
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file
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.IP
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.EX
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part \f2name start-sector end-sector\fP
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delpart \f2name\fP
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.EE
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.PP
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The default
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.I data
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partition may be deleted.
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A partition cannot be deleted if a process has it open.
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If a change of removable media is detected,
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the new media cannot be opened until all open partitions
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on the old media are closed.
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.PP
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Partitions are usually created using
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.I fdisk
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and
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.IR prep (8);
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the convention is to name non-Plan 9 partitions after their corresponding operating systems
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(e.g.,
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.BR /dev/sdC0/dos )
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and Plan 9 partitions according to their function
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(e.g.,
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.BR /dev/sdC0/swap ).
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The example in
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.IR prep (8)
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shows how this is done.
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.PP
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Reading the
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.I ctl
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file returns at least one line of textual information about
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the unit.
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The first line will always be prefixed by
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.B inquiry
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and will give a manufacturer and model number if possible.
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A line prefixed by
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.B config
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will be returned for appropriate media,
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e.g. for ATA(PI) units the remainder of the line contains
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configuration information from the device's
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.I identify
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command (config and capabilities)
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and also the available I/O transfer options;
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this is a diagnostic aid.
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A line prefixed by
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.B geometry
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will be returned for appropriate media;
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at least two numbers will follow,
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the first being the number of sectors contained in the unit
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and the second the sector size in bytes.
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Any remaining information on the
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.B geometry
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line is unit-dependent,
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for instance, head,
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cylinder and sector counts for ATA discs.
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If any partitions are defined for the media,
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their name, start-sector and end-sector will be returned,
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prefixed by
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.BR part .
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.IP
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.EX
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% cat /dev/sdD0/ctl
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inquiry KENWOOD CD-ROM UCR-421 208E10/20/99 7.39 2 M0
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config 85C0 capabilities 0F00 dma 00550004 dmactl 00000000
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geometry 242725 2352
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part data 0 242725
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%
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.EE
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.PP
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The use of DMA and multi-sector read/write commands may be
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enabled and disabled on ATA(PI) units by writing to the
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.B ctl
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file
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.B dma
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and
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.B rwm
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respectively followed by
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.B on
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or
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.BR off .
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For example, to enable DMA on a unit that supports it:
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.IP
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.EX
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% echo 'dma on'>/dev/sd00/ctl
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.EE
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.PP
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If supported by the unit,
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the standby timer may be enabled:
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.IP
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.EX
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% echo 'standby \f2T\fP'>/dev/sdC0/ctl
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.EE
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.PP
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where
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.I T
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is the standby timer period in seconds.
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.I T
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must be between 30 and 1200,
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or can be 0 to disable the timer.
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.PP
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The
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.B raw
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file is used to execute an arbitrary command on the unit at
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a low level.
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This is used by programs such as
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.IR scuzz (8)
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to manipulate devices that do not fit the simple storage model
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or for maintenance purposes.
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The following steps may be taken to execute a command
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.IP \- 3
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Write the command to the
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.I raw
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file;
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.IP \-
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Read or write data associated with the command, according to the direction of the transfer.
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.IP \-
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Read the
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.I raw
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file to retrieve the status of the command,
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returned as a text integer.
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.LP
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Reading
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.B /dev/sdctl
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yields information about each controller,
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one line per controller.
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Writing `\fLconfig \fImessage\fR' to
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.B /dev/sdctl
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passes
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.I message
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to the legacy configuration machinery,
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used to set attributes such as IRQ, port and size.
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Writing `\fIctltype message\fR' to
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.B /dev/sdctl
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passes
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.I message
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to
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.IR ctltype 's
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.B wtopctl
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function with a nil
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.B sdev
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argument,
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where
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.I ctltype
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is a known controller type such as
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.B ata
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or
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.BR scsi .
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Writing `\c
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.BI sd "ctlletter message\fR'
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to
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.B /dev/sdctl
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passes
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.I message
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to
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.BI sd ctlletter\fR's
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.B wtopctl
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function with an
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.B sdev
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argument corresponding to the named controller,
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where
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.I ctlletter
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is a known controller letter such as
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.B C
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or
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.BR 0 .
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.SH SOURCE
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.B /sys/src/9/port/devsd.c
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.br
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.B /sys/src/9/*/sd*.[hc]
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.SH SEE ALSO
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.IR scuzz (8)
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.SH BUGS
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LUNs (logical unit numbers) are not implemented.
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For (S)ATA drives,
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LUNs are not merely ignored but are actively
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prevented from working except for INQUIRY commands.
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.PP
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The 4 controller limit for ATA(PI) is not enforced.
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.PP
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No account is taken of some buggy ATA PCI controllers
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such as the CMD640.
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.PP
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ATA(PI) units come up with DMA and multi-sector read/write
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capability disabled.
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