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.TH SD 3

.SH NAME

sd \- storage device interface

.SH SYNOPSIS

.nf

.B bind #S /dev

.sp 0.4v

.B /dev/sdctl

.BI /dev/sd Cu /ctl

.BI /dev/sd Cu /raw

.BI /dev/sd Cu /data

\&...

.fi

.SH DESCRIPTION

The storage device interface serves a two-level directory

giving access to multiple storage units,

typically ATA(PI) or SCSI discs.

Each unit

is accessed via files in the directory named by the controller

to which it is attached,

.IR C  ,

and by its unit number

.IR u .

The controller naming convention for ATA(PI) units starts

with the first controller being named

.LR C ,

the second

.LR D ,

etc. up to a maximum of 4 controllers

.RB ([ C-F ]);

legacy controllers are always 'C' and 'D'.

There can be a maximum of 2 units per ATA(PI) controller

.RB ([ 01 ]).

The controller naming convention for SCSI units starts with

the first controller being named

.LR 0 ,

the second

.LR 1 ,

etc. up to a maximum of 16 controllers

.RB ([ 0-9a-f ]).

There can be a maximum of 16 units per SCSI controller

.RB ([ 0-9a-f ]).

.PP

Units are not accessed before the first attach.

Units may be individually attached using the attach specifier,

for example

.IP

.EX

bind -a '#SsdD0' /dev

.EE

.PP

An attach without a specifier will cause the driver to scan for all possible

units before processing the rest of the name.

.PP

The subdirectory for each unit contains two files,

.I ctl

and

.IR raw .

In addition,

if the unit is a direct-access disc of some type

it may be split into partitions and

the subdirectory may contain a file per partition.

By default,

the partition

.I data

will exist for such media.

.SS "\fIctl\fP and partitions

Partitions are added and deleted by writing to the

.I ctl

file

.IP

.EX

part \f2name start-sector end-sector\fP

delpart \f2name\fP

.EE

.PP

The default

.I data

partition may be deleted.

A partition cannot be deleted if a process has it open.

If a change of removable media is detected,

the new media cannot be opened until all open partitions

on the old media are closed.

.PP

Partitions are usually created using

.I fdisk

and

.IR prep (8);

the convention is to name non-Plan 9 partitions after their corresponding operating systems

(e.g.,

.BR /dev/sdC0/dos )

and Plan 9 partitions according to their function

(e.g.,

.BR /dev/sdC0/swap ).

The example in

.IR prep (8)

shows how.

.PP

Reading the

.I ctl

file returns at least one line of textual information about

the unit.

The first line will always be prefixed by

.L inquiry

and will give a manufacturer and model number if possible.

A line prefixed by

.L config

will be returned for appropriate media,

e.g. for ATA(PI) units the remainder of the line contains

configuration information from the device's

.I identify

command (config and capabilities)

and also the available I/O transfer options;

this is a diagnostic aid.

A line prefixed by

.L geometry

will be returned for appropriate media;

at least two numbers will follow,

the first being the number of sectors contained in the unit

and the second the sector size in bytes.

Any remaining information on the

.B geometry

line is unit-dependent,

for instance, head,

cylinder and sector counts for ATA discs.

If any partitions are defined for the media,

their name, start-sector and end-sector will be returned,

prefixed by

.LR part .

.IP

.EX

% cat /dev/sdD0/ctl

inquiry KENWOOD CD-ROM UCR-421  208E10/20/99  7.39  2 M0

config 85C0 capabilities 0F00 dma 00550004 dmactl 00000000

geometry 242725 2352

part data 0 242725

%

.EE

.PP

The use of DMA and multi-sector read/write commands may be

enabled and disabled on ATA(PI) units by writing to the

.B ctl

file

.B dma

and

.B rwm

respectively followed by

.B on

or

.BR off .

For example, to enable DMA on a unit that supports it:

.IP

.EX

% echo 'dma on'>/dev/sd00/ctl

.EE

.PP

If supported by the unit,

the standby timer may be enabled:

.IP

.EX

% echo 'standby \f2T\fP'>/dev/sdC0/ctl

.EE

.PP

where

.I T

is the standby timer period in seconds.

.I T

must be between 30 and 1200,

or can be 0 to disable the timer.

.SS \fIraw\fP

The

.I raw

file is used to execute an arbitrary command on the unit at

a low level.

This is used by programs such as

.IR scuzz (8)

to manipulate devices that do not fit the simple storage model

or for maintenance purposes.

The following steps may be taken to execute a command

.IP \- 3

Write the command to the

.I raw

file;

.IP \-

Read or write data associated with the command, according to the direction of the transfer.

.IP \-

Read the

.I raw

file to retrieve the status of the command,

returned as a text integer.

.SS sdctl

Reading

.B /dev/sdctl

yields information about each controller,

one line per controller.

Writing `\fLconfig\fI message\fR' to

.B /dev/sdctl

passes

.I message

to the legacy configuration machinery,

used to set attributes such as IRQ, port and size.

Writing `\fIctltype message\fR' to

.B /dev/sdctl

passes

.I message

to

.IR ctltype 's

.B wtopctl

function with a nil

.B sdev

argument,

where

.I ctltype

is a known controller type such as

.B ata

or

.BR scsi .

Writing `\c

.BI sd "ctlletter message\fR'

to

.B /dev/sdctl

passes

.I message

to

.BI sd ctlletter\fR's

.B wtopctl

function with an

.B sdev

argument corresponding to the named controller,

where

.I ctlletter

is a known controller letter such as

.B C

or

.BR 0 .

.SH SOURCE

.B /sys/src/9/port/devsd.c

.br

.B /sys/src/9/*/sd*.[hc]

.SH SEE ALSO

.IR scuzz (8)

.SH BUGS

LUNs (logical unit numbers) are not implemented.

For (S)ATA drives,

LUNs are not merely ignored but are actively

prevented from working except for INQUIRY commands.

.PP

The 4 controller limit for ATA(PI) is not enforced.

.PP

No account is taken of some buggy ATA PCI controllers

such as the CMD640.

.PP

ATA(PI) units come up with DMA and multi-sector read/write

capability disabled.