93 lines
1.8 KiB
Text
93 lines
1.8 KiB
Text
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.TH INTRO 3
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.SH NAME
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intro \- introduction to the Plan 9 devices
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.SH DESCRIPTION
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A Plan 9
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.I device
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implements a file tree for client processes.
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A file name beginning with a pound sign, such as
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.LR #c ,
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names the root of a file tree implemented by
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a particular
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.IR "kernel device driver"
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identified by the character after the pound sign.
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Such names are usually bound to conventional locations
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in the name space.
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For example, after
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.IP
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.EX
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bind("#c", "/dev", MREPL)
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.EE
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.LP
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an
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.IR ls (1)
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of
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.B /dev
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will list the files provided by the
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.I console
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device.
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.PP
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A kernel device driver is a
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.I server
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in the sense of the Plan 9 File Protocol, 9P (see Section 5),
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but with the messages implemented by local
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rather than remote procedure calls.
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Also, several of the messages
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.RI ( Nop ,
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.IR Session ,
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.IR Flush ,
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and
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.IR Error )
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have no subroutine equivalents.
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.PP
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When a system call is passed a file name beginning with
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.L "#"
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it looks at the next character, and if that is a valid
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.I device character
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it performs an
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.IR attach (5)
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on the corresponding device to get a channel representing the
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root of that device's file tree.
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If there are any characters after the device character but
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before the next
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.L "/"
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or end of string, those characters are passed as parameter
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.I aname
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to the attach. For example,
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.IP
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.EX
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#I2
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.EE
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.PP
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identifies the number 2 IP protocol stack
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(see
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.IR ip (3)).
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.PP
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Each kernel device has a conventional place at which to be bound
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to the name space.
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The
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.I SYNOPSIS
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sections of the following pages includes a
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.I bind
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command to put the device in the conventional place.
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Most of these binds are done automatically by
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.IR init (8)
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using
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.B newns
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(see
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.IR auth (2))
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on the file
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.B /lib/namespace
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(see
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.IR namespace (6)).
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When typed to
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.IR rc (1),
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the
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.I bind
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commands will need quotes to protect the
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.B #
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characters.
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.SH SEE ALSO
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.IR intro (5),
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.IR intro (2)
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