245 lines
5.1 KiB
Text
245 lines
5.1 KiB
Text
.TH USBD 4
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.SH NAME
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usbd \- Universal Serial Bus daemon
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.SH SYNOPSIS
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.B usbd
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[
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.B -Dd
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]
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[
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.B -s
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.I srv
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]
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[
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.B -m
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.I mnt
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]
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[
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.I hub...
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]
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.SH DESCRIPTION
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.I Usbd
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complements
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.IR usb (3)
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to provide USB I/O for device drivers.
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It enumerates the bus, polling
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hub ports to detect device attachments and detachments, performs
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initial configuration of setup endpoints, and writes extra information into
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.IR usb (3)
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endpoint control files, to ease device location.
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.PP
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By default,
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.I usbd
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opens all setup endpoints found at
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.B #u/usb
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(which correspond to built-in hubs initialized by the kernel during boot).
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Paths to directories representing setup endpoints for hubs can be given
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as arguments to restrict
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.I usbd
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operation to such hubs.
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.PP
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When a device is attached,
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depending upon a configuration file compiled into
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.I usbd ,
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the appropriate device driver may be started without
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user intervention.
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This mechanism can be used to statically link some USB device drivers into
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.I usbd
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itself.
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Initial configuration for setup endpoints is performed independently
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of this configuration.
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.PP
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.I Usbd
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provides a file interface used to change debugging flags, and also used by
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USB device drivers statically linked into
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.IR usbd .
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By default, the file system is mounted (after) at
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.B /dev
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and a 9P connection is posted at
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.BR /srv/usb .
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.PP
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Besides files provided by device drivers, the file
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.B usbdctl
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is always present in the file interface.
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It accepts these control requests:
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.TF "fsdebug\fI n
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.TP
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.BI debug " n"
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Sets the debugging level to
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.IR n .
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.TP
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.BI fsdebug " n"
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Sets the file system debugging level to
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.IR n .
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.TP
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.B dump
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Prints the list of devices and file systems known by
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.IR usbd .
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.PD
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.PP
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.I Usbd
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recognizes the following options:
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.TF "-m\fI mnt
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.TP
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.B -d
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Print debugging diagnostics.
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Repeating the option increases verbosity.
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.TP
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.B -D
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Print debugging diagnostics for the file system interface.
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.TP
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.BI -m " mnt"
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Mount the served file system at
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.IR mnt .
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.TP
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.BI -s " srv"
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Post a 9P connection at
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.BI #s/ srv.
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.PD
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.SS Configuration
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.PP
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.I Usbd
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can be configured to start drivers for devices matching one or more CSPs
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(hex representation of USB class, subclass and protocol), class,
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subclass, protocol, vendor id, or device id.
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When a new device is attached,
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.I usbd
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scans the configuration and, if an entry matches the device descriptor, starts
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the driver.
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If no driver is configured, the setup endpoint for the device is left
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configured to let the user start the driver by hand.
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.PP
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Configuration is via compilation
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because one of the options is to embed (link) the driver into the
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.I usbd
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binary.
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If the driver is embedded,
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.I usbd
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creates a process for it and calls its main entry point.
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Otherwise,
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.I usbd
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tries to locate the driver binary in
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.B /bin/usb
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and creates a process to execute it.
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.PP
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The configuration file,
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.BR usbdb ,
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has two sections:
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.B embed
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and
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.BR auto .
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Each section includes lines to configure particular drivers.
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A driver may have more than one line if necessary.
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Each line includes the name of the
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driver (the base name of the binary) and one or more attributes of the form
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.IP
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.IR name = value
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.PP
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The following attributes exist:
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.TF subclass
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.TP
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.B class
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.I Value
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may be the name of the class
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or a number identifying the device class (using C syntax).
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The following class names are known:
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.BR audio ,
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.BR comms ,
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.BR hid ,
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.BR printer ,
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.BR storage ,
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.BR hub ,
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and
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.BR data .
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.TP
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.B subclass
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.I Value
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is the number of the device subclass.
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.TP
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.B proto
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.I Value
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is the number of the device protocol.
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.TP
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.B csp
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.I Value
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is the hexadecimal number describing the CSP for the device.
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.TP
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.B vid
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.I Value
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is the vendor id.
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.TP
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.B did
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.I Value
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is the device id.
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.TP
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.B args
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This must be the last field.
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The value is the rest of the line,
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and is supplied as arguments to the driver process.
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.PD
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.LP
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Several environment variables can be used to alter the behaviour of
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.IR usbd ,
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for example, for use in
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.IR plan9.ini (8).
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.B usbdebug
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sets a debug level (zero for no diagnostics and positive
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values for increasing verbosity).
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.B kbargs
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overrides the keyboard arguments as specified by the configuration file.
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.B diskargs
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overrides the disk arguments in the same way.
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.SH EXAMPLE
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This configuration file links
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.B usb/kb
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into
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.I usbd
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when it is compiled.
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It arranges for the driver's entry point,
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.B kbmain
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in this case,
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to be called for any device with CSPs matching either
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.B 0x010103
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or
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.BR 0x020103 .
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Option
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.B -d
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will be supplied as command line arguments for
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.BR kbmain .
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This configuration also arranges for
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.B /bin/usb/disk
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to start (with no arguments) whenever a device of class
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.B storage
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is attached.
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.IP
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.EX
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embed
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kb csp=0x010103 csp=0x020103 args=-d
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auto
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disk class=storage args=
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.EE
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.SH FILES
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.TF /srv/usb
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.TP
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.B /srv/usb
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9P connection to the driver file system.
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.TP
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.B /dev
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mount point for the driver file system.
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.TP
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.B /sys/src/cmd/usb/usbd/usbdb
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Configuration file deciding which devices are included into
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.I usbd
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and which ones are started automatically.
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.SH SOURCE
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.B /sys/src/cmd/usb/usbd
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.SH "SEE ALSO"
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.IR usb (2),
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.IR usb (3),
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.IR usb (4)
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.SH BUGS
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.I Usbd
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is not supposed to be restarted.
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This is arguable.
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.PP
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Not heavily exercised yet.
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