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Because the TTY hooks interface was not finished when I imported the MPSAFE TTY layer, I had to disconnect the snp(4) driver. This snp(4) implementation has been sitting in my P4 branch for some time now. Unfortunately it still doesn't use the same error handling as snp(4) (returning codes through FIONREAD), but it should already be usable. I'm committing this to SVN, hoping someone else could polish off its rough edges. It's always better than having a broken driver sitting in the tree.
100 lines
1.8 KiB
Groff
100 lines
1.8 KiB
Groff
.\"
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.\" $FreeBSD$
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.\"
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.Dd November 5, 2008
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.Dt SNP 4
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.Os
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.Sh NAME
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.Nm snp
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.Nd tty snoop interface
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.Sh SYNOPSIS
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.In sys/snoop.h
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.Ft int
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.Fn ioctl fd SNPSTTY &dev
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.Ft int
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.Fn ioctl fd SNPGTTY &dev
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.Ft int
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.Fn ioctl fd FIONREAD &result
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.Sh DESCRIPTION
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.Pa /dev/snp
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is a snoop device which allows users to attach to any tty
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and watch activities on it.
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The kernel must be compiled with
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.Cd "device snp" ,
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or the
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.Nm
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module must be loaded,
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for these devices to be available.
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.Pp
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To associate a given
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.Nm
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device with a tty to be observed, open the
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.Nm
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device and a tty device, and then issue the
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.Dv SNPSTTY
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ioctl on
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.Nm
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device.
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The argument passed to the
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.Xr ioctl 2
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is the address of a variable of type
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.Vt int ,
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holding the file descriptor of a tty device.
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To detach the
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.Nm
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device from a tty use a pointer to a value of
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\-1.
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.Pp
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The
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.Dv SNPGTTY
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ioctl returns information about the current tty attached to
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the open
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.Nm
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device.
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.Pp
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The
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.Dv FIONREAD
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ioctl returns a positive value equal to the number of characters
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in a read buffer.
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Special values defined are:
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.Bl -tag -width ".Dv SNP_TTYCLOSE"
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.It Dv SNP_OFLOW
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device overflow occurred, device detached.
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.It Dv SNP_TTYCLOSE
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tty not attached.
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.It Dv SNP_DETACH
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.Nm
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device has been detached by user or tty device has been closed
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and detached.
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.El
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.Sh SEE ALSO
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.Xr pty 4 ,
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.Xr sio 4 ,
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.Xr kldload 8 ,
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.Xr watch 8
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.Sh HISTORY
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The
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.Nm
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device first appeared in
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.Fx 2.1 .
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In
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.Fx 8.0
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the
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.Nm
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driver was rewritten to work with the replaced TTY subsystem.
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.Sh AUTHORS
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The author of the current implementation is
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.An Ed Schouten Aq ed@FreeBSD.org .
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Previous versions of
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.Nm
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were based on code written by
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.An Ugen J.S. Antsilevich Aq ugen@NetVision.net.il .
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.Sh BUGS
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This version of
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.Nm
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does not return proper error codes when calling
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.Dv FIONREAD .
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It also does not allow
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.Dv SNPSTTY
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to detach itself from the TTY.
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