Man page for der Mouse and Gordon Ross's /dev/leds diagnostic LED interface.
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.\" $NetBSD: leds.4,v 1.1 1997/05/21 01:40:03 jeremy Exp $
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.\"
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.\" Copyright (c) 1997 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by der Mouse and Jeremy Cooper.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the NetBSD
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.\" Foundation, Inc. and its contributors.
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.\" 4. Neither the name of The NetBSD Foundation nor the names of its
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.\" contributors may be used to endorse or promote products derived
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.\" from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd March 2, 1996
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.Dt LEDS 4 sun3
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.Os NetBSD 1.1a
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.Sh NAME
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.Nm leds
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.Nd sun3 diagnostic LED(s)
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.Sh SYNOPSIS
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.nf
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.ft B
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#include <machine/leds.h>
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.ft R
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.fi
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.Sh DESCRIPTION
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With the exception of the 3/80, all sun3 machines are equipped a diagnostic
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display of eight Light Emitting Diodes,
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located on the back of the system unit.
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The 3/80 has a single LED, which is located on the front panel.
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.Pp
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The kernel changes the display during periods of idle processor activity
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according to a stored sequential pattern list.
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The
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.Nm /dev/leds
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interface provides a way of manipulating the pattern list via simple file I/O.
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.Pp
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The structure of the file is as follows:
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.Bd -literal
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struct led_patterns {
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u_char divisor;
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u_char patlen;
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u_char pat[256];
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};
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.Ed
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.Bl -tag -width divisor
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.It Sy divisor
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The number of idle periods to wait before switching to the next pattern in
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the array.
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.It Sy patlen
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The number of patterns stored in the array.
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.It Sy pat
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The array of patterns to display.
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.El
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.Pp
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When a clock interrupt occurs while the processor is idle, a pattern
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countdown timer is decremented. When the countdown timer reaches zero
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it is reset with the
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.Sy divisor
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value and the next pattern in the array is selected and displayed.
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.Pp
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Each 8-bit pattern describes the state of the diagnostic LEDs.
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With the exception of the 3/80, a set bit in a pattern indicates that its
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corresponding LED should be be extinguished,
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while a reset bit indicates an LED to be illuminated.
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On the 3/80 the polarity of the bits is reversed and only the lowest order bit
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is used.
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.Sh EXAMPLES
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The following example uses
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.Xr awk 1
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to display the repeating animation of a single lit LED scrolling from one end
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of the display to the other, using six clock ticks between each update.
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.Bd -ragged -offset -ident
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# echo 5 8 254 253 250 247 239 223 191 127 |
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awk '{ for (i=1;i<=NF;i++) printf("%c",$i+0); }' > /dev/leds
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.Ed
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.Sh "ERRORS"
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An I/O transfer to
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.Nm /dev/leds
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will complete successfully unless:
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.Bl -tag -width Er
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.It Bq Er EIO
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A read or write starting beyond the end of the file was attempted.
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.El
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.Sh FILES
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.Bl -tag -width /dev/leds -compact
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.It Pa /dev/leds
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.El
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.Sh "SEE ALSO"
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.Xr ppt 6
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.Sh HISTORY
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.Nm /dev/leds
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appeared in post-1.1 NetBSD.
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