1.\" $NetBSD: leds.4,v 1.14 2022/08/28 10:48:16 hgutch Exp $ 2.\" 3.\" Copyright (c) 1997 The NetBSD Foundation, Inc. 4.\" All rights reserved. 5.\" 6.\" This code is derived from software contributed to The NetBSD Foundation 7.\" by der Mouse and Jeremy Cooper. 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 19.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 20.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 21.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 22.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 23.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 24.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 25.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 26.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 27.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 28.\" POSSIBILITY OF SUCH DAMAGE. 29.\" 30.Dd March 2, 1996 31.Dt LEDS 4 sun3 32.Os 33.Sh NAME 34.Nm leds 35.Nd sun3 diagnostic Light Emitting Diodes driver 36.Sh SYNOPSIS 37.In machine/leds.h 38.Sh DESCRIPTION 39With the exception of the Sun 3/80, all sun3 machines are equipped 40a diagnostic display of eight Light Emitting Diodes (LEDs), located 41on the back of the system unit. 42The Sun 3/80 has a single LED, which is located on the front panel. 43.Pp 44The kernel changes the display during periods of idle processor activity 45according to a stored sequential pattern list. 46The 47.Pa /dev/leds 48interface provides a way of manipulating the pattern list via simple file I/O. 49.Pp 50The structure of the file is as follows: 51.Bd -literal 52struct led_patterns { 53 u_char divisor; 54 u_char patlen; 55 u_char pat[256]; 56}; 57.Ed 58.Bl -tag -width divisor 59.It Sy divisor 60The number of idle periods to wait before switching to the next pattern in 61the array. 62.It Sy patlen 63The number of patterns stored in the array. 64.It Sy pat 65The array of patterns to display. 66.El 67.Pp 68When a clock interrupt occurs while the processor is idle, a pattern 69countdown timer is decremented. 70When the countdown timer reaches zero 71it is reset with the 72.Sy divisor 73value and the next pattern in the array is selected and displayed. 74.Pp 75Each 8-bit pattern describes the state of the diagnostic LEDs. 76With the exception of the 3/80, a set bit in a pattern indicates that its 77corresponding LED should be extinguished, 78while a reset bit indicates an LED to be illuminated. 79On the 3/80 the polarity of the bits is reversed and only the lowest order bit 80is used. 81.Sh FILES 82.Bl -tag -width /dev/leds -compact 83.It Pa /dev/leds 84.El 85.Sh EXAMPLES 86The following example uses 87.Xr awk 1 88to display the repeating animation of a single lit LED scrolling from one end 89of the display to the other, using six clock ticks between each update. 90.Bd -ragged -offset indent 91# echo 5 8 254 253 251 247 239 223 191 127 | 92 awk '{ for (i=1;i<=NF;i++) printf("%c",$i+0); }' > /dev/leds 93.Ed 94.Sh ERRORS 95An I/O transfer to 96.Pa /dev/leds 97will complete successfully unless: 98.Bl -tag -width Er 99.It Bq Er EIO 100A read or write starting beyond the end of the file was attempted. 101.El 102.Sh SEE ALSO 103.Xr ppt 6 104.Sh HISTORY 105.Pa /dev/leds 106first appeared in 107.Nx 1.2 . 108