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.Dd March 2, 1996 .Dt LEDS 4 sun2 .Os .Sh NAME .Nm leds .Nd sun2 diagnostic Light Emitting Diodes driver .Sh SYNOPSIS n machine/leds.h .Sh DESCRIPTION All sun2 machines are equipped a diagnostic display of eight Light Emitting Diodes (LEDs), located on either the front (deskside chassis) or the back (desktop machine) of the system unit.
p The kernel changes the display during periods of idle processor activity according to a stored sequential pattern list. The
a /dev/leds interface provides a way of manipulating the pattern list via simple file I/O.
p The structure of the file is as follows: d -literal struct led_patterns { u_char divisor; u_char patlen; u_char pat[256]; }; .Ed l -tag -width divisor t Sy divisor The number of idle periods to wait before switching to the next pattern in the array. t Sy patlen The number of patterns stored in the array. t Sy pat The array of patterns to display. .El
p When a clock interrupt occurs while the processor is idle, a pattern countdown timer is decremented. When the countdown timer reaches zero it is reset with the .Sy divisor value and the next pattern in the array is selected and displayed.
p Each 8-bit pattern describes the state of the diagnostic LEDs. A set bit in a pattern indicates that its corresponding LED should be extinguished, while a reset bit indicates an LED to be illuminated. .Sh FILES l -tag -width /dev/leds -compact t Pa /dev/leds .El .Sh EXAMPLES The following example uses .Xr awk 1 to display the repeating animation of a single lit LED scrolling from one end of the display to the other, using six clock ticks between each update. d -ragged -offset indent # echo 5 8 254 253 251 247 239 223 191 127 | awk '{ for (i=1;i<=NF;i++) printf("%c",$i+0); }' > /dev/leds .Ed .Sh ERRORS An I/O transfer to
a /dev/leds will complete successfully unless: l -tag -width Er t Bq Er EIO A read or write starting beyond the end of the file was attempted. .El .Sh SEE ALSO .Xr ppt 6 .Sh HISTORY
Indexes created Mon Sep 22 05:09:51 GMT 2025