# what's meaning of /dev/led/ahcichX.locate



## Dunpengcheng (Aug 7, 2013)

What's the meaning of the device /dev/led/ahcichX.locate. Is it a disk LED? 

When I use the command `echo f > /dev/led/ahcichX.locate`, or the command 
`echo 0 > /dev/led/ahcichX.locate`, the disk LED status doesn't change at all.

What's the problem and how to operate the disk LEDs?

Thanks all.


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## ondra_knezour (Aug 7, 2013)

It is the LED supposed to signalize given disk position. Another two are the activity and fault signals.

From ahci(4)


> Driver supports "LED" enclosure management messages, defined by the AHCI. When supported by hardware, it allows to control per-port activity, locate and fault LEDs via the led(4) API for localization and status reporting purposes.  Supporting AHCI controllers may transmit that infor mation to the backplane controllers via SGPIO interface. Backplane controllers interpret received statuses in some way (IBPI standard) to report them using present indicators.



Support depends on the controller and connected backplane. For possible signaling see the led(4) manpage.


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## mav@ (Aug 7, 2013)

That functionality is usually present only in server boards in the form of SGPIO connectors on the motherboard, that could be connected to the disk backplane, that actually may have LEDs for it. Unfortunately on desktop boards SGPIO connectors are usually missing, and that is impossible to detect by software.


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