I know that the OK LED can be accessed from /sys/class/leds/led0, but the FDX and 100 are not. I can see from /sys/class/net/eth0/duplex and /sys/class/net/eth0/speed that the files seem to correspond with the leds. I can not write to /sys/class/net/eth0/speed or duplex, even as superuser. Is it possible to write to the file from a kernel module? I am on Arch.

1 Answer 1


Although the LAN9512 datasheet says that the pins used to drive the speed and duplex LEDs can be used for GPIO as far as I can tell there is no support in the linux kernel module to actually switch the pins on the LAN9512 into GPIO mode.

  • I am looking to control the FDX, 100, and LNK LEDs from C/C++. According to raspberrypi.org/phpBB3//viewtopic.php?p=136266#p136266, they are hardwired to the Ethernet chip.
    – built1n
    Aug 20, 2013 at 22:38
  • Right the ethernet chip is the LAN9512, it is also a USB hub. I could not even find any clear information about how to use those pins for GPIO in the LAN9512 documentation, only that that they could be used as GPIO pins.
    – Craig
    Aug 21, 2013 at 16:02

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