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Specifically, I'd love to know what the valid values of

  • /sys/devices/virtual/backlight/acpi_video0/power/runtime_enabled
  • /sys/devices/virtual/backlight/acpi_video0/power/wakeup

And, where I can find this information? I've always wondered if it was documented somewhere, or if there was an interface into the kernel to query for it.

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The best (readable by mere mortals) document I found on sysfs is this tutorial by Greg Kroah-Hartman, a linux kernel developer: http://www.linuxjournal.com/article/7353. The tutorial shows how to implement a driver using the sysfs interface. I did not find any references to standards or conventions about documenting valid values.

It seems to be so that any driver can implement things the way the developer likes. Finding the valid values for a sysfs entry is then dependend on the documentation given by the developer. Unfortunately there also seems to be no standard place to find the documentation.

You could search the linux source code (for example here: http://lxr.linux.no/+trees). Unfortunately the linux kernel, being programmed in c, is riddled with macros and pointers, so one can not do a simple grep through the source.

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    If true, how disappointing, that these interfaces in the kernel aren't documented for the end user is mighty annoying.
    – Evan Carroll
    May 13, 2011 at 1:39

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