Dobrica Pavlinušić's Weblog / Blog

For some time, I'm seeing strange messages in powertop with mounted SD card:

A USB device is active 100.0% of the time:
USB device  5-5 : UB6225 (ENE)

Since I'm leaving for OSCON (and will mostly work on eee while there) I wanted to be conservative about my battery usage, so I took a closer look at this problem.

At first, installing autofs seemed like good idea. However, autofs can't run scripts (and I really want to toggle card reader's power) so I took a looked at afuse which seemed nice, but I didn't want to add another layer of indirection (missing timeout feature could be solved by script which sleeps in background).

Than I thought about it a bit more and decided that best solution is probably simplest possible: do a small shell script. I usually know when I want to access files on SD card anyway (otherwise, I couldn't really power off card because I would be using files on it).

#!/bin/sh

dir=/rest

if mount | grep $dir >/dev/null ; then

	umount $dir && sudo sh -c "echo 0 > /proc/acpi/asus/cardr"

	sudo rmmod usb-storage

	sudo dmesg -c

else

	if [ `cat /proc/acpi/asus/cardr` -eq 1 ] ; then

		mount $dir && df $dir

	else

		sudo modprobe usb-storage delay_use=0

		sudo sh -c "echo 1 > /proc/acpi/asus/cardr"

		sudo dmesg -c

		sleep 2

		sudo dmesg -c

		mount $dir && df $dir

	fi

fi

You might want to remove dmesg calls if you don't care about output or don't want this script to mess with your kernel logs.