Controlling a USB power supply on off with Linux

Question

Is it possible to turn on off power supplies from USB manually with Linux   There s this external USB cooling fan  the kind you use to cool yourself off  not the PC   and it would be nice to be able to control it from the terminal  because I want to position the fan somewhere far away   I suppose this could also be useful for a variety of other things as well  because there s a lot of USB toys out there  Maybe air purifiers  etc   I heard they don t really work though

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PowerTOP from Intel allows you to toggle devices such as usb peripherals in real-time  These are called  tunables    sudo apt install powertop sudo powertop    Tab over to  tunables   Scroll down to your device  Hit enter to toggle power saving mode  Good Bad      Note that Bad means the device is always on  Toggling to Good will turn off the device after the preset inactive saving time  default is 2000ms     See the PowerTOP docs for details on how to make these changes permanent It generates the config scripts for you  pretty much as described by other posters on this thread    NOTE  These scripts do not affect USB pin power  which is always on   These only send the driver protocol to activate and deactivate a device  If you want to control pin power  you could use either a supported smart USB hub  or better yet a microcontroller

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I wanted to do this  and with my USB hardware I couldn t  I wrote a hacky way how to do it here    http   pintant cat 2012 05 12 power-off-usb-device      In a short way  I used a USB relay to open close the VCC of another USB cable

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I have found these solutions that at least work for properly configured Terminus FE 1 1 USB hub chip   1 To turn off power on all USB ports of a hub  you may unbind the hub from kernel using   echo  1-4 4 4   gt   sys bus usb drivers usb unbind   to turn power back on - you may bind it back using  echo  1-4 4 4   gt   sys bus usb drivers usb bind   2 Switching power at each port individually is trickier  I was able to use hubpower to control each port - but it comes with a downside  hubpower first disconnects the usbdevfs wich causes all of the USB devices to disconect from system  at least on ubuntu   usb ioctl ioctl code   USBDEVFS DISCONNECT  rc   ioctl fd  USBDEVFS IOCTL   amp usb ioctl     With this ioctl disabled I was able to switch off individual port power without detaching all devices - but the power goes back on immediately  probably due to kernel seeing an uninitialized device  which causes USB device just to do a  cold restart  which is what I generally wanted to do  My patched hubpower is here

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You could use my tool uhubctl to control USB power per port for compatible USB hubs

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USB 5v power is always on  even when the computer is turned off  on some computers and on some ports   You will probably need to program an Arduino with some sort of switch  and control it via Serial library from USB plugged in to the computer   In other words  a combination of this switch tutorial and this tutorial on communicating via Serial libary to Arduino plugged in via USB

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The reason why folks post questions such as this is due to the dreaded- indeed  EVIL - USB Auto-Suspend  feature    Auto suspend winds-down the power to an  idle  USB device and unless the device s driver supports this feature correctly  the device can become uncontactable   So powering a USB port on off is a symptom  of the problem  not the problem in itself   I ll show you how to GLOBALLY disable auto-suspend  negating the need to manually toggle the USB ports on  amp  off   Short Answer   You do NOT need to edit  autosuspend delay ms  individually  USB autosuspend can be disabled globally and PERSISTENTLY using the following commands   sed -i  s GRUB CMDLINE LINUX DEFAULT    amp usbcore autosuspend -1     etc default grub  update-grub  systemctl reboot   An Ubuntu 18 04 screen-grab follows at the end of the  Long Answer  illustrating how my results were achieved   Long Answer   It s true that the USB Power Management Kernel Documentation states autosuspend is to be deprecated and in in its  place  autosuspend delay ms  used to disable USB autosuspend    In 2 6 38 the  autosuspend  file will be deprecated and replaced by the  autosuspend delay ms  file     HOWEVER my testing reveals that setting usbcore autosuspend -1 in  etc default grub as below can be used as a GLOBAL toggle for USB autosuspend functionality- you do NOT need to edit individual  autosuspend delay ms  files   The same document linked above states a value of  0  is ENABLED and a negative value is DISABLED   power autosuspend delay ms       lt snip gt  0 means to autosuspend     as soon as the device becomes idle  and negative     values mean never to autosuspend   You can write a     number to the file to change the autosuspend     idle-delay time    In the annotated Ubuntu 18 04 screen-grab below illustrating how my results were achieved  and reproducible   please remark the default is  0   enabled  in autosuspend delay ms    Then note that after ONLY setting usbcore autosuspend -1 in Grub  these values are now negative  disabled  after reboot   This will save me the bother of editing individual values and can now script disabling USB autosuspend     Hope this makes disabling USB autosuspend a little easier and more scriptable-

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echo  2-1   sudo tee  sys bus usb drivers usb unbind   works for ubuntu

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I had a problem when connecting my android phone  I couldn t charge my phone because the power switch on and then off      PowerTop let me find this setting and was useful to fix the issue   auto value was causing issue    echo  on    sudo tee  sys bus usb devices 1-1 power control

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Note  The information in this answer is relevant for the older kernels  up to 2 6 32   See tlwhitec s answer for the information on the newer kernels     disable external wake-up  do this only once echo disabled  gt   sys bus usb devices usb1 power wakeup   echo on  gt   sys bus usb devices usb1 power level         turn on echo suspend  gt   sys bus usb devices usb1 power level    turn off    You may need to change usb1 to usb n   Source  Documentation usb power-management txt gz

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According to the docs  there were several changes to the USB power management from kernels 2 6 32  which seem to settle in 2 6 38  Now you ll need to wait for the device to become idle  which is governed by the particular device driver  The driver needs to support it  otherwise the device will never reach this state  Unluckily  now the user has no chance to force this  However  if you re lucky and your device can become idle  then to turn this off you need to   echo  0   gt    sys bus usb devices usbX power autosuspend  echo  auto   gt    sys bus usb devices usbX power level    or  for kernels around 2 6 38 and above   echo  0   gt    sys bus usb devices usbX power autosuspend delay ms  echo  auto   gt    sys bus usb devices usbX power control    This literally means  go suspend at the moment the device becomes idle   So unless your fan is something  intelligent  that can be seen as a device and controlled by a driver  you probably won t have much luck on current kernels

[linux] Controlling a USB power supply (on/off) with Linux

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