The USB descriptors reported by lsusb -v will also report the MaxPower value of
a given device.
e.g. my Logitech keyboard is currently reporting a MaxPower usage of 98mA while
my Roccat mouse is reporting 500mA
# lsusb -vd 046d:c53d |grep MaxPower
MaxPower 98mA
# lsusb -vd 1e7d:2dcd |grep MaxPower
MaxPower 500mA
This might be useful if you need to identify at what point USB power draw
becomes a problem.
-Ben
On Tuesday, January 23rd, 2024 at 10:10 AM, Tomas Kuchta
<tomas.kuchta.li...@gmail.com> wrote:
> This article may tell you more about what you need
>
> https://www.baeldung.com/linux/control-usb-power-supply
>
> -T
>
> On Tue, Jan 23, 2024, 12:35 Tomas Kuchta tomas.kuchta.li...@gmail.com
>
> wrote:
>
> > echo 1 > /sys/bus/usb/drivers/usb/bind
> >
> > Will bind it again. The side effect of unbind+bind is usb bus/device
> > reset, depending on whether you are addressing bus or device
> >
> > The number(s) being echoed means:
> > usbBusNo usbPort usbDevice
> > Check the bus/device format in /sys or dmsg or ....
> >
> > There is old article from GKH about how this worked in 2.6 kernels ages
> > ago. It has changed somewhat and improved - see usb kernel sub-system
> > documentation or google for more details.
> >
> > https://lwn.net/Articles/143397/
> >
> > I am typing this on my cell, using google and memory - I was not able to
> > verify current format on my system at home and I use remote multi-user
> > centOS at work (cannot mess with that)
> >
> > Good luck, -T
> >
> > On Tue, Jan 23, 2024, 11:24 Vince Winter thine.technoc...@gmail.com
> > wrote:
> >
> > > It is also about the power draw on the processor power and the system
> > > power
> > > from having a USB controller working. Having any USB plugged adds
> > > noticeable amount of power.
> > >
> > > I am hoping that telling the kernel, as per the suggestions here, to
> > > unpower it that the controller goes back to "sleep mode". Also it would be
> > > convenient if can I bring the device backup with out unplugging it.
> > >
> > > When I have a moment at work, I will get some empirical data if this works
> > > or not.
> > >
> > > On Tue, Jan 23, 2024, 5:51 AM Tomas Kuchta tomas.kuchta.li...@gmail.com
> > > wrote:
> > >
> > > > On Tue, Jan 23, 2024, 01:00 Ted Mittelstaedt t...@portlandia-it.com
> > > > wrote:
> > > >
> > > > > I've messed with this before trying to troubleshoot USB cams.
> > > > >
> > > > > It's highly dependent on the USB hardware. Not all USB devices
> > > > > implement
> > > > > "low power" mode.
> > > > >
> > > > > Your best shot is to get a good USB 4 port hub - not a crappy one - a
> > > > > good
> > > > > one and the good ones
> > > > > Implement power control and can cut power to a USB device if you
> > > > > command
> > > > > them to.
> > > > > .
> > > >
> > > > This is not about how the USB devices (mis)behave. They would not be
> > > > trying
> > > > to control the devices, but the USB host(s) in the PC/laptop, I presume.
> > > >
> > > > USB host can, and will cut power to the bus when directed.
> > > >
> > > > While I am as guilty as any man - the world really sucks when people who
> > > > think they understand stuff speak with undoubted authority about stuff.
> > > >
> > > > Hole it helps, -T
