[PLUG] How to make my laptop look like a USB charger?

[Jason Barnett]

Have you tried Scotch Tape?  Place a small bit in the connector to cover the
two center contacts and plug it in.  This is the equivalent of the Power
Only cable.  It sounds like you don't ever use it for data anyway so there
would be little drawback on this.
- Jason

On Thu, Jan 6, 2011 at 6:55 PM, Eric House <eehouse at eehouse.org> wrote:

> > Eric House wrote:
> > > I have a Dell laptop running Ubuntu and a Virgin Mobile "MiFi"
> > > cellular wifi hotspot.  The MiFi is great but for one bug: when you
> > > plug its USB cable into the laptop to charge it stops being a hotspot,
> > > so you have to carry a separate USB wallwart to charge it.
> > >
> > > I'm pretty sure this is unnecessary -- that if I could get my laptop
> > > to pretend to be a mere USB wallwart I could prevent the loss of wifi.
> > > Googling on the subject turns up instructions for fixing this by
> > > disabling USB Mass Storage mode on windows thus:
> > >
> > > # KB823732 explains how you can disable USB device support by changing
> > > # the Start value of
> > > # HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\UsbStor to 4
> > >
> > > The closest I could think to try on GNU/Linux was to prevent the
> > > usb_storage module from loading, but this didn't work.  The MiFi still
> > > shuts down, meaning it's been signalled in some way by the laptop.
> > >
> > > Can anybody suggest how to do this, or where to read or ask for
> > > further information?  I'm happy to hack the drivers if that's what
> > > it's going to take.  It's apparently possible to fix this by removing
> > > the two inner contacts from a USB cable end, but I don't want to carry
> > > a second cable either -- if I can avoid it.
>
> > Eric House
> > Googling on
> >     linux disable mass storage
> > At
> > <
> http://www.linuxquestions.org/questions/linux-newbie-8/how-to-disable-usb-mass-storage-device-usb-drive-in-linux-651262/
> >
> > it says ...
> > "In linux it's even more easily done, by unloading the usb_storage
> module:
> >
> > modprobe -r usb_storage
> >
> > from the command line"
> > ... then it goes on about how to do that permanently, if that is of any
> > interest.
> > Does that help?
>
> No.  That's the first thing I tried.  Another reply suggested
> disabling the core USB module, which I *can* do on my laptop, but that
> doesn't help either.
>
> BTW, the MiFi presents itself as an ISO 9600 FS -- i.e. it looks like
> a CD-ROM to Ubuntu.  I'm not even sure what the point of that is, but
> then I haven't looked at what files are there -- and can't or I'll
> lose the connection over which I'm writing this. :-)
>
> > The inner contacts are the data lines, and the outer contacts are
> > power.  I'm not sure of the data lines even exist on a wall wart.  The
> > USB standard requires that initialization happens within milliseconds
> > of connecting the cable, and some of that has to happen before the
> > computer even knows that it's a USB Mass storage device.  Depending on
> > how the MiFi device responds to this disabling USB Mass Storage might
> > be too late.  Have you confirmed that it actually works in Windows?
>
> No.  That's an excellent question/idea.  Before I chase this much
> further I'll find myself a windows box.
>
> > Modern Linux will typically load this driver automatically as soon as
> > it's detected, and in some cases may be built into the kernel rather
> > than loaded on use.
> >
> > On my ubuntu system the place to prevent loading the driver would be.
> > /etc/modprobe.d/blacklist.conf
>
> I did that, and confirmed with lsusb that it was not being loaded.  If
> I rmmod'd it and did not add it to the blacklist it would get reloaded
> when I connected the USB cable, but with the blacklist mod that was
> prevented.  Wifi still shuts down, though.
>
> Thanks!
>
> --Eric
> --
>
> ******************************************************************************
> * From the desktop of: Eric House, eehouse at eehouse.org
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