Usb Power Budget, Is powering usb peripherals unsafe? Options

[Armagon]

I'm running OZ on my C1000, but I think this is a fairly general question.


In kernel 2.16 and newer, if a USB device requires too much power, it is not enabled. 'dmesg' output might look like:

usb 1-2: no configuration chosen from 1 choice

To find out how much power a USB device wants, one can invoke:

lsusb -v | grep MaxPower

My card reader wants up to 250 mA, and my USB to serial converter says it might use up to 500 mA!

Post #3 on this ubuntu forum thread describes a work-around.

So my question is, is it safe to do this? [Also, I assume that people who are using kernels before 2.16 could well ask the same question, even if the device isn't automatically disabled.] Are the manufacturers of these USB products giving a high margin of error? Can a high-current device damage a Zaurus, or will it simply shorten battery life or just plain not work?

Thank you,
Armagon

[Edit]. PS. Does it make any difference if the Z is plugged in or not?

[speculatrix]

the guy who put usb wifi and bluetooth inside a C1000 found he could increase the power available to the usb port using a resistor... the risk is as much from heating and/or burning a track on the PCB as anything else.

personally, I'd use a battery-powered hub (hmmm, really, you just need one with rechargeable battery or ultracapacitor than recharges from usb bus, so it will handle peaks of current?). I see figlabs have a nice usb external hard drive which is rechargeable, and probably ideal for many people.

on the subject of external hard drives, I note that Asus (used to) do a usb/wifi hard drive which runs samba... ideal to put in the car, sync your MP3's to it when you get home, and stream audio from it using your Z!