Comment Re:Mod summary up! (Score 1) 482
A cell phone isn't going to source power to anything. My PDA isn't going to source power to anything[...]
You don't anticipate them supplying power to the USB peripherals (memory sticks) you plug into them?
[...] My computer isn't going to source power to anything (via the charging jack). [...]
It would be a nice feature if it could, so you could feed one device from another's battery (I do that a lot charging my phone from my laptop when travelling), but I agree it almost certainly won't happen - at least not with the standard under discussion, which is complex and yet not sophisticated in the way USB
Yes, a full-blown USB connection needs to have a smart communication system so the devices can tell the host what they are and etc. No, a device built to charge through a USB connection doesn't need to communicate shit, all it needs to do is see 5V on the input and assume that it is connected to something that will limit the current it will provide if necessary. That means you can use any 5V supply to charge it, whether that is a laptop, a battery, or a wind turbine.
I often charge my cell phone from my laptop, as the phone charges over USB. The phone can also be a USB master. For reasons of bad implementation this phone can't power USB peripherals so you have to use a stupid power+USB splicing cable, but this should change if.when they make a phone that gets it right. That'd be a device charging over USB that needs to negotiate power direction.