Charging USB devices with Fedora

[Ambrogio]

Hi all,

I had 2 different MP3 player that require USB connection to recharging
it.

My problem is that I can't be able to charge them.
USB Connection is good, I can transfer data from and to the devices but
battery doesn't charge.

Searching on the web I found something about USB drivers required, or
about some echo to be done on special files.
I can't be able to done the job.

I have two Laptop, one with fedora 10 and one with fedora 12, even if I
think problem isn't on the version of O.S.

There is someone that can help me solving the question?

Bye
 Ambrogio