On Thu, Jun 01, 2006 at 10:58:43AM -0400, Alan Stern wrote: > On Thu, 1 Jun 2006, Andrew Morton wrote: > > > On Thu, 01 Jun 2006 02:18:20 -0700 > > David Liontooth <[EMAIL PROTECTED]> wrote: > > > > > Starting with 2.6.16, some USB devices fail unnecessarily on unpowered > > > hubs. Alan Stern explains, > > > > > > "The idea is that the kernel now keeps track of USB power budgets. When > > > a > > > bus-powered device requires more current than its upstream hub is capable > > > of providing, the kernel will not configure it. > > > > > > Computers' USB ports are capable of providing a full 500 mA, so devices > > > plugged directly into the computer will work okay. However unpowered hubs > > > can provide only 100 mA to each port. Some devices require (or claim they > > > require) more current than that. As a result, they don't get configured > > > when plugged into an unpowered hub." > > > > > > http://www.mail-archive.com/linux-usb-devel@lists.sourceforge.net/msg43480.html > > > > > > This is generating a lot of grief and appears to be unnecessarily > > > strict. Common USB sticks with a MaxPower value just above 100mA, for > > > instance, typically work fine on unpowered hubs supplying 100mA. > > > > > > Is a more user-friendly solution possible? Could the shortfall > > > information be passed to udev, which would allow rules to be written per > > > device? > > I'm not sure whether we create a udev event when a new USB device is > connected.
Yes we do. It's of the class "usb_device" and you can write a single udev rule to override the power test if you really want to. Of course I don't recommend someone doing this, as it is violating the USB power rules, and it is a good thing that we are finally testing for them. thanks, greg k-h ------------------------------------------------------- All the advantages of Linux Managed Hosting--Without the Cost and Risk! Fully trained technicians. The highest number of Red Hat certifications in the hosting industry. Fanatical Support. Click to learn more http://sel.as-us.falkag.net/sel?cmd=lnk&kid=107521&bid=248729&dat=121642 _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
