On Sat, 20 Aug 2011, Felipe Balbi wrote: > On Sat, Aug 20, 2011 at 12:33:01AM +0200, Michal Nazarewicz wrote: > > From: Michal Nazarewicz <mina86@xxxxxxxxxx> > > > > This commit renames the “speed” field of the usb_gadget_driver > > structure to “max_speed”. This is so that to make it more > > apparent that the field represents the maximum speed gadget > > driver can support. > > > > This also make the field look more like fields with the same > > name in usb_gadget and usb_composite_driver structures. All > > of those represent the *maximal* speed given entity supports. > > > > After this commit, there are the following fields in various > > structures: > > * usb_gadget::speed - the current connection speed, > > * usb_gadget::max_speed - maximal speed UDC supports, > > this will be handled inside the UDC itself, so why do you need to expose > it ? I wondered about this too. It turns out that sometimes the gadget driver really does need to know about the maximum speed supported by the UDC hardware and driver. For example, suppose the gadget driver and the UDC both support high speed, but the gadget is currently plugged into a USB-1.1 controller and therefore running only at full speed. Then the gadget driver has to respond to the Get-Device-Qualifier and Get-Other-Speed-Config requests by sending the appropriate descriptors. But if the UDC doesn't support high speed operation then the gadget driver has to respond to those requests with a STALL. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
