Comment 25 for bug 953160

The branch attached works around this by allowing us to scan both usb and sdio for connection events. This covers the, apparently common, case where a media card reader is accessed through the common USB bus rather than via SDIO. I'm still also poking around for some way to stab through the USB layer to discover definitively what is attached (rather than relying on device.vendor and device.model) but I've yet to find any real means to do so.