[9fans] problem with usbd (hub.c) and qemu

[Lonnie Mendez <lmendez19@austin.rr.com>]

   I had a go with qemu, plan9, and usb again.  This time it's 
progressing much farther except another wall has been hit.  usbstart got 
things going up to a certain point.  Running /bin/usb/usbd -d yielded 
this information:

usbd: usb0/0.1: hub 1 attached
pdesc 1.-1 [10]
desc 1.-1 [9] 0x29: nport 8 charac 0x000a pwr 2ms current 0mA remov 0x00
usbd: hub descriptor too small
%

   To me qemu's hub descriptor size calculation is sane.  Looking at

http://cm.bell-labs.com/sources/plan9/sys/src/cmd/usb/usbd/hub.c:newhub()

    pdesc(d, -1, -1, buf, nr);
    dd = (DHub*)buf;
    nport = dd->bNbrPorts;
    nmap = 1 + nport/8;
    if(nr < 7 + 2*nmap) {
        fprint(2, "usbd: hub descriptor too small\n");
        free(h);
        return nil;
    }

   the hub size for a hub with 8+ ports isn't being calculated 
correctly.  In this instance for a hub with 8 ports the code expects 11 
bytes when the hub descriptor size is 10 bytes.  Please see usb_20 
11.23.2.1 or usb11 11.15.2 concerning DeviceRemovable and 
PortPwrCtrlMask.  Source for the qemu hub is located here:

http://cvs.savannah.nongnu.org/viewcvs/qemu/hw/usb-hub.c?rev=1.3&root=qemu&view=markup

   usb_hub_handle_control() - switch case GetHubDescriptor