On Wed, 11 Oct 2006, Iñaky Pérez-González wrote: > On Wednesday 11 October 2006 07:22, Alan Stern wrote: > > On Mon, 9 Oct 2006, Inaky Perez-Gonzalez wrote: > > > > > > > pseudo allocates buffer 'maxp' bytes in size using usb_maxpacket() > > > [?? which gets the max packet size from the interrupt > > > endpoint]. That's maybe not as proper. According to the spec > > > (see below) the amount of data to read for the hub status is > > > (PORTS + 1 + 7) / 8 bytes. > > > > That is the amount of data the hub is _supposed_ to send. Some hubs have > > been known to send more. Using the maxpacket size helps to avoid > > EOVERFLOW errors. > > Huh, so that *is* the reason -- then it'd be a good idea to document > it in the code, so the next guy who goes around it doesn't try to do > the same thing I did.
Agreed, it should be commented. > And on the way there, check that the maxpacketsize is bigger or equal > to (PORTS + 1 + 7) / 8 and flag a warning otherwise. If you like, although until now I've never heard of that failing. > > It's a static array defined near the beginning of drivers/usb/core/hcd.c. > > How about I change the maxpacketsize definition to be (USB_MAXCHILDREN + > 1 + 7) / 8? That way we won't have to worry about it any more (and I doubt > it'll ever go over 255 ... so we don't have to worry about endianess either. > I am guessing you refer to changing the value in the static array, right? Yes, that sounds good. Would you mind adding the "maxpacket" comment as well? Alan Stern ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&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
