On Thursday 17 May 2007, David Brownell wrote: > On Thursday 17 May 2007, Laurent Pinchart wrote: > > On Wednesday 16 May 2007, David Brownell wrote: > > > On Wednesday 16 May 2007, Hans Petter Selasky wrote: > > > > in that when you have > > > > pre-allocated all buffers and all USB host controller descriptors, > > > > you will never get in the situation of not being able to allocate > > > > transfer descriptors on the fly, like done on Linux. > > > > > > That's not a failure mode that's been often observed on Linux. (Never, > > > in my own experience... which I admit has not focussed on that > > > particular type of stress load.) So it's hard to argue that it should > > > motivate a redesign of core APIs. > > > > A user of the Linux UVC driver unfortunately reported such a failure. The > > driver allocates 5 bulk URBs, and the device asked for a 2.7MB buffer. > > Buffer != transfer descriptor.
Ok, sorry for the noise. > The bug here is asking for a 2.7 MB block of contiguous memory. > As previously discussed, that's not necessary ... or desirable. > Drivers asking for such things are buggy -- except possibly on > dedicated systems. I'm testing a driver patch to allocate much smaller buffers. I will probably run into issues with buggy devices that send a zero packet when the actual payload size is equal to the maximum payload size, and is a multiple of the packet size, but that's another story. Laurent Pinchart ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
