Re: New USB stack on FreeBSD w/Linux emulation layer coming
David Brownell <[email protected]>
| Newsgroups | gmane.linux.usb.devel |
|---|---|
| Message-ID | <[email protected]> |
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. 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. - Dave > The > system had been used for quite some time, and the user reported that > allocating such an amount of contiguous memory made the box swap out and > become very slow. > > 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/ _______________________________________________ [email protected] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel