On Fri, 29 Jun 2007, Oliver Neukum wrote: > Hi, > > this proved harder than it looks like. I can use cdc-acm over ohci with > this patch. So what do you think?
It tries to do an awful lot all at once. A good place to start would be to use separate allocation for the Iso packet structures. This could be a simple standalone change. Have you looked at Marcel's URB-allocation routine? We seem to be growing a whole variety of them at the moment. Maybe some of them can be combined. There's a more fundamental problem with your approach, though. You can't just allocate the TD's, ED's, and whatnot right alongside the URB. These data structures generally have to be located in DMA-consistent memory (or is it "DMA-coherent"? -- I can never remember the distinction). That's why the HCDs use DMA pools for them. Another problem involves conflicts with disable_endpoint. HCDs use that callback to deallocate their endpoint data structures (EDs for OHCI). But if you're allocating space for the ED along with the URB or trying to associate the two of them somehow, you would end up in peculiar circumstances -- like when the endpoint has been disabled and its ED freed, while its URBs are all killed but still allocated and available for use. Do you really want to bind URBs to specific endpoints? There must be places where drivers use a single URB to carry out multiple functions, talking to different endpoints. Certainly usb-storage does that. Perhaps a better approach, if you insist on pre-allocation, would be at the HCD level. There could be an HCD routine that would reserve space sufficient for a certain number of URBs with a certain total transfer length on a specific endpoint. Then that space would be available for any URB a driver wants to submit -- it wouldn't be coupled to a single URB. Alan Stern ------------------------------------------------------------------------- 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
