Re: [PATCH] Add usb_setup_{control, bulk, int}_urb helpers
David Brownell <[email protected]>
| Newsgroups | gmane.linux.usb.devel |
|---|---|
| Message-ID | <[email protected]> |
On Monday 02 July 2007, Alan Stern wrote: > On Sun, 1 Jul 2007, David Brownell wrote: > > Almost true... the constraint applies to either DMA_DIRECTION_* value, > > and dma_sync_single_for_cpu()/dma_sync_single_for_device() are standard > > ways to loosen the constraint. > > Yes, with the dma_sync routines you can reduce the window during which > the cache line must be undisturbed. > > However I don't understand the necessity for this with DMA-OUT > transfers. Obviously _writing_ to the buffer during the transfer is > dangerous, but it's not apparent why _reading_ the buffer should be > bad. There could be performance impacts on some systems. And you said "access" originally, not "write" or "read"... "access" allows writing (which is troublesome), but "read" wouldn't. - Dave ------------------------------------------------------------------------- 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