On Fri, 19 Mar 2010, Gadiyar, Anand wrote: > > I have been working on map_urb_for_dma() and unmap_urb_for_dma(), and > > it seems like a good idea to EXPORT the unmap routine so that HCDs > > could call it when they need to revert to PIO. And of course, we will > > also need to add changes for drivers that have to use PIO for control > > transfers but can use DMA for other transfer types. > > > > For this problem, two approaches were suggested: > > Either we need to add fine grained description of the DMA requirements > or these exceptional drivers need to handle DMA issues on their own. > > We started off with the first approach, and then after the second > one was suggested, we started looking at that (did not want to > disturb other hcd drivers just because MUSB has a problem). Not sure > which approach is better. A requirement like "This driver can use DMA except for control transfers" is okay; that can be implemented simply enough in usbcore. Anything more complicated probably should be handled directly in the driver. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
