On Mon, Apr 20, 2009 at 11:51:41PM +0200, Martin Fuzzey wrote: > Hi all, > > I'm working on a HCD for the i.MX21 and am having problems with DMA > alignment [my hardware requires DMA buffers to be aligned on a 4 byte > boundary] > > It seems that the usb core calls dma_map_single() from map_urb_for_dma() > but that this only ensures the memory is is a DMAable region, not that > it is correctly aligned. > > Use case is pwc webcam driver which calls usb_control_message() with a > non aligned stack allocated buffer pointer. That's a bug, it should never do that. I thought we fixed all of these instances, what kernel version are you using that still does this? > Does this mean the HCD has to handle this? (I ask because a brief look > at the existing HCDs didn't turn up anything similar). No, it doesn't, we should fix the driver to always submit heap allocated pointers. That should solve your problem, right? thanks, greg k-h -- 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
