2010/9/1 Martin Fuzzey <mfuzzey@xxxxxxxxx>: >> >> dma_unmap_single is needed for bounce_buffer. >> > Yes and it is still done as before (because urb->transfer_dma is the mapped > version of bounce_buffer in this case), the patch to unmap_urb_for_dma > just copies the > bounce buffer back to the transfer_buffer expected by the driver and kfrees > the bounce buffer. > >>> >> Suppose hcd->driver->dma_align_shift is zero and HC is byte aligned DMA >> enabled, this means DMA is doable between byte aligned memory and HC, >> but this does __not__ mean it is safe to do dma mapping or unmapping between >> CPU and byte aligned memory, which may cause sync issues between memory >> and CPU cache. >> >> So seems the idea behind the patch is not correct, IMHO. >> > if dma_align_shift is zero this patch changes nothing. > If there are the problems you describe they were there before and a > separate issue > to the one this patch addresses IMHO. If I don't understand wrong, the patch is introduced to address such issue and to support unaligned transfer_buffer. thanks, -- Lei Ming -- 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
