On Mon, 1 Mar 2010, Albert Herranz wrote: > > If transfer_buffer_length is 0 then do nothing. > > Otherwise if num_sgs > 0 then do nothing. > > Otherwise if URB_NO_TRANSFER_DMA_MAP and transfer_dma > > are both set (this avoids your HCD_NO_COHERENT_MEM > > case) then do nothing. > > > > I see. This case would include the PIO case too (for which dma_handle > is set to all 1s). The test above should be transfer_dma != ~0, not transfer_dma != 0, since ~0 means the DMA address isn't set. In fact I forgot to include the PIO case; it should be handled by changing the remaining tests as follows: Otherwise if hcd->self.uses_dma is set then If this URB doesn't require PIO then call dma_map_single Otherwise if HCD_LOCAL_MEM is set then call hcd_alloc_coherent Otherwise do nothing (PIO case). Currently "this URB doesn't require PIO" is always true, but in the future it won't be. > So this assumes that transfer_dma should be set initially to 0 when > allocating USB buffers for HCD_NO_COHERENT_MEM. No, it should be set to ~0, the same as when buffers are allocated for a PIO-based controller. 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
