On Thu, Feb 09, 2023 at 09:33:06AM +0000, JiaJie Ho wrote: > > Why do you copy everything before you feed it to the hardware? > > If the issue is alignment then surely you should only to copy a small amount > > of header (and perhaps trailer) for that? > > > > The DMA can only support 32-bit addressing. > So, I am copying everything in case kernel allocated memory region >32-bit for a user app. The DMA API takes care of that.