On Wed, 20 Sep 2017 17:18:09 -0500 Timur Tabi <ti...@codeaurora.org> wrote:
> I have a device that requires I allocated a few buffers for DMA. The > problem is that this device has only one register for the upper 32 > bits of all of the buffers. That is, all of buffers must reside > within the same 4GB block of memory. In order words, > > end = start + size - 1; > if (upper_32_bits(start) != upper_32_bits(end)) > // Oh no, the buffer spans across a 4GB boundary! > > The buffer is typically less than 16KB in size, so we've never seen > it actually span across a 4GB boundary. However, I want to ensure > that it's impossible. I wrote this function that re-tries the > allocation if the first one is invalid, but I suspect that it's too > hackish. Is there a better way? > Allocate a buffer twice as big as what you really need. If the first half doesn't work, the second half will.
