title: Read/Write same MTLTexture on iOS
body: <p>The <code>texture2d</code> <code>access::read_write</code> qualifier seems only available on OSX. Is there a way to read/write the same texture inside a <code>kernel</code> (or other) metal function?</p>
  
  <p>The reason is the written texture values may not be final and can be updated by other threads.</p>