Returns: 1 if successful and 0 if not
+u64
+dma_get_required_mask(struct device *dev)
+
+After setting the mask with dma_set_mask(), this API returns the
+actual mask (within that already set) that the platform actually
+requires to operate efficiently. Usually this means the returned mask
+is the minimum required to cover all of memory. Examining the
+required mask gives drivers with variable descriptor sizes the
+opportunity to use smaller descriptors as necessary.
+
+Requesting the required mask does not alter the current mask. If you
+wish to take advantage of it, you should issue another dma_set_mask()
+call to lower the mask again.
+
Part Id - Streaming DMA mappings
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