On Fri, 14 Nov 2008 14:34:53 -0700, Dan Williams [off-list ref] wrote:

To ensure that all channels are not consumed by the general-purpose
allocator the DMA_PRIVATE capability is provided to exclude a dma_device
from general-purpose (memory-to-memory) consideration.

...

+			/* Found a suitable channel, try to grab, prep, and
+			 * return it.  We first set DMA_PRIVATE to disable
+			 * balance_ref_count as this channel will not be
+			 * published in the general-purpose allocator
+			 */
+			dma_cap_set(DMA_PRIVATE, device->cap_mask);
+			err = dma_chan_get(chan);

The dma_request_channel() set DMA_PRIVATE but dma_release_channel()
does not clear it.

If a client (such as dmatest) grabbed a public channel by
dma_request_channel(), the channel will stay private forever.

While a dma driver might set DMA_PRIVATE initially for private-only
channels, dma_release_channel() cannot clear it unconditionally.

How can this solved?  DMA_ALWAYS_PRIVATE or device->is_private or
something will needed?

---
Atsushi Nemoto