dmaengine: introduce dma_request_channel and private channels
This interface is primarily for device-to-memory clients which need to
search for dma channels with platform-specific characteristics. The
prototype is:
struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
dma_filter_fn filter_fn,
void *filter_param);
When the optional 'filter_fn' parameter is set to NULL
dma_request_channel simply returns the first channel that satisfies the
capability mask. Otherwise, when the mask parameter is insufficient for
specifying the necessary channel, the filter_fn routine can be used to
disposition the available channels in the system. The filter_fn routine
is called once for each free channel in the system. Upon seeing a
suitable channel filter_fn returns DMA_ACK which flags that channel to
be the return value from dma_request_channel. A channel allocated via
this interface is exclusive to the caller, until dma_release_channel()
is called.
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.
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Maciej Sosnowski <maciej.sosnowski@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index 57a43ad..fe40bc0 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -89,6 +89,7 @@
DMA_MEMSET,
DMA_MEMCPY_CRC32C,
DMA_INTERRUPT,
+ DMA_PRIVATE,
DMA_SLAVE,
};
@@ -224,6 +225,18 @@
struct dma_chan *chan, enum dma_state state);
/**
+ * typedef dma_filter_fn - callback filter for dma_request_channel
+ * @chan: channel to be reviewed
+ * @filter_param: opaque parameter passed through dma_request_channel
+ *
+ * When this optional parameter is specified in a call to dma_request_channel a
+ * suitable channel is passed to this routine for further dispositioning before
+ * being returned. Where 'suitable' indicates a non-busy channel that
+ * satisfies the given capability mask.
+ */
+typedef enum dma_state_client (*dma_filter_fn)(struct dma_chan *chan, void *filter_param);
+
+/**
* struct dma_client - info on the entity making use of DMA services
* @event_callback: func ptr to call when something happens
* @cap_mask: only return channels that satisfy the requested capabilities
@@ -472,6 +485,9 @@
void dma_run_dependencies(struct dma_async_tx_descriptor *tx);
struct dma_chan *dma_find_channel(enum dma_transaction_type tx_type);
void dma_issue_pending_all(void);
+#define dma_request_channel(mask, x, y) __dma_request_channel(&(mask), x, y)
+struct dma_chan *__dma_request_channel(dma_cap_mask_t *mask, dma_filter_fn fn, void *fn_param);
+void dma_release_channel(struct dma_chan *chan);
/* --- Helper iov-locking functions --- */