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dmaengine: introduce dma_request_channel and private channels

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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>
This commit is contained in:
Dan Williams
2009-01-06 11:38:15 -07:00
parent f67b459992
commit 59b5ec2144
2 changed files with 155 additions and 16 deletions
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16
include/linux/dmaengine.h
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@ -89,6 +89,7 @@ enum dma_transaction_type {
DMA_MEMSET,
DMA_MEMCPY_CRC32C,
DMA_INTERRUPT,
DMA_PRIVATE,
DMA_SLAVE,
};
@ -223,6 +224,18 @@ struct dma_client;
typedef enum dma_state_client (*dma_event_callback) (struct dma_client *client,
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
@ -472,6 +485,9 @@ void dma_async_device_unregister(struct dma_device *device);
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 --- */