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dmaengine: add interface of dma_get_slave_channel 

Suggested by Arnd, add dma_get_slave_channel interface
Dma host driver could get specific channel specificied by request line, rather than filter.

host example:
static struct dma_chan *xx_of_dma_simple_xlate(struct of_phandle_args *dma_spec,
		struct of_dma *ofdma)
{
	struct xx_dma_dev *d = ofdma->of_dma_data;
	unsigned int request = dma_spec->args[0];

	if (request > d->dma_requests)
		return NULL;

	return dma_get_slave_channel(&(d->chans[request].vc.chan));
}

probe:
of_dma_controller_register((&op->dev)->of_node, xx_of_dma_simple_xlate, d);

Signed-off-by: Zhangfei Gao <zhangfei.gao@linaro.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
This commit is contained in:
Zhangfei Gao 2013-06-28 20:39:12 +08:00 committed by Vinod Koul
parent c095ba7224
commit 7bb587f4ee
2 changed files with 27 additions and 0 deletions
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26
drivers/dma/dmaengine.c
View File

@ -503,6 +503,32 @@ static struct dma_chan *private_candidate(const dma_cap_mask_t *mask,
return NULL;
}
/**
* dma_request_channel - try to get specific channel exclusively
* @chan: target channel
*/
struct dma_chan *dma_get_slave_channel(struct dma_chan *chan)
{
int err = -EBUSY;
/* lock against __dma_request_channel */
mutex_lock(&dma_list_mutex);
if (chan->client_count == 0)
err = dma_chan_get(chan);
else
chan = NULL;
mutex_unlock(&dma_list_mutex);
if (err)
pr_debug("%s: failed to get %s: (%d)\n",
__func__, dma_chan_name(chan), err);
return chan;
}
EXPORT_SYMBOL_GPL(dma_get_slave_channel);
/**
* dma_request_channel - try to allocate an exclusive channel
* @mask: capabilities that the channel must satisfy

1
include/linux/dmaengine.h
View File

@ -995,6 +995,7 @@ int dma_async_device_register(struct dma_device *device);
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);
struct dma_chan *dma_get_slave_channel(struct dma_chan *chan);
struct dma_chan *net_dma_find_channel(void);
#define dma_request_channel(mask, x, y) __dma_request_channel(&(mask), x, y)
#define dma_request_slave_channel_compat(mask, x, y, dev, name) \