diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c index 9e56745f87bf..5932ab164ace 100644 --- a/drivers/dma/dmaengine.c +++ b/drivers/dma/dmaengine.c @@ -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 diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h index cb286b1acdb6..c271608e862e 100644 --- a/include/linux/dmaengine.h +++ b/include/linux/dmaengine.h @@ -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) \