From 7bb587f4eef8f71ce589f360ab99bb54ab0fc85d Mon Sep 17 00:00:00 2001 From: Zhangfei Gao Date: Fri, 28 Jun 2013 20:39:12 +0800 Subject: [PATCH] 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 Acked-by: Arnd Bergmann Signed-off-by: Vinod Koul --- drivers/dma/dmaengine.c | 26 ++++++++++++++++++++++++++ include/linux/dmaengine.h | 1 + 2 files changed, 27 insertions(+) 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) \ -- 2.45.2