参照元†
- const dma_cap_mask_t *mask
- dma_filter_fn fn
- void *fn_param
返り値†
CONFIG_DMA_ENGINE 無効: include/linux/dmaengine.h†
static inline struct dma_chan *__dma_request_channel(const dma_cap_mask_t *mask,
dma_filter_fn fn, void *fn_param)
{
return NULL;
}
CONFIG_DMA_ENGINE 有効: drivers/dma/dmaengine.c†
/**
* __dma_request_channel - try to allocate an exclusive channel
* @mask: capabilities that the channel must satisfy
* @fn: optional callback to disposition available channels
* @fn_param: opaque parameter to pass to dma_filter_fn
*
* Returns pointer to appropriate DMA channel on success or NULL.
*/
struct dma_chan *__dma_request_channel(const dma_cap_mask_t *mask,
dma_filter_fn fn, void *fn_param)
{
struct dma_device *device, *_d;
struct dma_chan *chan = NULL;
int err;
/* Find a channel */
mutex_lock(&dma_list_mutex);
list_for_each_entry_safe(device, _d, &dma_device_list, global_node) {
chan = private_candidate(mask, device, fn, fn_param);
if (chan) {
/* Found a suitable channel, try to grab, prep, and
* return it. We first set DMA_PRIVATE to disable
* balance_ref_count as this channel will not be
* published in the general-purpose allocator
*/
dma_cap_set(DMA_PRIVATE, device->cap_mask);
device->privatecnt++;
err = dma_chan_get(chan);
if (err == -ENODEV) {
pr_debug("%s: %s module removed\n",
__func__, dma_chan_name(chan));
list_del_rcu(&device->global_node);
} else if (err)
pr_debug("%s: failed to get %s: (%d)\n",
__func__, dma_chan_name(chan), err);
else
break;
if (--device->privatecnt == 0)
dma_cap_clear(DMA_PRIVATE, device->cap_mask);
chan = NULL;
}
}
mutex_unlock(&dma_list_mutex);
pr_debug("%s: %s (%s)\n",
__func__,
chan ? "success" : "fail",
chan ? dma_chan_name(chan) : NULL);
return chan;
}
EXPORT_SYMBOL_GPL(__dma_request_channel);
コメント†