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authorStephen Warren <swarren@nvidia.com>2013-11-26 21:04:22 +0400
committerVinod Koul <vinod.koul@intel.com>2013-12-10 16:16:48 +0400
commit0ad7c00057dc1640647c1dc81ccbd009de17a767 (patch)
treeb73891fc496ebb59a4fb531667d7f89d58698786 /include/linux/dmaengine.h
parent6ce4eac1f600b34f2f7f58f9cd8f0503d79e42ae (diff)
downloadlinux-0ad7c00057dc1640647c1dc81ccbd009de17a767.tar.xz
dma: add channel request API that supports deferred probe
dma_request_slave_channel() simply returns NULL whenever DMA channel lookup fails. Lookup could fail for two distinct reasons: a) No DMA specification exists for the channel name. This includes situations where no DMA specifications exist at all, or other general lookup problems. b) A DMA specification does exist, yet the driver for that channel is not yet registered. Case (b) should trigger deferred probe in client drivers. However, since they have no way to differentiate the two situations, it cannot. Implement new function dma_request_slave_channel_reason(), which performs identically to dma_request_slave_channel(), except that it returns an error-pointer rather than NULL, which allows callers to detect when deferred probe should occur. Eventually, all drivers should be converted to this new API, the old API removed, and the new API renamed to the more desirable name. This patch doesn't convert the existing API and all drivers in one go, since some drivers call dma_request_slave_channel() then dma_request_channel() if that fails. That would require either modifying dma_request_channel() in the same way, or adding extra error-handling code to all affected drivers, and there are close to 100 drivers using the other API, rather than just the 15-20 or so that use dma_request_slave_channel(), which might be tenable in a single patch. acpi_dma_request_slave_chan_by_name() doesn't currently implement deferred probe. It should, but this will be addressed later. Acked-by: Dan Williams <dan.j.williams@intel.com> Signed-off-by: Stephen Warren <swarren@nvidia.com> Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Diffstat (limited to 'include/linux/dmaengine.h')
-rw-r--r--include/linux/dmaengine.h8
1 files changed, 8 insertions, 0 deletions
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index 41cf0c399288..ed92b30a02fd 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -22,6 +22,7 @@
#define LINUX_DMAENGINE_H
#include <linux/device.h>
+#include <linux/err.h>
#include <linux/uio.h>
#include <linux/bug.h>
#include <linux/scatterlist.h>
@@ -1040,6 +1041,8 @@ enum dma_status dma_wait_for_async_tx(struct dma_async_tx_descriptor *tx);
void dma_issue_pending_all(void);
struct dma_chan *__dma_request_channel(const dma_cap_mask_t *mask,
dma_filter_fn fn, void *fn_param);
+struct dma_chan *dma_request_slave_channel_reason(struct device *dev,
+ const char *name);
struct dma_chan *dma_request_slave_channel(struct device *dev, const char *name);
void dma_release_channel(struct dma_chan *chan);
#else
@@ -1063,6 +1066,11 @@ static inline struct dma_chan *__dma_request_channel(const dma_cap_mask_t *mask,
{
return NULL;
}
+static inline struct dma_chan *dma_request_slave_channel_reason(
+ struct device *dev, const char *name)
+{
+ return ERR_PTR(-ENODEV);
+}
static inline struct dma_chan *dma_request_slave_channel(struct device *dev,
const char *name)
{