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Subject[PATCH v4 05/11] dmaengine: Introduce DMA-device device_caps callback
There are DMA devices (like ours version of Synopsys DW DMAC) which have
DMA capabilities non-uniformly redistributed amongst the device channels.
In order to provide a way of exposing the channel-specific parameters to
the DMA engine consumers, we introduce a new DMA-device callback. In case
if provided it gets called from the dma_get_slave_caps() method and is
able to override the generic DMA-device capabilities.

Signed-off-by: Serge Semin <>
Cc: Alexey Malahov <>
Cc: Thomas Bogendoerfer <>
Cc: Arnd Bergmann <>
Cc: Andy Shevchenko <>
Cc: Rob Herring <>


Changelog v3:
- This is a new patch created as a result of the discussion with Vinod and
Andy in the framework of DW DMA burst and LLP capabilities.
drivers/dma/dmaengine.c | 3 +++
include/linux/dmaengine.h | 2 ++
2 files changed, 5 insertions(+)

diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index ad56ad58932c..edbb11d56cde 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -599,6 +599,9 @@ int dma_get_slave_caps(struct dma_chan *chan, struct dma_slave_caps *caps)
caps->cmd_resume = !!device->device_resume;
caps->cmd_terminate = !!device->device_terminate_all;

+ if (device->device_caps)
+ device->device_caps(chan, caps);
return 0;
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index a7e4d8dfdd19..b303e59929e5 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -899,6 +899,8 @@ struct dma_device {
struct dma_chan *chan, dma_addr_t dst, u64 data,
unsigned long flags);

+ void (*device_caps)(struct dma_chan *chan,
+ struct dma_slave_caps *caps);
int (*device_config)(struct dma_chan *chan,
struct dma_slave_config *config);
int (*device_pause)(struct dma_chan *chan);
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