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 <redacted>
Cc: Alexey Malahov <redacted>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: linux-mips@vger.kernel.org
Cc: devicetree@vger.kernel.org

---

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;
 }
 EXPORT_SYMBOL_GPL(dma_get_slave_caps);

diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index 6801200c76b6..429eef3a702b 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);

-- 
2.26.2