linux-kernel - [PATCH 2/5] dmaengine: Add support for custom data mapping

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Date:   Thu, 15 Dec 2016 15:25:52 +0530
From:   Abhishek Sahu <absahu@...eaurora.org>
To:     vinod.koul@...el.com, dan.j.williams@...el.com,
        andy.gross@...aro.org
Cc:     stanimir.varbanov@...aro.org, mcgrof@...e.com,
        okaya@...eaurora.org, pramod.gurav@...aro.org, arnd@...db.de,
        linux-kernel@...r.kernel.org, dmaengine@...r.kernel.org,
        linux-arm-msm@...r.kernel.org,
        Abhishek Sahu <absahu@...eaurora.org>
Subject: [PATCH 2/5] dmaengine: Add support for custom data mapping

The current DMA APIs only support SGL or data in generic format.
The QCA BAM DMA engine data cannot be mapped with already
available APIs due to following reasons.

1. The QCA BAM DMA engine uses custom flags which cannot be
   mapped with generic DMA engine flags.
2. Some peripheral driver like QCA QPIC NAND/LCD requires to
   set specific flags (Like NWD, EOT) for some of the descriptors
   in scatter gather list. The already available mapping APIs take
   flags parameter in API itself and there is no support for
   passing DMA specific flags for each SGL entry.

Now this patch adds the support for making the DMA descriptor from
custom data with new DMA mapping function prep_dma_custom_mapping.
The peripheral driver will pass the custom data in this function and
DMA engine driver will form the descriptor according to its own
logic. In future, this API can be used by any other DMA engine
drivers also which are unable to do DMA mapping with already
available API’s.

Signed-off-by: Abhishek Sahu <absahu@...eaurora.org>
---
 include/linux/dmaengine.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index cc535a4..6324c1f 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -692,6 +692,8 @@ struct dma_filter {
  *	be called after period_len bytes have been transferred.
  * @device_prep_interleaved_dma: Transfer expression in a generic way.
  * @device_prep_dma_imm_data: DMA's 8 byte immediate data to the dst address
+ * @device_prep_dma_custom_mapping: prepares a dma operation from dma driver
+ *	specific custom data
  * @device_config: Pushes a new configuration to a channel, return 0 or an error
  *	code
  * @device_pause: Pauses any transfer happening on a channel. Returns
@@ -783,6 +785,9 @@ struct dma_device {
 	struct dma_async_tx_descriptor *(*device_prep_dma_imm_data)(
 		struct dma_chan *chan, dma_addr_t dst, u64 data,
 		unsigned long flags);
+	struct dma_async_tx_descriptor *(*device_prep_dma_custom_mapping)(
+		struct dma_chan *chan, void *data,
+		unsigned long flags);

 	int (*device_config)(struct dma_chan *chan,
 			     struct dma_slave_config *config);
-- 
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