diff mbox series

[v7,1/6] dmaengine: Add API function dmaengine_prep_peripheral_dma_vec()

Message ID 20240223-iio-dmabuf-v7-1-78cfaad117b9@analog.com (mailing list archive)
State Superseded
Headers show
Series iio: new DMABUF based API | expand

Commit Message

Nuno Sa Feb. 23, 2024, 12:13 p.m. UTC 
From: Paul Cercueil <paul@crapouillou.net>

This function can be used to initiate a scatter-gather DMA transfer,
where the address and size of each segment is located in one entry of
the dma_vec array.

The major difference with dmaengine_prep_slave_sg() is that it supports
specifying the lengths of each DMA transfer; as trying to override the
length of the transfer with dmaengine_prep_slave_sg() is a very tedious
process. The introduction of a new API function is also justified by the
fact that scatterlists are on their way out.

Note that dmaengine_prep_interleaved_dma() is not helpful either in that
case, as it assumes that the address of each segment will be higher than
the one of the previous segment, which we just cannot guarantee in case
of a scatter-gather transfer.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Nuno Sa <nuno.sa@analog.com>
---
 include/linux/dmaengine.h | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

Comments

Nuno Sá March 4, 2024, 11:10 a.m. UTC | #1 
On Fri, 2024-02-23 at 13:13 +0100, Nuno Sa wrote:
> From: Paul Cercueil <paul@crapouillou.net>
> 
> This function can be used to initiate a scatter-gather DMA transfer,
> where the address and size of each segment is located in one entry of
> the dma_vec array.
> 
> The major difference with dmaengine_prep_slave_sg() is that it supports
> specifying the lengths of each DMA transfer; as trying to override the
> length of the transfer with dmaengine_prep_slave_sg() is a very tedious
> process. The introduction of a new API function is also justified by the
> fact that scatterlists are on their way out.
> 
> Note that dmaengine_prep_interleaved_dma() is not helpful either in that
> case, as it assumes that the address of each segment will be higher than
> the one of the previous segment, which we just cannot guarantee in case
> of a scatter-gather transfer.
> 
> Signed-off-by: Paul Cercueil <paul@crapouillou.net>
> Signed-off-by: Nuno Sa <nuno.sa@analog.com>
> ---

Hi Vinod,

Is this already good for you? I do not want to be pushy but we're trying to see
if we can have this in the 6.9 cycle and Jonathan definitely wants an ack from
you before merging this in his tree. I've more or less till Wednesday so that's
why I'm asking already today so I still have time to re-spin if you want some
changes.

- Nuno Sá
diff mbox series

Patch

diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index 752dbde4cec1..856df8cd9a4e 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -160,6 +160,16 @@  struct dma_interleaved_template {
 	struct data_chunk sgl[];
 };
 
+/**
+ * struct dma_vec - DMA vector
+ * @addr: Bus address of the start of the vector
+ * @len: Length in bytes of the DMA vector
+ */
+struct dma_vec {
+	dma_addr_t addr;
+	size_t len;
+};
+
 /**
  * enum dma_ctrl_flags - DMA flags to augment operation preparation,
  *  control completion, and communicate status.
@@ -910,6 +920,10 @@  struct dma_device {
 	struct dma_async_tx_descriptor *(*device_prep_dma_interrupt)(
 		struct dma_chan *chan, unsigned long flags);
 
+	struct dma_async_tx_descriptor *(*device_prep_peripheral_dma_vec)(
+		struct dma_chan *chan, const struct dma_vec *vecs,
+		size_t nents, enum dma_transfer_direction direction,
+		unsigned long prep_flags, unsigned long flags);
 	struct dma_async_tx_descriptor *(*device_prep_slave_sg)(
 		struct dma_chan *chan, struct scatterlist *sgl,
 		unsigned int sg_len, enum dma_transfer_direction direction,
@@ -973,6 +987,19 @@  static inline struct dma_async_tx_descriptor *dmaengine_prep_slave_single(
 						  dir, flags, NULL);
 }
 
+static inline struct dma_async_tx_descriptor *dmaengine_prep_peripheral_dma_vec(
+	struct dma_chan *chan, const struct dma_vec *vecs, size_t nents,
+	enum dma_transfer_direction dir, unsigned long prep_flags,
+	unsigned long flags)
+{
+	if (!chan || !chan->device || !chan->device->device_prep_peripheral_dma_vec)
+		return NULL;
+
+	return chan->device->device_prep_peripheral_dma_vec(chan, vecs, nents,
+							    dir, prep_flags,
+							    flags);
+}
+
 static inline struct dma_async_tx_descriptor *dmaengine_prep_slave_sg(
 	struct dma_chan *chan, struct scatterlist *sgl,	unsigned int sg_len,
 	enum dma_transfer_direction dir, unsigned long flags)