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 <[email protected]>
---
v3: New patch
v5: Replace with function dmaengine_prep_slave_dma_vec(), and struct
'dma_vec'.
Note that at some point we will need to support cyclic transfers
using dmaengine_prep_slave_dma_vec(). Maybe with a new "flags"
parameter to the function?
---
include/linux/dmaengine.h | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index 3df70d6131c8..ee5931ddb42f 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_slave_dma_vec)(
+ struct dma_chan *chan, const struct dma_vec *vecs,
+ size_t nents, enum dma_transfer_direction direction,
+ 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,
@@ -972,6 +986,17 @@ static inline struct dma_async_tx_descriptor *dmaengine_prep_slave_single(
dir, flags, NULL);
}
+static inline struct dma_async_tx_descriptor *dmaengine_prep_slave_dma_vec(
+ struct dma_chan *chan, const struct dma_vec *vecs, size_t nents,
+ enum dma_transfer_direction dir, unsigned long flags)
+{
+ if (!chan || !chan->device || !chan->device->device_prep_slave_dma_vec)
+ return NULL;
+
+ return chan->device->device_prep_slave_dma_vec(chan, vecs, nents,
+ dir, 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)
--
2.43.0
On 29-01-24, 18:01, Paul Cercueil wrote:
> 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 <[email protected]>
>
> ---
> v3: New patch
>
> v5: Replace with function dmaengine_prep_slave_dma_vec(), and struct
> 'dma_vec'.
> Note that at some point we will need to support cyclic transfers
> using dmaengine_prep_slave_dma_vec(). Maybe with a new "flags"
> parameter to the function?
that would be better
> ---
> include/linux/dmaengine.h | 25 +++++++++++++++++++++++++
> 1 file changed, 25 insertions(+)
>
> diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
> index 3df70d6131c8..ee5931ddb42f 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_slave_dma_vec)(
> + struct dma_chan *chan, const struct dma_vec *vecs,
> + size_t nents, enum dma_transfer_direction direction,
> + unsigned long flags);
s/slave/peripheral
I had requested it a bit while ago as well
> 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,
> @@ -972,6 +986,17 @@ static inline struct dma_async_tx_descriptor *dmaengine_prep_slave_single(
> dir, flags, NULL);
> }
>
> +static inline struct dma_async_tx_descriptor *dmaengine_prep_slave_dma_vec(
> + struct dma_chan *chan, const struct dma_vec *vecs, size_t nents,
> + enum dma_transfer_direction dir, unsigned long flags)
> +{
> + if (!chan || !chan->device || !chan->device->device_prep_slave_dma_vec)
> + return NULL;
> +
> + return chan->device->device_prep_slave_dma_vec(chan, vecs, nents,
> + dir, 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)
> --
> 2.43.0
--
~Vinod
Hi Vinod,
Le mardi 30 janvier 2024 à 21:38 +0530, Vinod Koul a écrit :
> On 29-01-24, 18:01, Paul Cercueil wrote:
> > 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 <[email protected]>
> >
> > ---
> > v3: New patch
> >
> > v5: Replace with function dmaengine_prep_slave_dma_vec(), and
> > struct
> > 'dma_vec'.
> > Note that at some point we will need to support cyclic
> > transfers
> > using dmaengine_prep_slave_dma_vec(). Maybe with a new "flags"
> > parameter to the function?
>
> that would be better
Ok, I think it'd be better that I add a new "flags" parameter now -
even if it means passing 0 until we actually have flags for it.
>
> > ---
> > include/linux/dmaengine.h | 25 +++++++++++++++++++++++++
> > 1 file changed, 25 insertions(+)
> >
> > diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
> > index 3df70d6131c8..ee5931ddb42f 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_slave_dma_vec)(
> > + struct dma_chan *chan, const struct dma_vec *vecs,
> > + size_t nents, enum dma_transfer_direction
> > direction,
> > + unsigned long flags);
>
> s/slave/peripheral
>
> I had requested it a bit while ago as well
You did. Sorry, I forgot about it when working on the v6.
Cheers,
-Paul
> > 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,
> > @@ -972,6 +986,17 @@ static inline struct dma_async_tx_descriptor
> > *dmaengine_prep_slave_single(
> > dir, flags,
> > NULL);
> > }
> >
> > +static inline struct dma_async_tx_descriptor
> > *dmaengine_prep_slave_dma_vec(
> > + struct dma_chan *chan, const struct dma_vec *vecs, size_t
> > nents,
> > + enum dma_transfer_direction dir, unsigned long flags)
> > +{
> > + if (!chan || !chan->device || !chan->device-
> > >device_prep_slave_dma_vec)
> > + return NULL;
> > +
> > + return chan->device->device_prep_slave_dma_vec(chan, vecs,
> > nents,
> > + dir,
> > 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)
> > --
> > 2.43.0
>