From: Paul Cercueil <paul@crapouillou.net>
To: Vinod Koul <vkoul@kernel.org>
Cc: "Jonathan Cameron" <jic23@kernel.org>,
"Jonathan Corbet" <corbet@lwn.net>,
"Lars-Peter Clausen" <lars@metafoo.de>,
"Sumit Semwal" <sumit.semwal@linaro.org>,
"Christian König" <christian.koenig@amd.com>,
"Daniel Vetter" <daniel@ffwll.ch>, "Nuno Sa" <nuno.sa@analog.com>,
"Michael Hennerich" <Michael.Hennerich@analog.com>,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
dmaengine@vger.kernel.org, linux-iio@vger.kernel.org,
linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org,
linaro-mm-sig@lists.linaro.org
Subject: Re: [PATCH v6 1/6] dmaengine: Add API function dmaengine_prep_slave_dma_vec()
Date: Tue, 30 Jan 2024 18:23:31 +0100 [thread overview]
Message-ID: <fcf3e49cae178b18c0b15e12c69f9f2a84e8312e.camel@crapouillou.net> (raw)
In-Reply-To: <ZbkfC31eWBUQ3kSl@matsya>
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 <paul@crapouillou.net>
> >
> > ---
> > 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
>
next prev parent reply other threads:[~2024-01-30 17:23 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-29 17:01 [PATCH v6 0/6] iio: new DMABUF based API, v6 Paul Cercueil
2024-01-29 17:01 ` [PATCH v6 1/6] dmaengine: Add API function dmaengine_prep_slave_dma_vec() Paul Cercueil
2024-01-30 16:08 ` Vinod Koul
2024-01-30 17:23 ` Paul Cercueil [this message]
2024-01-29 17:01 ` [PATCH v6 2/6] dmaengine: dma-axi-dmac: Implement device_prep_slave_dma_vec Paul Cercueil
2024-01-29 17:01 ` [PATCH v6 3/6] iio: core: Add new DMABUF interface infrastructure Paul Cercueil
2024-01-29 17:01 ` [PATCH v6 4/6] iio: buffer-dma: Enable support for DMABUFs Paul Cercueil
2024-01-29 17:02 ` [PATCH v6 5/6] iio: buffer-dmaengine: Support new DMABUF based userspace API Paul Cercueil
2024-01-29 17:02 ` [PATCH v6 6/6] Documentation: iio: Document high-speed DMABUF based API Paul Cercueil
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