On 30-08-18, 15:19, Peter Ujfalusi wrote: > The metadata is best described as side band data or parameters traveling > alongside the data DMAd by the DMA engine. It is data > which is understood by the peripheral and the peripheral driver only, the > DMA engine see it only as data block and it is not interpreting it in any > way. > > The metadata can be different per descriptor as it is a parameter for the > data being transferred. > > If the DMA supports per descriptor metadata it can implement the attach, > get_ptr/set_len callbacks. > > Client drivers must only use either attach or get_ptr/set_len to avoid > misconfiguration. > > Client driver can check if a given metadata mode is supported by the > channel during probe time with > dmaengine_is_metadata_mode_supported(chan, DESC_METADATA_CLIENT); > dmaengine_is_metadata_mode_supported(chan, DESC_METADATA_ENGINE); > > and based on this information can use either mode. > > Wrappers are also added for the metadata_ops. > > To be used in DESC_METADATA_CLIENT mode: > dmaengine_desc_attach_metadata() > > To be used in DESC_METADATA_ENGINE mode: > dmaengine_desc_get_metadata_ptr() > dmaengine_desc_set_metadata_len() > > Signed-off-by: Peter Ujfalusi <[email protected]> > --- > drivers/dma/dmaengine.c | 73 ++++++++++++++++++++++++++ > include/linux/dmaengine.h | 108 ++++++++++++++++++++++++++++++++++++++ > 2 files changed, 181 insertions(+) > > diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c > index f1a441ab395d..53bd1eae23f2 100644 > --- a/drivers/dma/dmaengine.c > +++ b/drivers/dma/dmaengine.c > @@ -1306,6 +1306,79 @@ void dma_async_tx_descriptor_init(struct > dma_async_tx_descriptor *tx, > } > EXPORT_SYMBOL(dma_async_tx_descriptor_init); > > +static inline int desc_check_and_set_metadata_mode( > + struct dma_async_tx_descriptor *desc, enum dma_desc_metadata_mode mode) > +{ > + /* Make sure that the metadata mode is not mixed */ > + if (!desc->desc_metadata_mode) { > + if (dmaengine_is_metadata_mode_supported(desc->chan, mode)) > + desc->desc_metadata_mode = mode; > + else > + return -ENOTSUPP; > + } else if (desc->desc_metadata_mode != mode) { > + return -EINVAL; > + } > + > + return 0; > +} > + > +int dmaengine_desc_attach_metadata(struct dma_async_tx_descriptor *desc, > + void *data, size_t len) > +{ > + int ret; > + > + if (!desc) > + return -EINVAL; > + > + ret = desc_check_and_set_metadata_mode(desc, DESC_METADATA_CLIENT); > + if (ret) > + return ret; > + > + if (!desc->metadata_ops || !desc->metadata_ops->attach) > + return -ENOTSUPP; > + > + return desc->metadata_ops->attach(desc, data, len); > +} > +EXPORT_SYMBOL(dmaengine_desc_attach_metadata);
EXPORT_SYMBOL_GPL ? -- ~Vinod
