On 23-08-18, 16:07, 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 > miss configuration. 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 <peter.ujfalusi@xxxxxx> > --- > Hi, > > Changes since rfc: > - DESC_METADATA_EMBEDDED renamed to DESC_METADATA_ENGINE > - Use flow is added for both CLIENT and ENGINE metadata modes > > Regards, > Peter > > include/linux/dmaengine.h | 144 ++++++++++++++++++++++++++++++++++++++ > 1 file changed, 144 insertions(+) > > diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h > index 3db833a8c542..f809635cfeaa 100644 > --- a/include/linux/dmaengine.h > +++ b/include/linux/dmaengine.h > @@ -231,6 +231,57 @@ typedef struct { DECLARE_BITMAP(bits, DMA_TX_TYPE_END); } dma_cap_mask_t; > * @bytes_transferred: byte counter > */ > > +/** > + * enum dma_desc_metadata_mode - per descriptor metadata mode types supported > + * @DESC_METADATA_CLIENT - the metadata buffer is allocated/provided by the > + * client driver and it is attached (via the dmaengine_desc_attach_metadata() > + * helper) to the descriptor. > + * > + * Client drivers interested to use this mode can follow: > + * - DMA_MEM_TO_DEV: > + * 1. prepare the descriptor (dmaengine_prep_*) > + * construct the metadata in the clinet's buffer typo clinet > + * 2. use dmaengine_desc_attach_metadata() to attach the buffer to the > + * descriptor > + * 3. submit the transfer > + * - DMA_DEV_TO_MEM: > + * 1. prepare the descriptor (dmaengine_prep_*) > + * 2. use dmaengine_desc_attach_metadata() to attach the buffer to the > + * descriptor > + * 3. submit the transfer > + * 4. when the transfer is completed, the metadata should be available in the > + * attached buffer I guess this is good to be moved into Documentation also we dont allow this for memcpy txn? > + * > + * @DESC_METADATA_ENGINE - the metadata buffer is allocated/managed by the DMA > + * driver. The client driver can ask for the pointer, maximum size and the > + * currently used size of the metadata and can directly update or read it. > + * dmaengine_desc_get_metadata_ptr() and dmaengine_desc_set_metadata_len() is > + * provided as helper functions. > + * > + * Client drivers interested to use this mode can follow: > + * - DMA_MEM_TO_DEV: > + * 1. prepare the descriptor (dmaengine_prep_*) > + * 2. use dmaengine_desc_get_metadata_ptr() to get the pointer to the engine's > + * metadata area > + * 3. update the metadata at the pointer > + * 4. use dmaengine_desc_set_metadata_len() to tell the DMA engine the amount > + * of data the client has placed into the metadata buffer > + * 5. submit the transfer > + * - DMA_DEV_TO_MEM: > + * 1. prepare the descriptor (dmaengine_prep_*) > + * 2. submit the transfer > + * 3. on transfer completion, use dmaengine_desc_get_metadata_ptr() to get the > + * pointer to the engine's metadata are > + * 4. Read out the metadate from the pointer > + * > + * Note: the two mode is not compatible and clients must use one mode for a > + * descriptor. > + */ > +enum dma_desc_metadata_mode { > + DESC_METADATA_CLIENT = (1 << 0), > + DESC_METADATA_ENGINE = (1 << 1), BIT(x) > +}; > + > struct dma_chan_percpu { > /* stats */ > unsigned long memcpy_count; > @@ -494,6 +545,18 @@ struct dmaengine_unmap_data { > dma_addr_t addr[0]; > }; > > +struct dma_async_tx_descriptor; > + > +struct dma_descriptor_metadata_ops { > + int (*attach)(struct dma_async_tx_descriptor *desc, void *data, > + size_t len); > + > + void *(*get_ptr)(struct dma_async_tx_descriptor *desc, > + size_t *payload_len, size_t *max_len); > + int (*set_len)(struct dma_async_tx_descriptor *desc, > + size_t payload_len); > +}; > + > /** > * struct dma_async_tx_descriptor - async transaction descriptor > * ---dma generic offload fields--- > @@ -523,6 +586,8 @@ struct dma_async_tx_descriptor { > dma_async_tx_callback_result callback_result; > void *callback_param; > struct dmaengine_unmap_data *unmap; > + enum dma_desc_metadata_mode desc_metadata_mode; > + struct dma_descriptor_metadata_ops *metadata_ops; > #ifdef CONFIG_ASYNC_TX_ENABLE_CHANNEL_SWITCH > struct dma_async_tx_descriptor *next; > struct dma_async_tx_descriptor *parent; > @@ -685,6 +750,7 @@ struct dma_filter { > * @global_node: list_head for global dma_device_list > * @filter: information for device/slave to filter function/param mapping > * @cap_mask: one or more dma_capability flags > + * @desc_metadata_modes: supported metadata modes by the DMA device > * @max_xor: maximum number of xor sources, 0 if no capability > * @max_pq: maximum number of PQ sources and PQ-continue capability > * @copy_align: alignment shift for memcpy operations > @@ -749,6 +815,7 @@ struct dma_device { > struct list_head global_node; > struct dma_filter filter; > dma_cap_mask_t cap_mask; > + enum dma_desc_metadata_mode desc_metadata_modes; > unsigned short max_xor; > unsigned short max_pq; > enum dmaengine_alignment copy_align; > @@ -935,6 +1002,83 @@ static inline struct dma_async_tx_descriptor *dmaengine_prep_dma_memcpy( > len, flags); > } > > +static inline bool dmaengine_is_metadata_mode_supported(struct dma_chan *chan, > + enum dma_desc_metadata_mode mode) > +{ > + return !!(chan->device->desc_metadata_modes & mode); > +} > + > +static inline int _desc_check_and_set_metadata_mode( why does this need to start with _ ? > + 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; > +} > + > +static inline 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); > +} > + > +static inline void *dmaengine_desc_get_metadata_ptr( > + struct dma_async_tx_descriptor *desc, size_t *payload_len, > + size_t *max_len) > +{ > + int ret; > + > + if (!desc) > + return ERR_PTR(-EINVAL); > + > + ret = _desc_check_and_set_metadata_mode(desc, DESC_METADATA_ENGINE); > + if (ret) > + return ERR_PTR(ret); > + > + if (!desc->metadata_ops || !desc->metadata_ops->get_ptr) > + return ERR_PTR(-ENOTSUPP); > + > + return desc->metadata_ops->get_ptr(desc, payload_len, max_len); > +} > + > +static inline int dmaengine_desc_set_metadata_len( > + struct dma_async_tx_descriptor *desc, size_t payload_len) > +{ > + int ret; > + > + if (!desc) > + return -EINVAL; > + > + ret = _desc_check_and_set_metadata_mode(desc, DESC_METADATA_ENGINE); > + if (ret) > + return ret; > + > + if (!desc->metadata_ops || !desc->metadata_ops->set_len) > + return -ENOTSUPP; > + > + return desc->metadata_ops->set_len(desc, payload_len); > +} thats bit too much code for a header file :( Lets move it to C file please. We can utilize local dmaengine.h and not expose all these and possible misuse by clients Also I would like to see a use :-) before further comments. -- ~Vinod