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
---
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 03ac4b96117c..6baddf7dcbfd 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -1302,6 +1302,79 @@ 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_GPL(dmaengine_desc_attach_metadata);
+
+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);
+}
+EXPORT_SYMBOL_GPL(dmaengine_desc_get_metadata_ptr);
+
+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);
+}
+EXPORT_SYMBOL_GPL(dmaengine_desc_set_metadata_len);
+
/* dma_wait_for_async_tx - spin wait for a transaction to complete
* @tx: in-flight transaction to wait on
*/
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index 8fcdee1c0cf9..40d062c3b359 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -219,6 +219,58 @@ 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 / DEV_MEM_TO_MEM:
+ * 1. prepare the descriptor (dmaengine_prep_*)
+ * construct the metadata in the client's buffer
+ * 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_
