On Tue, Jul 27, 2021 at 9:13 AM Chengwen Feng [off-list ref] wrote:

Please change to .svg file.
See grep -ri "Inkscape" doc/guides/contributing/documentation.rst
for guidelines.

+
+ * The DMA controller could have multiple hardware DMA channels (aka. hardware
+   DMA queues), each hardware DMA channel should be represented by a dmadev.
+ * The dmadev could create multiple virtual DMA channels, each virtual DMA
+   channel represents a different transfer context. The DMA operation request
+   must be submitted to the virtual DMA channel. e.g. Application could create
+   virtual DMA channel 0 for memory-to-memory transfer scenario, and create
+   virtual DMA channel 1 for memory-to-device transfer scenario.
+
+
+Device Management
+-----------------
+
+Device Creation
+~~~~~~~~~~~~~~~
+
+Physical DMA controller is discovered during the PCI probe/enumeration of the
+EAL function which is executed at DPDK initialization, based on their PCI
+device identifier, each unique PCI BDF (bus/bridge, device, function). Specific
+physical DMA controller, like other physical devices in DPDK can be listed using
+the EAL command line options.
+
+And then dmadevs are dynamically allocated by rte_dmadev_pmd_allocate() based on
+the number of hardware DMA channels.
+
+
+Device Identification
+~~~~~~~~~~~~~~~~~~~~~
+
+Each DMA device, whether physical or virtual is uniquely designated by two
+identifiers:
+
+- A unique device index used to designate the DMA device in all functions
+  exported by the DMA API.
+
+- A device name used to designate the DMA device in console messages, for
+  administration or debugging purposes.
+
+
+Device Configuration
+~~~~~~~~~~~~~~~~~~~~
+
+The rte_dmadev_configure API is used to configure a DMA device.
+
+.. code-block:: c
+
+   int rte_dmadev_configure(uint16_t dev_id,
+                            const struct rte_dmadev_conf *dev_conf);
+
+The ``rte_dmadev_conf`` structure is used to pass the configuration parameters
+for the DMA device for example maximum number of virtual DMA channels,
+indication of whether to enable silent mode.
+
+
+Configuration of Virtual DMA Channels
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The rte_dmadev_vchan_setup API is used to configure a virtual DMA channel.
+
+.. code-block:: c
+
+   int rte_dmadev_vchan_setup(uint16_t dev_id,
+                                     const struct rte_dmadev_vchan_conf *conf);
+
+The ``rte_dmadev_vchan_conf`` structure is used to pass the configuration
+parameters for the virtual DMA channel for example transfer direction, number of
+descriptor for the virtual DMA channel, source device access port parameter,
+destination device access port parameter.

Looks good. Some other section really useful and it is specific to
DMADEV could be added

1) ring_idx management, You can copy the texts from API header file or so
2) rte_dmadev_completed() management.
3) Talk about silent mode too.