This patch adds dmadev library guide. Signed-off-by: Chengwen Feng <fengcheng...@huawei.com> --- doc/guides/prog_guide/dmadev.rst | 126 +++++++++++++++ doc/guides/prog_guide/img/dmadev_i1.svg | 278 ++++++++++++++++++++++++++++++++ doc/guides/prog_guide/index.rst | 1 + 3 files changed, 405 insertions(+) create mode 100644 doc/guides/prog_guide/dmadev.rst create mode 100644 doc/guides/prog_guide/img/dmadev_i1.svg
diff --git a/doc/guides/prog_guide/dmadev.rst b/doc/guides/prog_guide/dmadev.rst new file mode 100644 index 0000000..c6327db --- /dev/null +++ b/doc/guides/prog_guide/dmadev.rst @@ -0,0 +1,126 @@ +.. SPDX-License-Identifier: BSD-3-Clause + Copyright 2021 HiSilicon Limited + +DMA Device Library +==================== + +The DMA library provides a DMA device framework for management and provisioning +of hardware and software DMA poll mode drivers, defining generic APIs which +support a number of different DMA operations. + + +Design Principles +----------------- + +The DMA library follows the same basic principles as those used in DPDK's +Ethernet Device framework and the RegEx framework. The DMA framework provides +a generic DMA device framework which supports both physical (hardware) +and virtual (software) DMA devices as well as a generic DMA API which allows +DMA devices to be managed and configured and supports DMA operations to be +provisioned on DMA poll mode driver. + +.. _figure_dmadev_i1: + +.. figure:: img/dmadev_i1.* + + The model of the DMA framework built on + + * 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. + + +Device Features and Capabilities +-------------------------------- + +DMA devices may support different feature set. In order to get the supported PMD +features ``rte_dmadev_info_get`` API which returns the info of the device and +it's supported features. + +A special device capability is silent mode which application don't required to +invoke dequeue APIs. + + +Enqueue / Dequeue APIs +~~~~~~~~~~~~~~~~~~~~~~ + +The enqueue APIs include like ``rte_dmadev_copy`` and ``rte_dmadev_fill``, if +enqueue successful, an uint16_t ring_idx is returned. This ring_idx can be used +by applications to track per-operation metadata in an application defined +circular ring. + +The ``rte_dmadev_submit`` API was used to issue doorbell to hardware, and also +there are flags (``RTE_DMA_OP_FLAG_SUBMIT``) parameter of the enqueue APIs +could do the same work. + +There are two dequeue APIs (``rte_dmadev_completed`` and +``rte_dmadev_completed_status``) could used to obtain the result of request. +The first API returns the number of operation requests completed successfully, +the second API returns the number of operation requests completed which may +successfully or failed and also with meaningful status code. Also these two +APIs could return the last completed operation's ring_idx which will help to +track application-defined circular ring. diff --git a/doc/guides/prog_guide/img/dmadev_i1.svg b/doc/guides/prog_guide/img/dmadev_i1.svg new file mode 100644 index 0000000..b305beb --- /dev/null +++ b/doc/guides/prog_guide/img/dmadev_i1.svg @@ -0,0 +1,278 @@ +<?xml version="1.0" encoding="UTF-8" standalone="no"?> +<!-- Created with Inkscape (http://www.inkscape.org/) --> + +<svg + width="206.19344mm" + height="168.97479mm" + viewBox="0 0 206.19344 168.97479" + version="1.1" + id="svg934" + inkscape:version="1.1 (c68e22c387, 2021-05-23)" + sodipodi:docname="dmadev_i1.svg" + xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"; + xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"; + xmlns="http://www.w3.org/2000/svg"; + xmlns:svg="http://www.w3.org/2000/svg";> + <sodipodi:namedview + id="namedview936" + pagecolor="#ffffff" + bordercolor="#666666" + borderopacity="1.0" + 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