108 lines
4.3 KiB
ReStructuredText
108 lines
4.3 KiB
ReStructuredText
.. SPDX-License-Identifier: BSD-3-Clause
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Copyright 2018 NXP
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Rawdevice Library
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=================
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Introduction
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------------
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In terms of device flavor (type) support, DPDK currently has ethernet
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(lib_ether), cryptodev (libcryptodev), eventdev (libeventdev) and vdev
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(virtual device) support.
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For a new type of device, for example an accelerator, there are not many
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options except:
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1. create another lib/librte_MySpecialDev, driver/MySpecialDrv and use it
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through Bus/PMD model.
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2. Or, create a vdev and implement necessary custom APIs which are directly
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exposed from driver layer. However this may still require changes in bus code
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in DPDK.
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The DPDK Rawdev library is an abstraction that provides the DPDK framework a
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way to manage such devices in a generic manner without expecting changes to
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library or EAL for each device type. This library provides a generic set of
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operations and APIs for framework and Applications to use, respectively, for
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interfacing with such type of devices.
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Design
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------
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Key factors guiding design of the Rawdevice library:
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1. Following are some generic operations which can be treated as applicable
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to a large subset of device types. None of the operations are mandatory to
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be implemented by a driver. Application should also be design for proper
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handling for unsupported APIs.
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* Device Start/Stop - In some cases, 'reset' might also be required which
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has different semantics than a start-stop-start cycle.
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* Configuration - Device, Queue or any other sub-system configuration
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* I/O - Sending a series of buffers which can enclose any arbitrary data
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* Statistics - Fetch arbitrary device statistics
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* Firmware Management - Firmware load/unload/status
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2. Application API should be able to pass along arbitrary state information
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to/fro device driver. This can be achieved by maintaining context
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information through opaque data or pointers.
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Figure below outlines the layout of the rawdevice library and device vis-a-vis
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other well known device types like eth and crypto:
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.. code-block:: console
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+-----------------------------------------------------------+
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| Application(s) |
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+------------------------------.----------------------------+
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+------------------------------'----------------------------+
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| DPDK Framework (APIs) |
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+--------------|----|-----------------|---------------------+
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/ \ \
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(crypto ops) (eth ops) (rawdev ops) +----+
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/ \ \ |DrvA|
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+-----'---+ +----`----+ +---'-----+ +----+
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| crypto | | ethdev | | raw |
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+--/------+ +---/-----+ +----/----+ +----+
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/\ __/\ / ..........|DrvB|
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/ \ / \ / ../ \ +----+
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+====+ +====+ +====+ +====+ +==/=+ ```Bus Probe
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|DevA| |DevB| |DevC| |DevD| |DevF|
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+====+ +====+ +====+ +====+ +====+
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| | | | |
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``|``````|````````|``````|`````````````````|````````Bus Scan
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(PCI) | (PCI) (PCI) (PCI)
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(BusA)
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* It is assumed above that DrvB is a PCI type driver which registers itself
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with PCI Bus
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* Thereafter, when the PCI scan is done, during probe DrvB would match the
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rawdev DevF ID and take control of device
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* Applications can then continue using the device through rawdev API
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interfaces
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Device Identification
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~~~~~~~~~~~~~~~~~~~~~
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Physical rawdev devices are discovered during the Bus scan executed at DPDK
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initialization, based on their identification and probing with corresponding
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driver. Thus, a generic device needs to have an identifier and a driver
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capable of identifying it through this identifier.
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Virtual devices can be created by two mechanisms, either using the EAL command
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line options or from within the application using an EAL API directly.
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From the command line using the --vdev EAL option
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.. code-block:: console
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--vdev 'rawdev_dev1'
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Our using the rte_vdev_init API within the application code.
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.. code-block:: c
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rte_vdev_init("rawdev_dev1", NULL)
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