Re: [dpdk-dev] [RFC PATCH] dmadev: introduce DMA device library

[Bruce Richardson <bruce.richardson@intel.com>]

On Wed, Jun 16, 2021 at 03:17:51AM +0100, Wang, Haiyue wrote:
> > -----Original Message-----
> > From: dev <dev-bounces@dpdk.org> On Behalf Of Chengwen Feng
> > Sent: Tuesday, June 15, 2021 21:22
> > To: thomas@monjalon.net; Yigit, Ferruh <ferruh.yigit@intel.com>
> > Cc: dev@dpdk.org; nipun.gupta@nxp.com; hemant.agrawal@nxp.com; maxime.coquelin@redhat.com;
> > honnappa.nagarahalli@arm.com; jerinj@marvell.com; david.marchand@redhat.com; Richardson, Bruce
> > <bruce.richardson@intel.com>; jerinjacobk@gmail.com
> > Subject: [dpdk-dev] [RFC PATCH] dmadev: introduce DMA device library
> >
> > This patch introduces 'dmadevice' which is a generic type of DMA
> > device.
> >
> > The APIs of dmadev library exposes some generic operations which can
> > enable configuration and I/O with the DMA devices.
> >
> > Signed-off-by: Chengwen Feng <fengchengwen@huawei.com>
> > ---
> >  lib/dmadev/rte_dmadev.h     | 531 ++++++++++++++++++++++++++++++++++++++++++++
> >  lib/dmadev/rte_dmadev_pmd.h | 384 ++++++++++++++++++++++++++++++++
> >  2 files changed, 915 insertions(+)
> >  create mode 100644 lib/dmadev/rte_dmadev.h
> >  create mode 100644 lib/dmadev/rte_dmadev_pmd.h
> >
> > diff --git a/lib/dmadev/rte_dmadev.h b/lib/dmadev/rte_dmadev.h
> > new file mode 100644
> > index 0000000..ca7c8a8
> > --- /dev/null
> > +++ b/lib/dmadev/rte_dmadev.h
> > @@ -0,0 +1,531 @@
> > +/* SPDX-License-Identifier: BSD-3-Clause
> > + * Copyright 2021 HiSilicon Limited.
> > + */
> > +
> > +#ifndef _RTE_DMADEV_H_
> > +#define _RTE_DMADEV_H_
> > +
> > +/**
> > + * @file rte_dmadev.h
> > + *
> > + * DMA (Direct Memory Access) device APIs.
> > + *
> > + * Defines RTE DMA Device APIs for DMA operations and its provisioning.
> > + */
> > +
> > +#ifdef __cplusplus
> > +extern "C" {
> > +#endif
> > +
> > +#include <rte_common.h>
> > +#include <rte_memory.h>
> > +#include <rte_errno.h>
> > +#include <rte_compat.h>
> > +
> > +/**
> > + * @warning
> > + * @b EXPERIMENTAL: this API may change without prior notice.
> > + *
> > + * Get the total number of DMA devices that have been successfully
> > + * initialised.
> > + *
> > + * @return
> > + *   The total number of usable DMA devices.
> > + */
> > +__rte_experimental
> > +uint16_t
> > +rte_dmadev_count(void);
> > +
> > +/**
> > + * @warning
> > + * @b EXPERIMENTAL: this API may change without prior notice.
> > + *
> > + * Get the device identifier for the named DMA device.
> > + *
> > + * @param name
> > + *   DMA device name to select the DMA device identifier.
> > + *
> > + * @return
> > + *   Returns DMA device identifier on success.
> > + *   - <0: Failure to find named DMA device.
> > + */
> > +__rte_experimental
> > +int
> > +rte_dmadev_get_dev_id(const char *name);
> > +
> 
> Like 'struct rte_pci_device', 'struct rte_vdev_device', and new introduced
> 'struct rte_auxiliary_device', have the "rte_xxx_device" name style,
> How about 'struct rte_dma_device' name ?

One difference is that the pci, vdev and auxiliary devices are all devices
types on a bus, rather than devices in a functional class like ethdev,
rawdev, eventdev. I think what is here is fine for now - if you feel
strongly we can revisit later.