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

[Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>]

<snip>

> 
> On Wed, Jun 16, 2021 at 02:14:54PM +0200, David Marchand wrote:
> > On Tue, Jun 15, 2021 at 3:25 PM Chengwen Feng
> <fengchengwen@huawei.com> wrote:
> > > +
> > > +#define RTE_DMADEV_NAME_MAX_LEN        (64)
> > > +/**< @internal Max length of name of DMA PMD */
> > > +
> > > +/** @internal
> > > + * The data structure associated with each DMA device.
> > > + */
> > > +struct rte_dmadev {
> > > +       /**< Device ID for this instance */
> > > +       uint16_t dev_id;
> > > +       /**< Functions exported by PMD */
> > > +       const struct rte_dmadev_ops *dev_ops;
> > > +       /**< Device info. supplied during device initialization */
> > > +       struct rte_device *device;
> > > +       /**< Driver info. supplied by probing */
> > > +       const char *driver_name;
> > > +
> > > +       /**< Device name */
> > > +       char name[RTE_DMADEV_NAME_MAX_LEN]; } __rte_cache_aligned;
> > > +
> >
> > I see no queue/channel notion.
> > How does a rte_dmadev object relate to a physical hw engine?
> >
> One queue, one device.
> When looking to update the ioat driver for 20.11 release when I added the
> idxd part, I considered adding a queue parameter to the API to look like one
> device with multiple queues. However, since each queue acts completely
> independently of each other, there was no benefit to doing so. It's just easier
> to have a single id to identify a device queue.
Does it mean, the queue is multi thread safe? Do we need queues per core to avoid locking?