Re: [dpdk-dev] [PATCH] gpudev: introduce memory API

[Thomas Monjalon <thomas@monjalon.net>]

08/06/2021 06:10, Jerin Jacob:
> On Mon, Jun 7, 2021 at 10:17 PM Thomas Monjalon <thomas@monjalon.net> wrote:
> >
> > 07/06/2021 15:54, Jerin Jacob:
> > > On Mon, Jun 7, 2021 at 4:13 PM Thomas Monjalon <thomas@monjalon.net> wrote:
> > > > 07/06/2021 09:20, Wang, Haiyue:
> > > > > From: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>
> > > > > > If we keep CXL in mind, I would imagine that in the future the devices on PCIe could have their own
> > > > > > local memory. May be some of the APIs could use generic names. For ex: instead of calling it as
> > > > > > "rte_gpu_malloc" may be we could call it as "rte_dev_malloc". This way any future device which hosts
> > > > > > its own memory that need to be managed by the application, can use these APIs.
> > > > > >
> > > > >
> > > > > "rte_dev_malloc" sounds a good name,
> > > >
> > > > Yes I like the idea.
> > > > 2 concerns:
> > > >
> > > > 1/ Device memory allocation requires a device handle.
> > > > So far we avoided exposing rte_device to the application.
> > > > How should we get a device handle from a DPDK application?
> > >
> > > Each device behaves differently at this level. In the view of the
> > > generic application, the architecture should like
> > >
> > > < Use DPDK subsystem as rte_ethdev, rte_bbdev etc for SPECIFIC function >
> > > ^
> > > |
> > > < DPDK driver>
> > > ^
> > > |
> > > <rte_device with this new callbacks >
> >
> > I think the formatting went wrong above.
> >
> > I would add more to the block diagram:
> >
> > class device API      - computing device API
> >         |            |              |
> > class device driver -   computing device driver
> >         |                           |
> >        EAL device with memory callback
> >
> > The idea above is that the class device driver can use services
> > of the new computing device library.
> 
> Yes. The question is, do we need any public DPDK _application_ APIs for that?

To have something generic!

> If it is public API then the scope is much bigger than that as the application
> can use it directly and it makes it non portable.

It is a non-sense. If we make an API, it will be better portable.
The only part which is non-portable is the program on the device
which may be different per computing device.
The synchronization with the DPDK application should be portable
if we define some good API.

> if the scope is only, the class driver consumption then the existing
> "bus"  _kind of_
> abstraction/API makes sense to me.
> 
> Where it abstracts,
> -FW download of device
> -Memory management of device
> -Opaque way to enq/deque jobs to the device.
> 
> And above should be consumed by "class driver" not "application".
> 
> If the application doing do that, we are in rte_raw device territory.

I'm sorry I don't understand what you make such assertion.
It seems you don't want generic API (which is the purpose of DPDK).