Re: [PATCH 00/83] AMD HSA kernel driver

[Jerome Glisse <j.glisse@gmail.com>]

On Tue, Jul 15, 2014 at 02:35:19PM +1000, Dave Airlie wrote:
> On 14 July 2014 18:37, Christian König <deathsimple@vodafone.de> wrote:
> >> I vote for HSA module that expose ioctl and is an intermediary with the
> >> kernel driver that handle the hardware. This gives a single point for
> >> HSA hardware and yes this enforce things for any hardware manufacturer.
> >> I am more than happy to tell them that this is it and nothing else if
> >> they want to get upstream.
> >
> > I think we should still discuss this single point of entry a bit more.
> >
> > Just to make it clear the plan is to expose all physical HSA capable devices
> > through a single /dev/hsa device node to userspace.
> 
> This is why we don't design kernel interfaces in secret foundations,
> and expect anyone to like them.
> 

I think at this time this is unlikely to get into 3.17. But Christian had
point on having multiple device file. So something like /dev/hsa/*

> So before we go any further, how is this stuff planned to work for
> multiple GPUs/accelerators?

My understanding is that you create queue and each queue is associated
with a device. You can create several queue for same device and have
different priority btw queue.

Btw queue here means a ring buffer that understand a common set of pm4
packet.

> Do we have a userspace to exercise this interface so we can see how
> such a thing would look?

I think we need to wait a bit before freezing and accepting the kernel
api and see enough userspace bits to be confortable. Moreover if AMD
wants common API for HSA i also think that they at very least needs
there HSA partner to make public comment on the kernel API.

Cheers,
Jérôme