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

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Date:	Tue, 15 Jul 2014 10:29:33 -0400
From:	Jerome Glisse <j.glisse@...il.com>
To:	Dave Airlie <airlied@...il.com>
Cc:	Christian König <deathsimple@...afone.de>,
	"Bridgman, John" <John.Bridgman@....com>,
	"Lewycky, Andrew" <Andrew.Lewycky@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	"Deucher, Alexander" <Alexander.Deucher@....com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Subject: Re: [PATCH 00/83] AMD HSA kernel driver

On Tue, Jul 15, 2014 at 02:35:19PM +1000, Dave Airlie wrote:
> On 14 July 2014 18:37, Christian König <deathsimple@...afone.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


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