Re: [PATCH 3/3] drm/i915: Add soft-pinning API for execbuffer

From: Jesse Barnes <jbarnes@virtuousgeek.org>
To: "Kristian Høgsberg" <krh@bitplanet.net>,
	"Chris Wilson" <chris@chris-wilson.co.uk>
Cc: "intel-gfx@lists.freedesktop.org" <intel-gfx@lists.freedesktop.org>
Subject: Re: [PATCH 3/3] drm/i915: Add soft-pinning API for execbuffer
Date: Thu, 5 Nov 2015 10:17:56 -0800	[thread overview]
Message-ID: <563B9D54.1080401@virtuousgeek.org> (raw)
In-Reply-To: <CAOeoa-fhQJ-12dxaOxThP1GDorrq4dhq=mJ9+cwsv=sfP+QTMw@mail.gmail.com>

On 11/05/2015 09:51 AM, Kristian Høgsberg wrote:
> On Tue, Oct 6, 2015 at 3:53 AM, Chris Wilson <chris@chris-wilson.co.uk> wrote:
>> Userspace can pass in an offset that it presumes the object is located
>> at. The kernel will then do its utmost to fit the object into that
>> location. The assumption is that userspace is handling its own object
>> locations (for example along with full-ppgtt) and that the kernel will
>> rarely have to make space for the user's requests.
> 
> I know the commit message isn't documentation, but the phrase "do its
> utmost" makes me uncomfortable. I'd like to be explicit about what
> might make it fail (should only be pinned fbs in case of aliased ppgtt
> or userspace errors such as overlapping placements), or conversely,
> spell out when the flag can be expected to work (full ppgtt).

Ooh yeah that would be good to add to the execbuf man page with the
softpin additions.  Oh wait, we don't have a man page for execbuf?
Someone should write one!

Jesse

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