[Intel-gfx] [RFC 20/21] drm/i915: Convert 'ring_idle()' to use requests not seqnos

[Daniel Vetter]

On Tue, Oct 28, 2014 at 02:03:14PM +0000, John Harrison wrote:
> On 19/10/2014 15:09, Daniel Vetter wrote:
> >We have places that shovel stuff onto the ring without an explicit
> >add_request. Or at least we've had, so this needs a full audit, and that
> >audit needs to be in the commit message.
> Not sure what you mean. There is no functional change here. The old version
> pulled the seqno out of the last request entry in the list and compared that
> to the hardware seqno value to check for completion. The new version gets
> the same request entry and does the same completion test, just in request
> parlance. If commands are being dumped on the ring without an request being
> added to the request list then the old version would still not have been
> checking for them. It would still only look at the last piece of work that
> actually did call add_request and see if that has completed or not.

Oh, I've pretty badly mixed stuff up ;-)

The issue I'm seeing here though is acessing the request list, from irq
context, without any locks. Pre-existing, but still deserves a FIXME
comment.

Wrt the change itself I'm not sure it's that useful, this is fairly
low-level code.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch