[Intel-gfx] [PATCH v4 2/2] drm/i915: Create dumb buffer from LMEM

[Chris Wilson]

Quoting Ramalingam C (2019-12-05 13:02:40)
> On 2019-12-05 at 12:20:12 +0000, Chris Wilson wrote:
> > Quoting Matthew Auld (2019-12-05 12:12:19)
> > > We would still need to clear the object(maybe I915_BO_ALLOC_CLEARED?)
> > > in order to pass the IGTs. We also need to adjust dumb_buffer.c, since
> > > that uses get_avail_ram_mb() for always_clear, but maybe we need the
> > > query region uapi for that?
> > 
> > Hmm. Questions over the maximum size for dumb buffer, maximum number of
> > dumb buffers, etc, should be addressed to the dumb API. So some form of
> > drmGetCap() ?
> Chris, Is this suggestion to add this capability probing through a new IOCTL for
> dumb APIs? Please clarify.

I don't think we need a new ioctl, as drm_getcap already covers the dumb
buffer API. We just need to expose the limits of the dumb buffer API
through it.

The 2 that spring to mind are maximum size of individual buffer and
maximum size of total dumb buffers. (The latter may be infinite for
drivers that allow swapping of inactive buffers.) There was a request on
irc for something like this as well, but I'm not aware of the context.
-Chris