[Mesa-dev] [PATCH 02/12] intel: Create intel_miptree_get_region() to prepare for fast color clear.

[Eric Anholt]

Paul Berry <stereotype441 at gmail.com> writes:

> With the advent of fast color clears, it will no longer be safe for
> the driver to access the data stored in a miptree with impunity.  For
> example, sometimes a resolve will need to be performed first (to
> ensure that deferred writes due to a fast clear are performed before
> the buffer is accessed).  Other times, fast clear will need to be
> disabled for the miptree, so that its contents can be safely shared
> with an entity that Mesa can't synchronize with easily.
>
> To prepare for that, this patch renames intel_mipmap_tree::region to
> intel_mipmap_tree::region_private and creates an accessor function,
> intel_miptree_get_region().  At the moment, the accessor function
> simply returns region_private.  Later in the patch series, this
> function will be expanded to take appropriate actions to maintain the
> proper fast color clear state.
>
> As much as possible, I've tried to restrict the functions which
> directly access region_private to low-level miptree functions
> (e.g. miptree initialization functions), so that it will be easy to
> verify that those functions access the miptree contents safely.

I don't like this change. I think we should be explicitly resolving at
the right points, like in patch 10.  In this patch, the places I see
that look like they could trigger a resolve from ACCESS_RENDER would all
break the GPU state, so you have to have things resolved before.  This
means that these intel_miptree_get_region() functions just freak me out
when I see them in some code -- "oh crap, would we resolve here?  that
would be bad... oh, looks like we prevent that over in this codepath
over here."

Once the places that should absolutely never resolve get removed,
there's hardly anything left in this patch.  It also goes against the
work I've done to kill the region struct.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 197 bytes
Desc: not available
URL: <http://lists.freedesktop.org/archives/mesa-dev/attachments/20130523/88eccab8/attachment.pgp>