maintainer-feedback requested: [Bug 244877] graphics/mesa-dri: Fixing vulkan by switching to unsynchronized userptr ioctls

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Bug 244877: graphics/mesa-dri: Fixing vulkan by switching to unsynchronized
userptr ioctls
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=244877



--- Description ---
This is the userspace portion of a change which fixes the Vulkan graphics API
on older Intel machines:

https://github.com/FreeBSDDesktop/kms-drm/pull/205

The above PR fixes the unsychronized DRM_IOCTL_I915_GEM_USERPTR which is used
by intel's vulkan code. For the fix to be used the ioctl needs to have the
I915_USERPTR_UNSYNCHRONIZED flag enabled:

    struct drm_i915_gem_userptr userptr = {
       .user_ptr = (__u64)((unsigned long) mem),
       .user_size = size,
-      .flags = 0,
+      .flags = I915_USERPTR_UNSYNCHRONIZED,
    };

    int ret = anv_ioctl(device->fd, DRM_IOCTL_I915_GEM_USERPTR, &userptr);

I've needed both the PR and this change for some daily vulkan development to
work.

It seems that maybe all the mesa stuff is going to be overhauled soon? So maybe
this isn't the ideal time to merge this. Please let me know if there is
anything I can help with!