Embed a struct ttm_buffer_object into the i915 gem object, making sure we alias the gem object part. It's a bit unfortunate that the struct ttm_buffer_ojbect embeds a gem object since we otherwise could make the TTM part private to the TTM backend, and use the usual i915 gem object for the other backends. To make this a bit more storage efficient for the other backends, we'd have to use a pointer for the gem object which would require a lot of changes in the driver. We postpone that for later.
Signed-off-by: Thomas Hellström thomas.hellstrom@linux.intel.com --- drivers/gpu/drm/i915/gem/i915_gem_object.c | 7 +++++++ drivers/gpu/drm/i915/gem/i915_gem_object_types.h | 12 +++++++++++- 2 files changed, 18 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.c b/drivers/gpu/drm/i915/gem/i915_gem_object.c index abadf0994ad0..c8953e3f5c70 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_object.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_object.c @@ -62,6 +62,13 @@ void i915_gem_object_init(struct drm_i915_gem_object *obj, const struct drm_i915_gem_object_ops *ops, struct lock_class_key *key, unsigned flags) { + /* + * A gem object is embedded both in a struct ttm_buffer_object :/ and + * in a drm_i915_gem_object. Make sure they are aliased. + */ + BUILD_BUG_ON(offsetof(typeof(*obj), base) != + offsetof(typeof(*obj), __do_not_access.base)); + spin_lock_init(&obj->vma.lock); INIT_LIST_HEAD(&obj->vma.list);
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h index dbd7fffe956e..98f69d8fd37d 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h +++ b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h @@ -10,6 +10,7 @@ #include <linux/mmu_notifier.h>
#include <drm/drm_gem.h> +#include <drm/ttm/ttm_bo_api.h> #include <uapi/drm/i915_drm.h>
#include "i915_active.h" @@ -99,7 +100,16 @@ struct i915_gem_object_page_iter { };
struct drm_i915_gem_object { - struct drm_gem_object base; + /* + * We might have reason to revisit the below since it wastes + * a lot of space for non-ttm gem objects. + * In any case, always use the accessors for the ttm_buffer_object + * when accessing it. + */ + union { + struct drm_gem_object base; + struct ttm_buffer_object __do_not_access; + };
const struct drm_i915_gem_object_ops *ops;