On 22/10/15 17:07, Chris Wilson wrote:
On Thu, Oct 22, 2015 at 03:15:55PM +0100, Tvrtko Ursulin wrote:
Hi,
On 21/10/15 16:24, Chris Wilson wrote:
Our GPUs impose certain requirements upon buffers that depend upon how
exactly they are used. Typically this is expressed as that they require
a larger surface than would be naively computed by pitch * height.
Normally such requirements are hidden away in the userspace driver, but
when we accept pointers from strangers and later impose extra conditions
on them, the original client allocator has no idea about the
monstrosities in the GPU and we require the userspace driver to inform
the kernel how many padding pages are required beyond the client
allocation.
v2: Long time, no see
[snip]
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index 08e047cba76a..678f7d5320ae 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -691,10 +691,11 @@ struct drm_i915_gem_exec_object2 {
#define EXEC_OBJECT_NEEDS_GTT (1<<1)
#define EXEC_OBJECT_WRITE (1<<2)
#define EXEC_OBJECT_SUPPORTS_48B_ADDRESS (1<<3)
-#define __EXEC_OBJECT_UNKNOWN_FLAGS -(EXEC_OBJECT_SUPPORTS_48B_ADDRESS<<1)
+#define EXEC_OBJECT_PAD_TO_SIZE (1<<4)
+#define __EXEC_OBJECT_UNKNOWN_FLAGS -(EXEC_OBJECT_PAD_TO_SIZE<<1)
__u64 flags;
- __u64 rsvd1;
+ __u64 rsvd1; /* pad_to_size */
__u64 rsvd2;
};
What do you think about:
union {
__u64 pad_to_size;
__u64 rsvd1;
} ?
Kind of like a migration path for userspace?
Hmm, I think that just might work. Clang? Does clang support anonymous
unions yet? Do we care if it doesn't?
I've found some existing examples in uapi headers so think we are covered.
Regards,
Tvrtko
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