It may not be obvious, but the current execbuffer2 ioctl interface
requires that the buffer object containing the batch-to-be-executed
be the LAST entry in the exec2_list[] array (I expected it to be
the first!).
To clarify this, we can replace the rather obscure construct
"list_entry(eb->vmas.prev, ...)"
in eb_get_batch() with the equivalent but more explicit
"list_last_entry(&eb->vmas,...)"
and of course add an explanatory comment.
Signed-off-by: Dave Gordon <david.s.gordon@xxxxxxxxx>
---
drivers/gpu/drm/i915/i915_gem_execbuffer.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 08bc37c..bc97670 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -1354,7 +1354,8 @@ static bool only_mappable_for_reloc(unsigned int flags)
static struct drm_i915_gem_object *
eb_get_batch(struct eb_vmas *eb)
{
- struct i915_vma *vma = list_entry(eb->vmas.prev, typeof(*vma), exec_list);
+ /* The batch is always the LAST item in the VMA list */
+ struct i915_vma *vma = list_last_entry(&eb->vmas, typeof(*vma), exec_list);
/*
* SNA is doing fancy tricks with compressing batch buffers, which leads
--
1.9.1
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