ttm_fbdev_mmap() just doesn't work.  It appears to work fine, mmap()
returns success, but any attempt to actually access the mapping causes a
SIGBUS.

We can just use drm_gem_prime_mmap() instead.  Almost.  We have to copy
over the start offset from the ttm_buffer_object vm_node to the
drm_gem_object vm_node so the offset math in drm_gem_prime_mmap() works
correctly for us even though we use ttm to manage our objects.

Signed-off-by: Gerd Hoffmann <kra...@redhat.com>
---
 drivers/gpu/drm/bochs/bochs_mm.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/bochs/bochs_mm.c b/drivers/gpu/drm/bochs/bochs_mm.c
index 641a33f134..49463348a0 100644
--- a/drivers/gpu/drm/bochs/bochs_mm.c
+++ b/drivers/gpu/drm/bochs/bochs_mm.c
@@ -442,5 +442,6 @@ int bochs_gem_prime_mmap(struct drm_gem_object *obj,
 {
        struct bochs_bo *bo = gem_to_bochs_bo(obj);
 
-       return ttm_fbdev_mmap(vma, &bo->bo);
+       bo->gem.vma_node.vm_node.start = bo->bo.vma_node.vm_node.start;
+       return drm_gem_prime_mmap(obj, vma);
 }
-- 
2.9.3

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