Re: [PATCH 10/12] drm/i915: Allow ggtt lookups to not WARN

[Daniel Vetter <daniel@ffwll.ch>]

On Mon, Nov 25, 2013 at 09:54:41AM -0800, Ben Widawsky wrote:
> To be able to effectively use the GGTT object lookup function, we don't
> want to warn when there is no GGTT mapping. Let the caller deal with it
> instead.
> 
> Originally, I had intended to have this behavior, and has not
> introduced the WARN. It was introduced during review with the addition
> of the follow commit
> 
> commit 5c2abbeab798154166d42fce4f71790caa6dd9bc
> Author: Ben Widawsky <benjamin.widawsky@intel.com>
> Date:   Tue Sep 24 09:57:57 2013 -0700
> 
>     drm/i915: Provide a cheap ggtt vma lookup
> 
> Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
> ---
>  drivers/gpu/drm/i915/i915_gem.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index bc5c865..6388706 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -5069,7 +5069,7 @@ struct i915_vma *i915_gem_obj_to_ggtt(struct drm_i915_gem_object *obj)
>  		return NULL;
>  
>  	vma = list_first_entry(&obj->vma_list, typeof(*vma), vma_link);
> -	if (WARN_ON(vma->vm != obj_to_ggtt(obj)))
> +	if (vma->vm != obj_to_ggtt(obj))

Makes sense, but then please add a must_check annotation to this function.
That will point you at the user in the context code which imo deserves a
BUG_ON or similar. I guess we should also convert over the little ggtt
helpers to use this function.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch