drm/i915: rename & update eb_select_ring()

'ring' is an old deprecated term for a GPU engine, so we're trying to
phase out all such terminology. eb_select_ring() not only has 'ring'
(meaning engine) in its name, but it has an ugly calling convention
whereby it returns an errno and stores a pointer-to-engine indirectly
through an output parameter. As there is only one error it ever returns
(-EINVAL), we can make it return the pointer directly, and have the
caller pass back the error code -EINVAL if the pointer result is NULL.

Thus we can replace
-	ret = eb_select_ring(dev_priv, file, args, &engine);
-	if (ret)
-		return ret;
with
+	engine = eb_select_engine(dev_priv, file, args);
+	if (!engine)
+		return -EINVAL;
for increased clarity and maybe save a few cycles too.

Signed-off-by: Dave Gordon <david.s.gordon@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1469034967-15840-4-git-send-email-david.s.gordon@intel.com
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 6482ec2..f8d8ae3 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -1380,24 +1380,24 @@ static const enum intel_engine_id user_ring_map[I915_USER_RINGS + 1] = {
        [I915_EXEC_VEBOX]       = VECS
 };
 
-static int
-eb_select_ring(struct drm_i915_private *dev_priv,
-              struct drm_file *file,
-              struct drm_i915_gem_execbuffer2 *args,
-              struct intel_engine_cs **ring)
+static struct intel_engine_cs *
+eb_select_engine(struct drm_i915_private *dev_priv,
+                struct drm_file *file,
+                struct drm_i915_gem_execbuffer2 *args)
 {
        unsigned int user_ring_id = args->flags & I915_EXEC_RING_MASK;
+       struct intel_engine_cs *engine;
 
        if (user_ring_id > I915_USER_RINGS) {
                DRM_DEBUG("execbuf with unknown ring: %u\n", user_ring_id);
-               return -EINVAL;
+               return NULL;
        }
 
        if ((user_ring_id != I915_EXEC_BSD) &&
            ((args->flags & I915_EXEC_BSD_MASK) != 0)) {
                DRM_DEBUG("execbuf with non bsd ring but with invalid "
                          "bsd dispatch flags: %d\n", (int)(args->flags));
-               return -EINVAL;
+               return NULL;
        }
 
        if (user_ring_id == I915_EXEC_BSD && HAS_BSD2(dev_priv)) {
@@ -1412,20 +1412,20 @@ eb_select_ring(struct drm_i915_private *dev_priv,
                } else {
                        DRM_DEBUG("execbuf with unknown bsd ring: %u\n",
                                  bsd_idx);
-                       return -EINVAL;
+                       return NULL;
                }
 
-               *ring = &dev_priv->engine[_VCS(bsd_idx)];
+               engine = &dev_priv->engine[_VCS(bsd_idx)];
        } else {
-               *ring = &dev_priv->engine[user_ring_map[user_ring_id]];
+               engine = &dev_priv->engine[user_ring_map[user_ring_id]];
        }
 
-       if (!intel_engine_initialized(*ring)) {
+       if (!intel_engine_initialized(engine)) {
                DRM_DEBUG("execbuf with invalid ring: %u\n", user_ring_id);
-               return -EINVAL;
+               return NULL;
        }
 
-       return 0;
+       return engine;
 }
 
 static int
@@ -1467,9 +1467,9 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
        if (args->flags & I915_EXEC_IS_PINNED)
                dispatch_flags |= I915_DISPATCH_PINNED;
 
-       ret = eb_select_ring(dev_priv, file, args, &engine);
-       if (ret)
-               return ret;
+       engine = eb_select_engine(dev_priv, file, args);
+       if (!engine)
+               return -EINVAL;
 
        if (args->buffer_count < 1) {
                DRM_DEBUG("execbuf with %d buffers\n", args->buffer_count);