drm/i915: simplify allocation of driver-internal requests

There are a number of places where the driver needs a request, but isn't
working on behalf of any specific user or in a specific context. At
present, we associate them with the per-engine default context. A future
patch will abolish those per-engine context pointers; but we can already
eliminate a lot of the references to them, just by making the allocator
allow NULL as a shorthand for "an appropriate context for this ring",
which will mean that the callers don't need to know anything about how
the "appropriate context" is found (e.g. per-ring vs per-device, etc).

So this patch renames the existing i915_gem_request_alloc(), and makes
it local (static inline), and replaces it with a wrapper that provides
a default if the context is NULL, and also has a nicer calling
convention (doesn't require a pointer to an output parameter). Then we
change all callers to use the new convention:
OLD:
	err = i915_gem_request_alloc(ring, user_ctx, &req);
	if (err) ...
NEW:
	req = i915_gem_request_alloc(ring, user_ctx);
	if (IS_ERR(req)) ...
OLD:
	err = i915_gem_request_alloc(ring, ring->default_context, &req);
	if (err) ...
NEW:
	req = i915_gem_request_alloc(ring, NULL);
	if (IS_ERR(req)) ...

v4:	Rebased

Signed-off-by: Dave Gordon <david.s.gordon@intel.com>
Reviewed-by: Nick Hoath <nicholas.hoath@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1453230175-19330-2-git-send-email-david.s.gordon@intel.com
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 4 insertions, 5 deletions

diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index faaf490..ec2482da 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -2520,11 +2520,10 @@ int intel_lr_context_deferred_alloc(struct intel_context *ctx,
 	if (ctx != ring->default_context && ring->init_context) {
 		struct drm_i915_gem_request *req;
 
-		ret = i915_gem_request_alloc(ring,
-			ctx, &req);
-		if (ret) {
-			DRM_ERROR("ring create req: %d\n",
-				ret);
+		req = i915_gem_request_alloc(ring, ctx);
+		if (IS_ERR(req)) {
+			ret = PTR_ERR(req);
+			DRM_ERROR("ring create req: %d\n", ret);
 			goto error_ringbuf;
 		}