linux-kernel - [PATCH] drm/i915: Mark wait_for_engine() as maybe

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Date:   Fri, 25 Aug 2017 10:09:45 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Daniel Vetter <daniel.vetter@...el.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        David Airlie <airlied@...ux.ie>
Cc:     intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org,
        Tvrtko Ursulin <tvrtko.ursulin@...el.com>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Nick Desaulniers <nick.desaulniers@...il.com>,
        Matthias Kaehlcke <mka@...omium.org>
Subject: [PATCH] drm/i915: Mark wait_for_engine() as maybe_unused

The only call of wait_for_engine() is wrapped in a GEM_WARN_ON macro,
which confusingly suppresses the call unless CONFIG_DRM_I915_DEBUG_GEM
is set.

According to http://www.spinics.net/lists/intel-gfx/msg128768.html the
current behavior is correct, even though it's not obvious. Different
solutions to improve GEM_WARN_ON were discussed, but no conclusion
was reached.

Mark wait_for_engine() as maybe_unused to avoid a compiler warning,
according to the above discussion this is still needed evein if
GEM_WARN_ON is eventually refactored.

Reported-by: Nick Desaulniers <nick.desaulniers@...il.com>
Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
---
 drivers/gpu/drm/i915/i915_gem.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 969bac8404f1..52d0b7d0082b 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3364,7 +3364,8 @@ static int wait_for_timeline(struct i915_gem_timeline *tl, unsigned int flags)
 	return 0;
 }
 
-static int wait_for_engine(struct intel_engine_cs *engine, int timeout_ms)
+static __maybe_unused int wait_for_engine(
+	struct intel_engine_cs *engine, int timeout_ms)
 {
 	return wait_for(intel_engine_is_idle(engine), timeout_ms);
 }
-- 
2.14.1.342.g6490525c54-goog