drm/i915: Encapsulate kconfig constant values inside boolean predicates

Avoid angering clang and smatch by using a constant value in a '&&' test,
by forcing that constant value into a boolean.

E.g.,
drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c:159:13: warning: use of logical '&&' with constant operand [-Wconstant-logical-operand]
	if (!delay && CONFIG_DRM_I915_PREEMPT_TIMEOUT) {
                      ^  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Nathan Chancellor <natechancellor@gmail.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191025135943.12524-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/gem/i915_gem_context.c

@@ -325,7 +325,8 @@ static bool __cancel_engine(struct intel_engine_cs *engine)
 	 * kill the banned context, we fallback to doing a local reset
 	 * instead.
 	 */
-	if (CONFIG_DRM_I915_PREEMPT_TIMEOUT && !intel_engine_pulse(engine))
+	if (IS_ACTIVE(CONFIG_DRM_I915_PREEMPT_TIMEOUT) &&
+	    !intel_engine_pulse(engine))
 		return true;
 
 	/* If we are unable to send a pulse, try resetting this engine. */

drivers/gpu/drm/i915/gem/i915_gem_mman.c

@@ -312,7 +312,7 @@ vm_fault_t i915_gem_fault(struct vm_fault *vmf)
 		list_add(&obj->userfault_link, &i915->ggtt.userfault_list);
 	mutex_unlock(&i915->ggtt.vm.mutex);
 
-	if (CONFIG_DRM_I915_USERFAULT_AUTOSUSPEND)
+	if (IS_ACTIVE(CONFIG_DRM_I915_USERFAULT_AUTOSUSPEND))
 		intel_wakeref_auto(&i915->ggtt.userfault_wakeref,
 				   msecs_to_jiffies_timeout(CONFIG_DRM_I915_USERFAULT_AUTOSUSPEND));
 

drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c

@@ -133,7 +133,7 @@ static void heartbeat(struct work_struct *wrk)
 
 void intel_engine_unpark_heartbeat(struct intel_engine_cs *engine)
 {
-	if (!CONFIG_DRM_I915_HEARTBEAT_INTERVAL)
+	if (!IS_ACTIVE(CONFIG_DRM_I915_HEARTBEAT_INTERVAL))
 		return;
 
 	next_heartbeat(engine);
@@ -156,7 +156,7 @@ int intel_engine_set_heartbeat(struct intel_engine_cs *engine,
 	int err;
 
 	/* Send one last pulse before to cleanup persistent hogs */
-	if (!delay && CONFIG_DRM_I915_PREEMPT_TIMEOUT) {
+	if (!delay && IS_ACTIVE(CONFIG_DRM_I915_PREEMPT_TIMEOUT)) {
 		err = intel_engine_pulse(engine);
 		if (err)
 			return err;

drivers/gpu/drm/i915/i915_request.c

@@ -1447,7 +1447,7 @@ long i915_request_wait(struct i915_request *rq,
 	 * completion. That requires having a good predictor for the request
 	 * duration, which we currently lack.
 	 */
-	if (CONFIG_DRM_I915_SPIN_REQUEST &&
+	if (IS_ACTIVE(CONFIG_DRM_I915_SPIN_REQUEST) &&
 	    __i915_spin_request(rq, state, CONFIG_DRM_I915_SPIN_REQUEST)) {
 		dma_fence_signal(&rq->fence);
 		goto out;

drivers/gpu/drm/i915/i915_utils.h

@@ -430,4 +430,17 @@ static inline bool timer_expired(const struct timer_list *t)
 	return READ_ONCE(t->expires) && !timer_pending(t);
 }
 
+/*
+ * This is a lookalike for IS_ENABLED() that takes a kconfig value,
+ * e.g. CONFIG_DRM_I915_SPIN_REQUEST, and evaluates whether it is non-zero
+ * i.e. whether the configuration is active. Wrapping up the config inside
+ * a boolean context prevents clang and smatch from complaining about potential
+ * issues in confusing logical-&& with bitwise-& for constants.
+ *
+ * Sadly IS_ENABLED() itself does not work with kconfig values.
+ *
+ * Returns 0 if @config is 0, 1 if set to any value.
+ */
+#define IS_ACTIVE(config) ((config) != 0)
+
 #endif /* !__I915_UTILS_H */