drm/i915: fix potential dangling else problems in for_each_ macros

We have serious dangling else bugs waiting to happen in our for_each_
style macros with ifs. Consider, for example,

 #define for_each_power_domain(domain, mask)                         \
         for ((domain) = 0; (domain) < POWER_DOMAIN_NUM; (domain)++) \
                 if ((1 << (domain)) & (mask))

If this is used in context:

	if (condition)
		for_each_power_domain(domain, mask);
	else
		foo();

foo() will be called for each domain *not* in mask, if condition holds,
and not at all if condition doesn't hold.

Fix this by reversing the conditions in the macros, and adding an else
branch for the "for each" block, so that other if/else blocks can't
interfere. Provide a "for_each_if" helper macro to make it easier to get
this right.

v2: move for_each_if to drmP.h in a separate patch.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1448392916-2281-2-git-send-email-jani.nikula@intel.com
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 6 insertions, 6 deletions

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 95bb27de774f..fd88060b2596 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -288,7 +288,7 @@ struct i915_hotplug {
 	list_for_each_entry(intel_plane,				\
 			    &(dev)->mode_config.plane_list,		\
 			    base.head)					\
-		if ((intel_plane)->pipe == (intel_crtc)->pipe)
+		for_each_if ((intel_plane)->pipe == (intel_crtc)->pipe)
 
 #define for_each_intel_crtc(dev, intel_crtc) \
 	list_for_each_entry(intel_crtc, &dev->mode_config.crtc_list, base.head)
@@ -305,15 +305,15 @@ struct i915_hotplug {
 
 #define for_each_encoder_on_crtc(dev, __crtc, intel_encoder) \
 	list_for_each_entry((intel_encoder), &(dev)->mode_config.encoder_list, base.head) \
-		if ((intel_encoder)->base.crtc == (__crtc))
+		for_each_if ((intel_encoder)->base.crtc == (__crtc))
 
 #define for_each_connector_on_encoder(dev, __encoder, intel_connector) \
 	list_for_each_entry((intel_connector), &(dev)->mode_config.connector_list, base.head) \
-		if ((intel_connector)->base.encoder == (__encoder))
+		for_each_if ((intel_connector)->base.encoder == (__encoder))
 
 #define for_each_power_domain(domain, mask)				\
 	for ((domain) = 0; (domain) < POWER_DOMAIN_NUM; (domain)++)	\
-		if ((1 << (domain)) & (mask))
+		for_each_if ((1 << (domain)) & (mask))
 
 struct drm_i915_private;
 struct i915_mm_struct;
@@ -734,7 +734,7 @@ struct intel_uncore {
 	for ((i__) = 0, (domain__) = &(dev_priv__)->uncore.fw_domain[0]; \
 	     (i__) < FW_DOMAIN_ID_COUNT; \
 	     (i__)++, (domain__) = &(dev_priv__)->uncore.fw_domain[i__]) \
-		if (((mask__) & (dev_priv__)->uncore.fw_domains) & (1 << (i__)))
+		for_each_if (((mask__) & (dev_priv__)->uncore.fw_domains) & (1 << (i__)))
 
 #define for_each_fw_domain(domain__, dev_priv__, i__) \
 	for_each_fw_domain_mask(domain__, FORCEWAKE_ALL, dev_priv__, i__)
@@ -1979,7 +1979,7 @@ static inline struct drm_i915_private *guc_to_i915(struct intel_guc *guc)
 /* Iterate over initialised rings */
 #define for_each_ring(ring__, dev_priv__, i__) \
 	for ((i__) = 0; (i__) < I915_NUM_RINGS; (i__)++) \
-		if (((ring__) = &(dev_priv__)->ring[(i__)]), intel_ring_initialized((ring__)))
+		for_each_if ((((ring__) = &(dev_priv__)->ring[(i__)]), intel_ring_initialized((ring__))))
 
 enum hdmi_force_audio {
 	HDMI_AUDIO_OFF_DVI = -2,	/* no aux data for HDMI-DVI converter */