[Intel-gfx] [PATCH] drm/i915: Check mask/bit helper functions

[Daniel Vetter]

After a bit of irc discussion we've concluded that it would be prudent
to check that callers use the mask/enable paramters correctly. So add
a WARN_ON.

Now most callers have static parameters, so even better would be if we
could bug at compile-time. Hence improve the i915 WARN_ON to
BUILD_BUG_ON if the condition can be statically determined. Thanks to
Chris for this suggestion.

All this spurred by Damien's bugfix which added _MASKED_FIELD.

Cc: Damien Lespiau <damien.lespiau at intel.com>
Cc: Chris Wilson <chris at chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h | 9 ++++++++-
 drivers/gpu/drm/i915/i915_irq.c | 6 ++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 95dfa2dd35b9..e5d9d6642b09 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -57,8 +57,15 @@
 #define DRIVER_DESC		"Intel Graphics"
 #define DRIVER_DATE		"20141205"
 
+static inline bool __i915_warn_on(bool cond, const char *str)
+{
+	if (__builtin_constant_p(cond))
+		BUILD_BUG_ON(cond);
+	return WARN(cond, str);
+}
+
 #undef WARN_ON
-#define WARN_ON(x)		WARN(x, "WARN_ON(" #x ")")
+#define WARN_ON(x) __i915_warn_on((x), "WARN_ON(" #x ")")
 
 enum pipe {
 	INVALID_PIPE = -1,
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 08a5a4ba52ac..e6a1db36928e 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -183,6 +183,8 @@ static void ilk_update_gt_irq(struct drm_i915_private *dev_priv,
 {
 	assert_spin_locked(&dev_priv->irq_lock);
 
+	WARN_ON(enabled_irq_mask & ~interrupt_mask);
+
 	if (WARN_ON(!intel_irqs_enabled(dev_priv)))
 		return;
 
@@ -229,6 +231,8 @@ static void snb_update_pm_irq(struct drm_i915_private *dev_priv,
 {
 	uint32_t new_val;
 
+	WARN_ON(enabled_irq_mask & ~interrupt_mask);
+
 	assert_spin_locked(&dev_priv->irq_lock);
 
 	new_val = dev_priv->pm_irq_mask;
@@ -328,6 +332,8 @@ void ibx_display_interrupt_update(struct drm_i915_private *dev_priv,
 	sdeimr &= ~interrupt_mask;
 	sdeimr |= (~enabled_irq_mask & interrupt_mask);
 
+	WARN_ON(enabled_irq_mask & ~interrupt_mask);
+
 	assert_spin_locked(&dev_priv->irq_lock);
 
 	if (WARN_ON(!intel_irqs_enabled(dev_priv)))
-- 
2.1.1