[patch 39/43] drm/i915: dont enable vblanks on disabled pipes

[Greg KH]

2.6.28-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Jesse Barnes <jbarnes@xxxxxxxxxxxxxxxx>

commit 71e0ffa599f54058d9b8724b4b14d0486751681d upstream.

In some cases userland may be confused and try to wait on vblank events from
pipes that aren't actually enabled.  We shouldn't allow this, so return
-EINVAL if the pipe isn't on.

Signed-off-by: Jesse Barnes <jbarnes@xxxxxxxxxxxxxxxx>
Signed-off-by: Eric Anholt <eric@xxxxxxxxxx>
Signed-off-by: Dave Airlie <airlied@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 drivers/gpu/drm/i915/i915_irq.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -400,6 +400,12 @@ int i915_enable_vblank(struct drm_device
 {
 	drm_i915_private_t *dev_priv = (drm_i915_private_t *) dev->dev_private;
 	unsigned long irqflags;
+	int pipeconf_reg = (pipe == 0) ? PIPEACONF : PIPEBCONF;
+	u32 pipeconf;
+
+	pipeconf = I915_READ(pipeconf_reg);
+	if (!(pipeconf & PIPEACONF_ENABLE))
+		return -EINVAL;
 
 	spin_lock_irqsave(&dev_priv->user_irq_lock, irqflags);
 	if (IS_I965G(dev))


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