drm/i915: Keep a list of all contexts

I have implemented this patch before without creating a separate list
(I'm having trouble finding the links, but the messages ids are:
<1364942743-6041-2-git-send-email-ben@bwidawsk.net>
<1365118914-15753-9-git-send-email-ben@bwidawsk.net>)

However, the code is much simpler to just use a list and it makes the
code from the next patch a lot more pretty.

As you'll see in the next patch, the reason for this is to be able to
specify when a context needs to get L3 remapping. More details there.

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 1d77624..ada0950 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -1442,6 +1442,7 @@
 	struct drm_device *dev = node->minor->dev;
 	drm_i915_private_t *dev_priv = dev->dev_private;
 	struct intel_ring_buffer *ring;
+	struct i915_hw_context *ctx;
 	int ret, i;
 
 	ret = mutex_lock_interruptible(&dev->mode_config.mutex);
@@ -1460,12 +1461,14 @@
 		seq_putc(m, '\n');
 	}
 
-	for_each_ring(ring, dev_priv, i) {
-		if (ring->default_context) {
-			seq_printf(m, "HW default context %s ", ring->name);
-			describe_obj(m, ring->default_context->obj);
-			seq_putc(m, '\n');
-		}
+	list_for_each_entry(ctx, &dev_priv->context_list, link) {
+		seq_puts(m, "HW context ");
+		for_each_ring(ring, dev_priv, i)
+			if (ring->default_context == ctx)
+				seq_printf(m, "(default context %s) ", ring->name);
+
+		describe_obj(m, ctx->obj);
+		seq_putc(m, '\n');
 	}
 
 	mutex_unlock(&dev->mode_config.mutex);