drm/i915: Add new GET_PIPE_FROM_CRTC_ID ioctl.

This allows userlevel code to discover the pipe number corresponding
to a given CRTC ID. This is necessary for doing pipe-specific
operations such as waiting for vblank on a given CRTC.  Failure to use
the right pipe mapping can result in GPU hangs, or at least failure
to actually sync to vblank.

Signed-off-by: Carl Worth <cworth@cworth.org>
[anholt: Style touchups from review]
Signed-off-by: Eric Anholt <eric@anholt.net>

1 files changed, 31 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index bdcda36953b0..3387cf32f385 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -1804,6 +1804,37 @@ static void intel_crtc_init(struct drm_device *dev, int pipe)
         }
 }
 
+int intel_get_pipe_from_crtc_id(struct drm_device *dev, void *data,
+                                struct drm_file *file_priv)
+{
+        drm_i915_private_t *dev_priv = dev->dev_private;
+        struct drm_i915_get_pipe_from_crtc_id *pipe_from_crtc_id = data;
+        struct drm_crtc *crtc = NULL;
+        int pipe = -1;
+
+        if (!dev_priv) {
+                DRM_ERROR("called with no initialization\n");
+                return -EINVAL;
+        }
+
+        list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
+                struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
+                if (crtc->base.id == pipe_from_crtc_id->crtc_id) {
+                        pipe = intel_crtc->pipe;
+                        break;
+                }
+        }
+
+        if (pipe == -1) {
+                DRM_ERROR("no such CRTC id\n");
+                return -EINVAL;
+        }
+
+        pipe_from_crtc_id->pipe = pipe;
+
+       return 0;
+}
+
 struct drm_crtc *intel_get_crtc_from_pipe(struct drm_device *dev, int pipe)
 {
         struct drm_crtc *crtc = NULL;