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>

drivers/gpu/drm/i915/i915_dma.c

@@ -1358,6 +1358,7 @@ struct drm_ioctl_desc i915_ioctls[] = {
 	DRM_IOCTL_DEF(DRM_I915_GEM_SET_TILING, i915_gem_set_tiling, 0),
 	DRM_IOCTL_DEF(DRM_I915_GEM_GET_TILING, i915_gem_get_tiling, 0),
 	DRM_IOCTL_DEF(DRM_I915_GEM_GET_APERTURE, i915_gem_get_aperture_ioctl, 0),
+	DRM_IOCTL_DEF(DRM_I915_GET_PIPE_FROM_CRTC_ID, intel_get_pipe_from_crtc_id, 0),
 };
 
 int i915_max_ioctl = DRM_ARRAY_SIZE(i915_ioctls);

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;

drivers/gpu/drm/i915/intel_drv.h

@@ -125,6 +125,8 @@ extern struct drm_encoder *intel_best_encoder(struct drm_connector *connector);
 
 extern struct drm_display_mode *intel_crtc_mode_get(struct drm_device *dev,
 						    struct drm_crtc *crtc);
+int intel_get_pipe_from_crtc_id(struct drm_device *dev, void *data,
+				struct drm_file *file_priv);
 extern void intel_wait_for_vblank(struct drm_device *dev);
 extern struct drm_crtc *intel_get_crtc_from_pipe(struct drm_device *dev, int pipe);
 extern struct drm_crtc *intel_get_load_detect_pipe(struct intel_output *intel_output,

include/drm/i915_drm.h

@@ -184,6 +184,7 @@ typedef struct _drm_i915_sarea {
 #define DRM_I915_GEM_GET_TILING	0x22
 #define DRM_I915_GEM_GET_APERTURE 0x23
 #define DRM_I915_GEM_MMAP_GTT	0x24
+#define DRM_I915_GET_PIPE_FROM_CRTC_ID	0x25
 
 #define DRM_IOCTL_I915_INIT		DRM_IOW( DRM_COMMAND_BASE + DRM_I915_INIT, drm_i915_init_t)
 #define DRM_IOCTL_I915_FLUSH		DRM_IO ( DRM_COMMAND_BASE + DRM_I915_FLUSH)
@@ -219,6 +220,7 @@ typedef struct _drm_i915_sarea {
 #define DRM_IOCTL_I915_GEM_SET_TILING	DRM_IOWR (DRM_COMMAND_BASE + DRM_I915_GEM_SET_TILING, struct drm_i915_gem_set_tiling)
 #define DRM_IOCTL_I915_GEM_GET_TILING	DRM_IOWR (DRM_COMMAND_BASE + DRM_I915_GEM_GET_TILING, struct drm_i915_gem_get_tiling)
 #define DRM_IOCTL_I915_GEM_GET_APERTURE	DRM_IOR  (DRM_COMMAND_BASE + DRM_I915_GEM_GET_APERTURE, struct drm_i915_gem_get_aperture)
+#define DRM_IOCTL_I915_GET_PIPE_FROM_CRTC_ID DRM_IOWR(DRM_COMMAND_BASE + DRM_I915_GET_PIPE_FROM_CRTC_ID, struct drm_intel_get_pipe_from_crtc_id)
 
 /* Allow drivers to submit batchbuffers directly to hardware, relying
  * on the security mechanisms provided by hardware.
@@ -657,4 +659,12 @@ struct drm_i915_gem_get_aperture {
 	__u64 aper_available_size;
 };
 
+struct drm_i915_get_pipe_from_crtc_id {
+	/** ID of CRTC being requested **/
+	__u32 crtc_id;
+
+	/** pipe of requested CRTC **/
+	__u32 pipe;
+};
+
 #endif				/* _I915_DRM_H_ */