drm/i915/crc: implement get_crc_sources callback

This patch implements get_crc_sources callback, which returns list of
all the valid crc sources supported by driver in current platform.

Changes since V1:
 - Return array of crc sources
Signed-off-by: Mahesh Kumar <mahesh1.kumar@intel.com>
Cc: dri-devel@lists.freedesktop.org
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180713135942.25061-8-mahesh1.kumar@intel.com

drivers/gpu/drm/i915/intel_display.c

@@ -12866,6 +12866,7 @@ static const struct drm_crtc_funcs intel_crtc_funcs = {
 	.atomic_destroy_state = intel_crtc_destroy_state,
 	.set_crc_source = intel_crtc_set_crc_source,
 	.verify_crc_source = intel_crtc_verify_crc_source,
+	.get_crc_sources = intel_crtc_get_crc_sources,
 };
 
 struct wait_rps_boost {

drivers/gpu/drm/i915/intel_drv.h

@@ -2155,11 +2155,14 @@ int intel_crtc_set_crc_source(struct drm_crtc *crtc, const char *source_name,
 			      size_t *values_cnt);
 int intel_crtc_verify_crc_source(struct drm_crtc *crtc,
 				 const char *source_name, size_t *values_cnt);
+const char *const *intel_crtc_get_crc_sources(struct drm_crtc *crtc,
+					      size_t *count);
 void intel_crtc_disable_pipe_crc(struct intel_crtc *crtc);
 void intel_crtc_enable_pipe_crc(struct intel_crtc *crtc);
 #else
 #define intel_crtc_set_crc_source NULL
 #define intel_crtc_verify_crc_source NULL
+#define intel_crtc_get_crc_sources NULL
 static inline void intel_crtc_disable_pipe_crc(struct intel_crtc *crtc)
 {
 }

drivers/gpu/drm/i915/intel_pipe_crc.c

@@ -1001,6 +1001,13 @@ intel_is_valid_crc_source(struct drm_i915_private *dev_priv,
 		return ivb_crc_source_valid(dev_priv, source);
 }
 
+const char *const *intel_crtc_get_crc_sources(struct drm_crtc *crtc,
+					      size_t *count)
+{
+	*count = ARRAY_SIZE(pipe_crc_sources);
+	return pipe_crc_sources;
+}
+
 int intel_crtc_verify_crc_source(struct drm_crtc *crtc, const char *source_name,
 				 size_t *values_cnt)
 {