[Intel-gfx] [PATCH 10/12] drm: Don't allow multiple buffers fb with stereo modes

[Damien Lespiau]

There are a few things to be flushed out if we want to allow multiple
buffers stereo framebuffers:
  - What with drm_planes? what semantics do they follow, what is the
    hardware able to do with them?
  - How do we define which buffer if the right/left one
  - Do we allow flips between 1 buffer fbs and 2 buffers fbs (No.)

So for now, and until I get access to hardware that can do that, let's
just disallow 2 buffers stereo framebuffers to not introduce ABI we
wouldn't be able to change afterwards.

Signed-off-by: Damien Lespiau <damien.lespiau at intel.com>
---
 drivers/gpu/drm/drm_crtc.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index 39f60ec..91d1c4b 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -2131,6 +2131,17 @@ int drm_mode_setcrtc(struct drm_device *dev, void *data,
 			goto out;
 		}
 
+		/*
+		 * Do not allow the use of framebuffers consisting of multiple
+		 * buffers with stereo modes until all the details API details
+		 * are fleshed out (eg. interaction with drm_planes, switch
+		 * between a 1 buffers and a 2 buffers fb, ...)
+		 */
+		if (fb->num_buffers > 1 && drm_mode_is_stereo(mode)) {
+			ret = -EINVAL;
+			goto out;
+		}
+
 		drm_mode_set_crtcinfo(mode, CRTC_INTERLACE_HALVE_V);
 
 		hdisplay = mode->hdisplay;
-- 
1.8.3.1