[PATCH 6/9] drm: Add a DRM_CAP_STEREO_3D capability for SET_CAP ioctl

[Damien Lespiau]

This capability allows user space to control the delivery of modes with
the 3D flags set. This is to not play games with current user space
users not knowing anything about stereo 3D flags and that could try
to set a mode with one or several of those bits set.

So, the plan is to remove the stereo 3D flags from the user mode
modeinfo structure by default, and let them through if we are being told
otherwise.

stereo_allowed is bound to the drm_file structure to make it a
per-client setting, not a global one.

Signed-off-by: Damien Lespiau <damien.lespiau at intel.com>
---
 drivers/gpu/drm/drm_crtc.c  | 16 +++++++++++++---
 drivers/gpu/drm/drm_ioctl.c | 14 +++++++++++++-
 include/drm/drmP.h          |  3 +++
 include/uapi/drm/drm.h      |  9 +++++++++
 4 files changed, 38 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index a691764..ff9646f 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -1257,12 +1257,14 @@ EXPORT_SYMBOL(drm_mode_group_init_legacy_group);
  * drm_crtc_convert_to_umode - convert a drm_display_mode into a modeinfo
  * @out: drm_mode_modeinfo struct to return to the user
  * @in: drm_display_mode to use
+ * @file_priv: drm file from the ioctl call
  *
  * Convert a drm_display_mode into a drm_mode_modeinfo structure to return to
  * the user.
  */
 static void drm_crtc_convert_to_umode(struct drm_mode_modeinfo *out,
-				      const struct drm_display_mode *in)
+				      const struct drm_display_mode *in,
+				      const struct drm_file *file_priv)
 {
 	WARN(in->hdisplay > USHRT_MAX || in->hsync_start > USHRT_MAX ||
 	     in->hsync_end > USHRT_MAX || in->htotal > USHRT_MAX ||
@@ -1287,6 +1289,13 @@ static void drm_crtc_convert_to_umode(struct drm_mode_modeinfo *out,
 	out->type = in->type;
 	strncpy(out->name, in->name, DRM_DISPLAY_MODE_LEN);
 	out->name[DRM_DISPLAY_MODE_LEN-1] = 0;
+
+	/*
+	 * If user-space hasn't configured the driver to expose the stereo 3D
+	 * flags, clear them.
+	 */
+	if (!file_priv->stereo_allowed)
+		out->flags &= ~DRM_MODE_FLAG_3D_MASK;
 }
 
 /**
@@ -1556,7 +1565,8 @@ int drm_mode_getcrtc(struct drm_device *dev,
 
 	if (crtc->enabled) {
 
-		drm_crtc_convert_to_umode(&crtc_resp->mode, &crtc->mode);
+		drm_crtc_convert_to_umode(&crtc_resp->mode, &crtc->mode,
+					  file_priv);
 		crtc_resp->mode_valid = 1;
 
 	} else {
@@ -1655,7 +1665,7 @@ int drm_mode_getconnector(struct drm_device *dev, void *data,
 		copied = 0;
 		mode_ptr = (struct drm_mode_modeinfo __user *)(unsigned long)out_resp->modes_ptr;
 		list_for_each_entry(mode, &connector->modes, head) {
-			drm_crtc_convert_to_umode(&u_mode, mode);
+			drm_crtc_convert_to_umode(&u_mode, mode, file_priv);
 			if (copy_to_user(mode_ptr + copied,
 					 &u_mode, sizeof(u_mode))) {
 				ret = -EFAULT;
diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
index e471cd9..a716641 100644
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c
@@ -304,7 +304,19 @@ int drm_getcap(struct drm_device *dev, void *data, struct drm_file *file_priv)
  */
 int drm_setcap(struct drm_device *dev, void *data, struct drm_file *file_priv)
 {
-	return -EINVAL;
+	struct drm_set_cap *req = data;
+
+	switch (req->capability) {
+	case DRM_CAP_STEREO_3D:
+		if (req->value > 1)
+			return -EINVAL;
+		file_priv->stereo_allowed = req->value;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
 }
 
 /**
diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index b9c321b..0df654c 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -431,6 +431,9 @@ struct drm_file {
 	struct drm_master *master; /* master this node is currently associated with
 				      N.B. not always minor->master */
 
+	/* true when the client has asked us to expose stereo 3D mode flags */
+	bool stereo_allowed;
+
 	/**
 	 * fbs - List of framebuffers associated with this file.
 	 *
diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
index d400e6f..23922b4 100644
--- a/include/uapi/drm/drm.h
+++ b/include/uapi/drm/drm.h
@@ -627,6 +627,15 @@ struct drm_get_cap {
 	__u64 value;
 };
 
+/**
+ * DRM_CAP_STEREO_3D
+ *
+ * if set to 1, the DRM core will expose the stereo 3D capabilities of the
+ * monitor by advertising the supported 3D layouts in the flags of struct
+ * drm_mode_modeinfo.
+ */
+#define DRM_CAP_STEREO_3D	1
+
 /** DRM_IOCTL_SET_CAP ioctl argument type */
 struct drm_set_cap {
 	__u64 capability;
-- 
1.8.3.1