[PATCH v10 06/11] drm: Add DRM client cap for aspect-ratio

[Nautiyal, Ankit K]

From: Ankit Nautiyal <ankit.k.nautiyal at intel.com>

To enable aspect-ratio support in DRM, blindly exposing the aspect
ratio information along with mode, can break things in existing
user-spaces which have no intention or support to use this aspect
ratio information.

To avoid this, a new drm client cap is required to enable a
user-space to advertise if it supports modes with aspect-ratio. Based
on this cap value, the kernel will take a call on exposing the aspect
ratio info in modes or not.

This patch adds the client cap for aspect-ratio.

Cc: Ville Syrjala <ville.syrjala at linux.intel.com>
Cc: Shashank Sharma <shashank.sharma at intel.com>
Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal at intel.com>

V3: rebase
V4: As suggested by Marteen Lankhorst modified the commit message
    explaining the need to use the DRM cap for aspect-ratio. Also,
    tweaked the comment lines in the code for better understanding and
    clarity, as recommended by Shashank Sharma.
V5: rebase
V6: rebase
V7: rebase
V8: rebase
V9: rebase
V10: added comment explaining that no userspace breaks on aspect-ratio
     mode bits.

Reviewed-by: Shashank Sharma <shashank.sharma at intel.com>
---
 drivers/gpu/drm/drm_ioctl.c | 9 +++++++++
 include/drm/drm_file.h      | 8 ++++++++
 include/uapi/drm/drm.h      | 7 +++++++
 3 files changed, 24 insertions(+)

diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
index af78291..39c8eab 100644
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c
@@ -325,6 +325,15 @@ drm_setclientcap(struct drm_device *dev, void *data, struct drm_file *file_priv)
 		file_priv->atomic = req->value;
 		file_priv->universal_planes = req->value;
 		break;
+	case DRM_CLIENT_CAP_ASPECT_RATIO:
+		if (req->value > 1)
+			return -EINVAL;
+	/*
+	 * No Atomic userspace blows up on aspect ratio mode bits. Checked in
+	 * wayland/weston, xserver, and hardware-composer modeset paths.
+	 */
+		file_priv->aspect_ratio_allowed = req->value;
+		break;
 	default:
 		return -EINVAL;
 	}
diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h
index 5176c37..02b7dde 100644
--- a/include/drm/drm_file.h
+++ b/include/drm/drm_file.h
@@ -182,6 +182,14 @@ struct drm_file {
 	unsigned atomic:1;
 
 	/**
+	 * @aspect_ratio_allowed:
+	 *
+	 * True, if client can handle picture aspect ratios, and has requested
+	 * to pass this information along with the mode.
+	 */
+	unsigned aspect_ratio_allowed:1;
+
+	/**
 	 * @is_master:
 	 *
 	 * This client is the creator of @master. Protected by struct
diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
index 6fdff59..9c660e1 100644
--- a/include/uapi/drm/drm.h
+++ b/include/uapi/drm/drm.h
@@ -680,6 +680,13 @@ struct drm_get_cap {
  */
 #define DRM_CLIENT_CAP_ATOMIC	3
 
+/**
+ * DRM_CLIENT_CAP_ASPECT_RATIO
+ *
+ * If set to 1, the DRM core will provide aspect ratio information in modes.
+ */
+#define DRM_CLIENT_CAP_ASPECT_RATIO    4
+
 /** DRM_IOCTL_SET_CLIENT_CAP ioctl argument type */
 struct drm_set_client_cap {
 	__u64 capability;
-- 
2.7.4