[PATCH v12 07/10] drm: Handle aspect ratio info in legacy modeset path

["Nautiyal, Ankit K" <ankit.k.nautiyal@intel.com>]

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

If the user-space does not support aspect-ratio, and requests for a
modeset with mode having aspect ratio bits set, then the given
user-mode must be rejected. Secondly, while preparing a user-mode from
kernel mode, the aspect-ratio info must not be given, if aspect-ratio
is not supported by the user.

This patch:
1. rejects the modes with aspect-ratio info, during modeset, if the
   user does not support aspect ratio.
2. does not load the aspect-ratio info in user-mode structure, if
   aspect ratio is not supported.
3. adds helper functions for determining if aspect-ratio is expected
   in user-mode and for allowing/disallowing the aspect-ratio, if its
   not expected.

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>

V3: Addressed review comments from Ville:
    Do not corrupt the current crtc state by updating aspect-ratio on
    the fly.
V4: rebase
V5: As suggested by Ville, rejected the modeset calls for modes with
    aspect ratio, if the user does not set aspect-ratio cap.
V6: Used the helper functions for determining if aspect-ratio is
    expected in the user-mode.
V7: rebase
V8: rebase
V9: rebase
v10: Modified the commit-message
v11: rebase
v12: Merged the patch for adding aspect-ratio helper functions
     with this patch.
---
 drivers/gpu/drm/drm_crtc.c  |  8 ++++++++
 drivers/gpu/drm/drm_modes.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
 include/drm/drm_modes.h     |  4 ++++
 3 files changed, 57 insertions(+)

diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index a231dd5..98323f4 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -449,6 +449,7 @@ int drm_mode_getcrtc(struct drm_device *dev,
 			crtc_resp->mode_valid = 0;
 		}
 	}
+	drm_mode_filter_aspect_ratio_flags(file_priv, &crtc_resp->mode);
 	drm_modeset_unlock(&crtc->mutex);
 
 	return 0;
@@ -628,6 +629,13 @@ int drm_mode_setcrtc(struct drm_device *dev, void *data,
 			ret = -ENOMEM;
 			goto out;
 		}
+		if (!drm_mode_aspect_ratio_allowed(file_priv,
+						   &crtc_req->mode)) {
+			DRM_DEBUG_KMS("Unexpected aspect-ratio flag bits\n");
+			ret = -EINVAL;
+			goto out;
+		}
+
 
 		ret = drm_mode_convert_umode(dev, mode, &crtc_req->mode);
 		if (ret) {
diff --git a/drivers/gpu/drm/drm_modes.c b/drivers/gpu/drm/drm_modes.c
index c395a24..d6f68c8 100644
--- a/drivers/gpu/drm/drm_modes.c
+++ b/drivers/gpu/drm/drm_modes.c
@@ -1759,3 +1759,48 @@ bool drm_mode_is_420(const struct drm_display_info *display,
 		drm_mode_is_420_also(display, mode);
 }
 EXPORT_SYMBOL(drm_mode_is_420);
+
+/**
+ * drm_mode_aspect_ratio_allowed - checks if the aspect-ratio information
+ * is expected from the user-mode.
+ *
+ * If the user has set aspect-ratio cap, then the flag of the user-mode is
+ * allowed to contain aspect-ratio value.
+ * If the user does not set aspect-ratio cap, then the only value allowed in the
+ * flags bits is aspect-ratio NONE.
+ *
+ * @file_priv: file private structure to get the user capabilities
+ * @umode: drm_mode_modeinfo struct, whose flag carry the aspect ratio
+ * information.
+ *
+ * Returns:
+ * true if the aspect-ratio info is allowed in the user-mode flags.
+ * false, otherwise.
+ */
+bool
+drm_mode_aspect_ratio_allowed(const struct drm_file *file_priv,
+			      struct drm_mode_modeinfo *umode)
+{
+	return file_priv->aspect_ratio_allowed || (umode->flags &
+		DRM_MODE_FLAG_PIC_AR_MASK) == DRM_MODE_FLAG_PIC_AR_NONE;
+}
+
+/**
+ * drm_mode_filter_aspect_ratio_flags - filters the aspect-ratio bits in the
+ * user-mode flags.
+ *
+ * Checks if the aspect-ratio information is allowed. Resets the aspect-ratio
+ * bits in the user-mode flags, if aspect-ratio info is not allowed.
+ *
+ * @file_priv: file private structure to get the user capabilities.
+ * @umode: drm_mode_modeinfo struct, whose flags' aspect-ratio bits needs to
+ * be filtered.
+ *
+ */
+void
+drm_mode_filter_aspect_ratio_flags(const struct drm_file *file_priv,
+				   struct drm_mode_modeinfo *umode)
+{
+	if (!drm_mode_aspect_ratio_allowed(file_priv, umode))
+		umode->flags &= ~DRM_MODE_FLAG_PIC_AR_MASK;
+}
diff --git a/include/drm/drm_modes.h b/include/drm/drm_modes.h
index 2f78b7e..e0b060d 100644
--- a/include/drm/drm_modes.h
+++ b/include/drm/drm_modes.h
@@ -461,6 +461,10 @@ bool drm_mode_is_420_also(const struct drm_display_info *display,
 			  const struct drm_display_mode *mode);
 bool drm_mode_is_420(const struct drm_display_info *display,
 		     const struct drm_display_mode *mode);
+bool drm_mode_aspect_ratio_allowed(const struct drm_file *file_priv,
+				   struct drm_mode_modeinfo *umode);
+void drm_mode_filter_aspect_ratio_flags(const struct drm_file *file_priv,
+					struct drm_mode_modeinfo *umode);
 
 struct drm_display_mode *drm_cvt_mode(struct drm_device *dev,
 				      int hdisplay, int vdisplay, int vrefresh,
-- 
2.7.4

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