[PATCH v13 07/10] drm: Handle aspect ratio info in legacy modeset path

[Nautiyal, Ankit K]

From: Ankit Nautiyal <ankit.k.nautiyal at 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 at 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.
V13: Minor modifications as suggested by Ville.
---
 drivers/gpu/drm/drm_crtc.c          |  8 +++++++
 drivers/gpu/drm/drm_crtc_internal.h |  6 +++++
 drivers/gpu/drm/drm_modes.c         | 47 +++++++++++++++++++++++++++++++++++++
 3 files changed, 61 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_crtc_internal.h b/drivers/gpu/drm/drm_crtc_internal.h
index 5d307b2..31d6c77 100644
--- a/drivers/gpu/drm/drm_crtc_internal.h
+++ b/drivers/gpu/drm/drm_crtc_internal.h
@@ -222,3 +222,9 @@ int drm_mode_page_flip_ioctl(struct drm_device *dev,
 void drm_mode_fixup_1366x768(struct drm_display_mode *mode);
 void drm_reset_display_info(struct drm_connector *connector);
 u32 drm_add_display_info(struct drm_connector *connector, const struct edid *edid);
+
+/* drm_modes.c */
+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);
diff --git a/drivers/gpu/drm/drm_modes.c b/drivers/gpu/drm/drm_modes.c
index c395a24..2bf2f0b 100644
--- a/drivers/gpu/drm/drm_modes.c
+++ b/drivers/gpu/drm/drm_modes.c
@@ -1759,3 +1759,50 @@ 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)
+{
+	if (file_priv->aspect_ratio_allowed ||
+	    (umode->flags & DRM_MODE_FLAG_PIC_AR_MASK) == DRM_MODE_FLAG_PIC_AR_NONE)
+		return true;
+	return false;
+}
+
+/**
+ * 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;
+}
-- 
2.7.4