[Intel-gfx] [PATCH v3] drm: Warn if plane/crtc/encoder/connector index exceeds our 32bit bitmasks

[Ville Syrjala]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

We use 32bit bitmasks to track planes/crtcs/encoders/connectors.
Naturally we can only do that if the index of those objects stays
below 32. Issue a warning whenever we exceed that limit, hopefully
prompting someone to fix the problem.

For connectors the issue is a bit more complicated as they can
be created/destroyed at runtime due to MST. So the problem is no
longer a purely theoretical programmer error. As the connector
indexes are allocated via ida, we can simply limit the maximum
value the ida is allowed to hand out. The error handling is already
in place.

v2: Return an error to the caller (Harry)
v3: Print a debug message so that we know what happened (Maarten)

Cc: Harry Wentland <harry.wentland at amd.com>
Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/drm_connector.c | 9 +++++++--
 drivers/gpu/drm/drm_crtc.c      | 4 ++++
 drivers/gpu/drm/drm_encoder.c   | 4 ++++
 drivers/gpu/drm/drm_plane.c     | 4 ++++
 4 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
index b85a7749709d..16b9c3810af2 100644
--- a/drivers/gpu/drm/drm_connector.c
+++ b/drivers/gpu/drm/drm_connector.c
@@ -205,9 +205,14 @@ int drm_connector_init(struct drm_device *dev,
 	connector->dev = dev;
 	connector->funcs = funcs;
 
-	ret = ida_simple_get(&config->connector_ida, 0, 0, GFP_KERNEL);
-	if (ret < 0)
+	/* connector index is used with 32bit bitmasks */
+	ret = ida_simple_get(&config->connector_ida, 0, 32, GFP_KERNEL);
+	if (ret < 0) {
+		DRM_DEBUG_KMS("Failed to allocate %s connector index: %d\n",
+			      drm_connector_enum_list[connector_type].name,
+			      ret);
 		goto out_put;
+	}
 	connector->index = ret;
 	ret = 0;
 
diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index f0556e654116..5b4be382a1d7 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -282,6 +282,10 @@ int drm_crtc_init_with_planes(struct drm_device *dev, struct drm_crtc *crtc,
 	WARN_ON(primary && primary->type != DRM_PLANE_TYPE_PRIMARY);
 	WARN_ON(cursor && cursor->type != DRM_PLANE_TYPE_CURSOR);
 
+	/* crtc index is used with 32bit bitmasks */
+	if (WARN_ON(config->num_crtc >= 32))
+		return -EINVAL;
+
 	crtc->dev = dev;
 	crtc->funcs = funcs;
 
diff --git a/drivers/gpu/drm/drm_encoder.c b/drivers/gpu/drm/drm_encoder.c
index 59e0ebe733f8..273e1c59c54a 100644
--- a/drivers/gpu/drm/drm_encoder.c
+++ b/drivers/gpu/drm/drm_encoder.c
@@ -110,6 +110,10 @@ int drm_encoder_init(struct drm_device *dev,
 {
 	int ret;
 
+	/* encoder index is used with 32bit bitmasks */
+	if (WARN_ON(dev->mode_config.num_encoder >= 32))
+		return -EINVAL;
+
 	ret = drm_mode_object_add(dev, &encoder->base, DRM_MODE_OBJECT_ENCODER);
 	if (ret)
 		return ret;
diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c
index 2c90519576a3..22b54663b6e7 100644
--- a/drivers/gpu/drm/drm_plane.c
+++ b/drivers/gpu/drm/drm_plane.c
@@ -173,6 +173,10 @@ int drm_universal_plane_init(struct drm_device *dev, struct drm_plane *plane,
 	unsigned int format_modifier_count = 0;
 	int ret;
 
+	/* plane index is used with 32bit bitmasks */
+	if (WARN_ON(config->num_total_plane >= 32))
+		return -EINVAL;
+
 	ret = drm_mode_object_add(dev, &plane->base, DRM_MODE_OBJECT_PLANE);
 	if (ret)
 		return ret;
-- 
2.13.6