[PATCH 5/6] drm/dp_mst: Hide drm_dp_mst_port contents from drivers

[Lyude Paul]

It hasn't been OK to access any of the contents of struct
drm_dp_mst_port without validating the port first for quite a long time
now, since a drm_dp_mst_port structure can be freed at any given moment
in time outside of the driver's contorl. Any kind of information a
driver needs from drm_dp_mst_port should be exposed through a helper
function instead that handles validating the port pointer, along with
anything else that's needed.

Since we've removed the last dangerous remanents of ->port accesses in
the DRM tree, let's finish this off and move the struct drm_dp_mst_port
definition out of drm_dp_mst_helper.h, into drm_dp_mst_topology.c, and
then replace it's header definition with an incomplete struct type. This
way drivers can still use the struct type, and no one else will make the
mistake of trying to access the contents of port.

Signed-off-by: Lyude Paul <lyude at redhat.com>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 59 ++++++++++++++++++++++++++
 include/drm/drm_dp_mst_helper.h       | 60 +--------------------------
 2 files changed, 60 insertions(+), 59 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 4336d17ce904..5fa898a8a64d 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -41,6 +41,65 @@
  * protocol. The helpers contain a topology manager and bandwidth manager.
  * The helpers encapsulate the sending and received of sideband msgs.
  */
+
+/**
+ * struct drm_dp_mst_port - MST port
+ * @kref: reference count for this port.
+ * @port_num: port number
+ * @input: if this port is an input port.
+ * @mcs: message capability status - DP 1.2 spec.
+ * @ddps: DisplayPort Device Plug Status - DP 1.2
+ * @pdt: Peer Device Type
+ * @ldps: Legacy Device Plug Status
+ * @dpcd_rev: DPCD revision of device on this port
+ * @num_sdp_streams: Number of simultaneous streams
+ * @num_sdp_stream_sinks: Number of stream sinks
+ * @available_pbn: Available bandwidth for this port.
+ * @next: link to next port on this branch device
+ * @mstb: branch device attach below this port
+ * @aux: i2c aux transport to talk to device connected to this port.
+ * @parent: branch device parent of this port
+ * @vcpi: Virtual Channel Payload info for this port.
+ * @connector: DRM connector this port is connected to.
+ * @mgr: topology manager this port lives under.
+ *
+ * This structure represents an MST port endpoint on a device somewhere
+ * in the MST topology.
+ */
+struct drm_dp_mst_port {
+	struct kref kref;
+
+	u8 port_num;
+	bool input;
+	bool mcs;
+	bool ddps;
+	u8 pdt;
+	bool ldps;
+	u8 dpcd_rev;
+	u8 num_sdp_streams;
+	u8 num_sdp_stream_sinks;
+	uint16_t available_pbn;
+	struct list_head next;
+	struct drm_dp_mst_branch *mstb; /* pointer to an mstb if this port has one */
+	struct drm_dp_aux aux; /* i2c bus for this port? */
+	struct drm_dp_mst_branch *parent;
+
+	struct drm_dp_vcpi vcpi;
+	struct drm_connector *connector;
+	struct drm_dp_mst_topology_mgr *mgr;
+
+	/**
+	 * @cached_edid: for DP logical ports - make tiling work by ensuring
+	 * that the EDID for all connectors is read immediately.
+	 */
+	struct edid *cached_edid;
+	/**
+	 * @has_audio: Tracks whether the sink connector to this port is
+	 * audio-capable.
+	 */
+	bool has_audio;
+};
+
 static bool dump_dp_payload_table(struct drm_dp_mst_topology_mgr *mgr,
 				  char *buf);
 static int test_calc_pbn_mode(void);
diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h
index 9cc93ea60e7e..3076a45aef4d 100644
--- a/include/drm/drm_dp_mst_helper.h
+++ b/include/drm/drm_dp_mst_helper.h
@@ -26,7 +26,7 @@
 #include <drm/drm_dp_helper.h>
 #include <drm/drm_atomic.h>
 
-struct drm_dp_mst_branch;
+struct drm_dp_mst_port;
 
 /**
  * struct drm_dp_vcpi - Virtual Channel Payload Identifier
@@ -42,64 +42,6 @@ struct drm_dp_vcpi {
 	int num_slots;
 };
 
-/**
- * struct drm_dp_mst_port - MST port
- * @kref: reference count for this port.
- * @port_num: port number
- * @input: if this port is an input port.
- * @mcs: message capability status - DP 1.2 spec.
- * @ddps: DisplayPort Device Plug Status - DP 1.2
- * @pdt: Peer Device Type
- * @ldps: Legacy Device Plug Status
- * @dpcd_rev: DPCD revision of device on this port
- * @num_sdp_streams: Number of simultaneous streams
- * @num_sdp_stream_sinks: Number of stream sinks
- * @available_pbn: Available bandwidth for this port.
- * @next: link to next port on this branch device
- * @mstb: branch device attach below this port
- * @aux: i2c aux transport to talk to device connected to this port.
- * @parent: branch device parent of this port
- * @vcpi: Virtual Channel Payload info for this port.
- * @connector: DRM connector this port is connected to.
- * @mgr: topology manager this port lives under.
- *
- * This structure represents an MST port endpoint on a device somewhere
- * in the MST topology.
- */
-struct drm_dp_mst_port {
-	struct kref kref;
-
-	u8 port_num;
-	bool input;
-	bool mcs;
-	bool ddps;
-	u8 pdt;
-	bool ldps;
-	u8 dpcd_rev;
-	u8 num_sdp_streams;
-	u8 num_sdp_stream_sinks;
-	uint16_t available_pbn;
-	struct list_head next;
-	struct drm_dp_mst_branch *mstb; /* pointer to an mstb if this port has one */
-	struct drm_dp_aux aux; /* i2c bus for this port? */
-	struct drm_dp_mst_branch *parent;
-
-	struct drm_dp_vcpi vcpi;
-	struct drm_connector *connector;
-	struct drm_dp_mst_topology_mgr *mgr;
-
-	/**
-	 * @cached_edid: for DP logical ports - make tiling work by ensuring
-	 * that the EDID for all connectors is read immediately.
-	 */
-	struct edid *cached_edid;
-	/**
-	 * @has_audio: Tracks whether the sink connector to this port is
-	 * audio-capable.
-	 */
-	bool has_audio;
-};
-
 /**
  * struct drm_dp_mst_branch - MST branch device.
  * @kref: reference count for this port.
-- 
2.19.1