staging: bcm2835-camera: Convert client_context field to a 32 bit handle

The client_context field is passed around which is really just a pointer
to a msg_context.  A lookup table mechanism for msg_context was added
previously, so convert this field to a handle as well.

The firmware never interperates the client_context, just passed it back.
Signed-off-by: Michael Zoran <mzoran@crowfest.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/vc04_services/bcm2835-camera/mmal-msg.h

@@ -250,7 +250,7 @@ struct mmal_driver_buffer {
 	u32 magic;
 	u32 component_handle;
 	u32 port_handle;
-	void *client_context;
+	u32 client_context;
 };
 
 /* buffer header */

drivers/staging/vc04_services/bcm2835-camera/mmal-vchiq.c

@@ -532,7 +532,7 @@ buffer_from_host(struct vchiq_mmal_instance *instance,
 	m.u.buffer_from_host.drvbuf.magic = MMAL_MAGIC;
 	m.u.buffer_from_host.drvbuf.component_handle = port->component->handle;
 	m.u.buffer_from_host.drvbuf.port_handle = port->handle;
-	m.u.buffer_from_host.drvbuf.client_context = msg_context;
+	m.u.buffer_from_host.drvbuf.client_context = msg_context->handle;
 
 	/* buffer header */
 	m.u.buffer_from_host.buffer_header.cmd = 0;
@@ -614,12 +614,20 @@ static void buffer_to_host_cb(struct vchiq_mmal_instance *instance,
 			      struct mmal_msg *msg, u32 msg_len)
 {
 	struct mmal_msg_context *msg_context;
+	u32 handle;
 
 	pr_debug("buffer_to_host_cb: instance:%p msg:%p msg_len:%d\n",
 		 instance, msg, msg_len);
 
 	if (msg->u.buffer_from_host.drvbuf.magic == MMAL_MAGIC) {
-		msg_context = msg->u.buffer_from_host.drvbuf.client_context;
+		handle = msg->u.buffer_from_host.drvbuf.client_context;
+		msg_context = lookup_msg_context(instance, handle);
+
+		if (!msg_context) {
+			pr_err("drvbuf.client_context(%u) is invalid\n",
+			       handle);
+			return;
+		}
 	} else {
 		pr_err("MMAL_MSG_TYPE_BUFFER_TO_HOST with bad magic\n");
 		return;