drm/bridge/sii8620: add continuations to messages

Due to asynchronous nature of MHL flow of execution is dispersed.
Logical continuation of some actions happens after response of peer,
i.e in interrupt handler. To simplify coding continuation mechanism
has been added - it is now possible to provide continuation callback,
which will be called after peer responds to given action.
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Archit Taneja <architt@codeaurora.org>
Link: http://patchwork.freedesktop.org/patch/msgid/1485935272-17337-5-git-send-email-a.hajda@samsung.com

drivers/gpu/drm/bridge/sil-sii8620.c

@@ -78,12 +78,15 @@ struct sii8620_mt_msg;
 typedef void (*sii8620_mt_msg_cb)(struct sii8620 *ctx,
 				  struct sii8620_mt_msg *msg);
 
+typedef void (*sii8620_cb)(struct sii8620 *ctx, int ret);
+
 struct sii8620_mt_msg {
 	struct list_head node;
 	u8 reg[4];
 	u8 ret;
 	sii8620_mt_msg_cb send;
 	sii8620_mt_msg_cb recv;
+	sii8620_cb continuation;
 };
 
 static const u8 sii8620_i2c_page[] = {
@@ -258,6 +261,8 @@ static void sii8620_mt_work(struct sii8620 *ctx)
 				       node);
 		if (msg->recv)
 			msg->recv(ctx, msg);
+		if (msg->continuation)
+			msg->continuation(ctx, msg->ret);
 		list_del(&msg->node);
 		kfree(msg);
 	}
@@ -310,6 +315,21 @@ static struct sii8620_mt_msg *sii8620_mt_msg_new(struct sii8620 *ctx)
 	return msg;
 }
 
+static void sii8620_mt_set_cont(struct sii8620 *ctx, sii8620_cb cont)
+{
+	struct sii8620_mt_msg *msg;
+
+	if (ctx->error)
+		return;
+
+	if (list_empty(&ctx->mt_queue)) {
+		ctx->error = -EINVAL;
+		return;
+	}
+	msg = list_last_entry(&ctx->mt_queue, struct sii8620_mt_msg, node);
+	msg->continuation = cont;
+}
+
 static void sii8620_mt_msc_cmd(struct sii8620 *ctx, u8 cmd, u8 arg1, u8 arg2)
 {
 	struct sii8620_mt_msg *msg = sii8620_mt_msg_new(ctx);