rpmsg: glink: Add support for rpmsg glink chrdev

RPMSG provides a char device interface to userspace. Probe the rpmsg
chrdev channel to enable the rpmsg_ctrl device creation on glink
transports.
Signed-off-by: Chris Lew <clew@codeaurora.org>
Signed-off-by: Arun Kumar Neelakantam <aneela@codeaurora.org>
Signed-off-by: Deepak Kumar Singh <deesin@codeaurora.org>
Link: https://lore.kernel.org/r/1593017121-7953-4-git-send-email-deesin@codeaurora.orgSigned-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/rpmsg/qcom_glink_native.c

@@ -1574,6 +1574,40 @@ static void qcom_glink_cancel_rx_work(struct qcom_glink *glink)
 		kfree(dcmd);
 }
 
+static void qcom_glink_device_release(struct device *dev)
+{
+	struct rpmsg_device *rpdev = to_rpmsg_device(dev);
+	struct glink_channel *channel = to_glink_channel(rpdev->ept);
+
+	/* Release qcom_glink_alloc_channel() reference */
+	kref_put(&channel->refcount, qcom_glink_channel_release);
+	kfree(rpdev);
+}
+
+static int qcom_glink_create_chrdev(struct qcom_glink *glink)
+{
+	struct rpmsg_device *rpdev;
+	struct glink_channel *channel;
+
+	rpdev = kzalloc(sizeof(*rpdev), GFP_KERNEL);
+	if (!rpdev)
+		return -ENOMEM;
+
+	channel = qcom_glink_alloc_channel(glink, "rpmsg_chrdev");
+	if (IS_ERR(channel)) {
+		kfree(rpdev);
+		return PTR_ERR(channel);
+	}
+	channel->rpdev = rpdev;
+
+	rpdev->ept = &channel->ept;
+	rpdev->ops = &glink_device_ops;
+	rpdev->dev.parent = glink->dev;
+	rpdev->dev.release = qcom_glink_device_release;
+
+	return rpmsg_chrdev_register_device(rpdev);
+}
+
 struct qcom_glink *qcom_glink_native_probe(struct device *dev,
 					   unsigned long features,
 					   struct qcom_glink_pipe *rx,
@@ -1633,6 +1667,10 @@ struct qcom_glink *qcom_glink_native_probe(struct device *dev,
 	if (ret)
 		return ERR_PTR(ret);
 
+	ret = qcom_glink_create_chrdev(glink);
+	if (ret)
+		dev_err(glink->dev, "failed to register chrdev\n");
+
 	return glink;
 }
 EXPORT_SYMBOL_GPL(qcom_glink_native_probe);