[PATCH v2 5/8] rpmsg: introduce reserved rpmsg driver for ns announcement

[Arnaud Pouliquen <arnaud.pouliquen@st.com>]

The name service announcement should not be linked to the RPMsg virtio bus
but to the RPMsg protocol itself.

This patch proposes to break the dependency with the RPmsg virtio bus by
the introduction of the reserved RPMsg name service driver which will be in
charge of managing the RPMsg name service announcement.

This first patch only implements the probe and the RPMsg endpoint to
manage create and release channels remote requests.

Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
---
 drivers/rpmsg/Kconfig          |   8 ++
 drivers/rpmsg/Makefile         |   1 +
 drivers/rpmsg/rpmsg_internal.h |  17 +++++
 drivers/rpmsg/rpmsg_ns.c       | 135 +++++++++++++++++++++++++++++++++
 4 files changed, 161 insertions(+)
 create mode 100644 drivers/rpmsg/rpmsg_ns.c

diff --git a/drivers/rpmsg/Kconfig b/drivers/rpmsg/Kconfig
index f96716893c2a..c3fc75e6514b 100644
--- a/drivers/rpmsg/Kconfig
+++ b/drivers/rpmsg/Kconfig
@@ -15,6 +15,14 @@ config RPMSG_CHAR
 	  in /dev. They make it possible for user-space programs to send and
 	  receive rpmsg packets.
 
+config RPMSG_NS
+	tristate "RPMSG name service announcement"
+	depends on RPMSG
+	help
+	  Say Y here to enable the support of the name service announcement
+	  channel that probes the associated RPMsg device on remote endpoint
+	  service announcement.
+
 config RPMSG_MTK_SCP
 	tristate "MediaTek SCP"
 	depends on MTK_SCP
diff --git a/drivers/rpmsg/Makefile b/drivers/rpmsg/Makefile
index ffe932ef6050..8d452656f0ee 100644
--- a/drivers/rpmsg/Makefile
+++ b/drivers/rpmsg/Makefile
@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 obj-$(CONFIG_RPMSG)		+= rpmsg_core.o
 obj-$(CONFIG_RPMSG_CHAR)	+= rpmsg_char.o
+obj-$(CONFIG_RPMSG_NS)		+= rpmsg_ns.o
 obj-$(CONFIG_RPMSG_MTK_SCP)	+= mtk_rpmsg.o
 qcom_glink-objs			:= qcom_glink_native.o qcom_glink_ssr.o
 obj-$(CONFIG_RPMSG_QCOM_GLINK) += qcom_glink.o
diff --git a/drivers/rpmsg/rpmsg_internal.h b/drivers/rpmsg/rpmsg_internal.h
index d5ab286d0e5e..641b48f6bf2a 100644
--- a/drivers/rpmsg/rpmsg_internal.h
+++ b/drivers/rpmsg/rpmsg_internal.h
@@ -102,4 +102,21 @@ static inline int rpmsg_chrdev_register_device(struct rpmsg_device *rpdev)
 	return rpmsg_register_device(rpdev);
 }
 
+/**
+ * rpmsg_ns_register_device() - register name service device based on rpdev
+ * @rpdev: prepared rpdev to be used for creating endpoints
+ *
+ * This function wraps rpmsg_register_device() preparing the rpdev for use as
+ * basis for the rpmsg name service device.
+ */
+static inline int rpmsg_ns_register_device(struct rpmsg_device *rpdev)
+{
+	strcpy(rpdev->id.name, "rpmsg_ns");
+	rpdev->driver_override = "rpmsg_ns";
+	rpdev->src = RPMSG_NS_ADDR;
+	rpdev->dst = RPMSG_NS_ADDR;
+
+	return rpmsg_register_device(rpdev);
+}
+
 #endif
diff --git a/drivers/rpmsg/rpmsg_ns.c b/drivers/rpmsg/rpmsg_ns.c
new file mode 100644
index 000000000000..3c929b6976a6
--- /dev/null
+++ b/drivers/rpmsg/rpmsg_ns.c
@@ -0,0 +1,135 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) STMicroelectronics 2020 - All Rights Reserved
+ */
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include "rpmsg_internal.h"
+
+/**
+ * enum rpmsg_ns_flags - dynamic name service announcement flags
+ *
+ * @RPMSG_NS_CREATE: a new remote service was just created
+ * @RPMSG_NS_DESTROY: a known remote service was just destroyed
+ */
+enum rpmsg_ns_flags {
+	RPMSG_NS_CREATE		= 0,
+	RPMSG_NS_DESTROY	= 1,
+};
+
+/**
+ * struct rpmsg_ns_msg - dynamic name service announcement message
+ * @name: name of remote service that is published
+ * @addr: address of remote service that is published
+ * @flags: indicates whether service is created or destroyed
+ *
+ * This message is sent across to publish a new service, or announce
+ * about its removal. When we receive these messages, an appropriate
+ * rpmsg channel (i.e device) is created/destroyed. In turn, the ->probe()
+ * or ->remove() handler of the appropriate rpmsg driver will be invoked
+ * (if/as-soon-as one is registered).
+ */
+struct rpmsg_ns_msg {
+	char name[RPMSG_NAME_SIZE];
+	__le32 addr;
+	__le32 flags;
+} __packed;
+
+/* Invoked when a name service announcement arrives */
+static int rpmsg_ns_cb(struct rpmsg_device *rpdev, void *data, int len,
+		       void *priv, u32 src)
+{
+	struct rpmsg_ns_msg *msg = data;
+	struct rpmsg_device *newch;
+	struct rpmsg_channel_info chinfo;
+	struct device *dev = &rpdev->dev;
+	unsigned int flags = le32_to_cpu(msg->flags);
+	int ret;
+
+#if defined(CONFIG_DYNAMIC_DEBUG)
+	dynamic_hex_dump("NS announcement: ", DUMP_PREFIX_NONE, 16, 1,
+			 data, len, true);
+#endif
+
+	if (len != sizeof(*msg)) {
+		dev_err(dev, "malformed ns msg (%d)\n", len);
+		return -EINVAL;
+	}
+
+	/* Don't trust the remote processor for null terminating the name */
+	msg->name[RPMSG_NAME_SIZE - 1] = '\0';
+
+	strncpy(chinfo.name, msg->name, sizeof(chinfo.name));
+	chinfo.src = RPMSG_ADDR_ANY;
+	chinfo.dst = le32_to_cpu(msg->addr);
+
+	dev_info(dev, "%sing channel %s addr 0x%x\n",
+		 (flags & RPMSG_NS_DESTROY) ? "destroy" : "creat",
+		 msg->name, chinfo.dst);
+
+	if (flags & RPMSG_NS_DESTROY) {
+		ret = rpmsg_release_channel(rpdev, &chinfo);
+		if (ret)
+			dev_err(dev, "rpmsg_destroy_channel failed: %d\n", ret);
+	} else {
+		newch = rpmsg_create_channel(rpdev, &chinfo);
+		if (!newch)
+			dev_err(dev, "rpmsg_create_channel failed\n");
+	}
+
+	return 0;
+}
+
+static int rpmsg_ns_probe(struct rpmsg_device *rpdev)
+{
+	struct rpmsg_channel_info ns_chinfo;
+	struct rpmsg_endpoint *ns_ept;
+
+	ns_chinfo.src = RPMSG_NS_ADDR;
+	ns_chinfo.dst = RPMSG_NS_ADDR;
+	strcpy(ns_chinfo.name, "name_service");
+
+	/*
+	 * Create the NS announcement service endpoint associated to the RPMsg
+	 * device. The endpoint will be automatically destroyed when the RPMsg
+	 * device will be deleted.
+	 */
+	ns_ept = rpmsg_create_ept(rpdev, rpmsg_ns_cb, NULL, ns_chinfo);
+	if (!ns_ept) {
+		dev_err(&rpdev->dev, "failed to create the ns ept\n");
+		return -ENOMEM;
+	}
+	rpdev->ept = ns_ept;
+
+	return 0;
+}
+
+static struct rpmsg_driver rpmsg_ns_driver = {
+	.drv.name = "rpmsg_ns",
+	.probe = rpmsg_ns_probe,
+};
+
+static int rpmsg_ns_init(void)
+{
+	int ret;
+
+	ret = register_rpmsg_driver(&rpmsg_ns_driver);
+	if (ret < 0)
+		pr_err("%s: Failed to register rpmsg driver\n", __func__);
+
+	return ret;
+}
+postcore_initcall(rpmsg_ns_init);
+
+static void rpmsg_ns_exit(void)
+{
+	unregister_rpmsg_driver(&rpmsg_ns_driver);
+}
+module_exit(rpmsg_ns_exit);
+
+MODULE_DESCRIPTION("Name service announcement rpmsg Driver");
+MODULE_AUTHOR("Arnaud Pouliquen <arnaud.pouliquen@st.com>");
+MODULE_ALIAS("rpmsg_ns");
+MODULE_LICENSE("GPL v2");
-- 
2.17.1