[PATCH net-next v2 4/8] net: rpmsg-eth: Add basic rpmsg skeleton

[MD Danish Anwar <danishanwar@ti.com>]

Introduces a basic RPMSG Ethernet driver and add it's basic skeleton.
Add support for creating virtual Ethernet devices over RPMSG channels,
allowing user-space programs to send and receive messages using a
standard Ethernet protocol. The driver includes message handling,
probe, and remove functions, along with necessary data structures.

Signed-off-by: MD Danish Anwar <danishanwar@ti.com>
---
 drivers/net/ethernet/Kconfig     |  10 +++
 drivers/net/ethernet/Makefile    |   1 +
 drivers/net/ethernet/rpmsg_eth.c | 142 +++++++++++++++++++++++++++++++
 drivers/net/ethernet/rpmsg_eth.h |  75 ++++++++++++++++
 4 files changed, 228 insertions(+)
 create mode 100644 drivers/net/ethernet/rpmsg_eth.c
 create mode 100644 drivers/net/ethernet/rpmsg_eth.h

diff --git a/drivers/net/ethernet/Kconfig b/drivers/net/ethernet/Kconfig
index f86d4557d8d7..a73a45a9ef3d 100644
--- a/drivers/net/ethernet/Kconfig
+++ b/drivers/net/ethernet/Kconfig
@@ -170,6 +170,16 @@ config OA_TC6
 	  To know the implementation details, refer documentation in
 	  <file:Documentation/networking/oa-tc6-framework.rst>.
 
+config RPMSG_ETH
+	tristate "RPMsg Based Virtual Ethernet driver"
+	depends on RPMSG
+	help
+	  This makes it possible for user-space programs to send and receive
+	  rpmsg messages as a standard eth protocol.
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called rpmsg_eth.
+
 source "drivers/net/ethernet/packetengines/Kconfig"
 source "drivers/net/ethernet/pasemi/Kconfig"
 source "drivers/net/ethernet/pensando/Kconfig"
diff --git a/drivers/net/ethernet/Makefile b/drivers/net/ethernet/Makefile
index 67182339469a..aebd15993e3c 100644
--- a/drivers/net/ethernet/Makefile
+++ b/drivers/net/ethernet/Makefile
@@ -107,3 +107,4 @@ obj-$(CONFIG_NET_VENDOR_XIRCOM) += xircom/
 obj-$(CONFIG_NET_VENDOR_SYNOPSYS) += synopsys/
 obj-$(CONFIG_NET_VENDOR_PENSANDO) += pensando/
 obj-$(CONFIG_OA_TC6) += oa_tc6.o
+obj-$(CONFIG_RPMSG_ETH) += rpmsg_eth.o
diff --git a/drivers/net/ethernet/rpmsg_eth.c b/drivers/net/ethernet/rpmsg_eth.c
new file mode 100644
index 000000000000..4cfd9ff2f142
--- /dev/null
+++ b/drivers/net/ethernet/rpmsg_eth.c
@@ -0,0 +1,142 @@
+// SPDX-License-Identifier: GPL-2.0
+/* RPMsg Based Virtual Ethernet Driver
+ *
+ * Copyright (C) 2025 Texas Instruments Incorporated - https://www.ti.com/
+ */
+
+#include <linux/of.h>
+#include <linux/of_reserved_mem.h>
+#include <linux/remoteproc.h>
+#include "rpmsg_eth.h"
+
+static int rpmsg_eth_rpmsg_cb(struct rpmsg_device *rpdev, void *data, int len,
+			      void *priv, u32 src)
+{
+	struct rpmsg_eth_common *common = dev_get_drvdata(&rpdev->dev);
+	struct message *msg = (struct message *)data;
+	u32 msg_type = msg->msg_hdr.msg_type;
+	int ret = 0;
+
+	switch (msg_type) {
+	case RPMSG_ETH_REQUEST_MSG:
+	case RPMSG_ETH_RESPONSE_MSG:
+	case RPMSG_ETH_NOTIFY_MSG:
+		dev_dbg(common->dev, "Msg type = %d, Src Id = %d\n",
+			msg_type, msg->msg_hdr.src_id);
+		break;
+	default:
+		dev_err(common->dev, "Invalid msg type\n");
+		ret = -EINVAL;
+		break;
+	}
+	return ret;
+}
+
+/**
+ * rpmsg_eth_get_shm_info - Retrieve shared memory region for RPMsg Ethernet
+ * @common: Pointer to rpmsg_eth_common structure
+ *
+ * This function locates and maps the reserved memory region for the RPMsg
+ * Ethernet device by traversing the device tree hierarchy. It first identifies
+ * the associated remote processor (rproc), then locates the "rpmsg-eth" child
+ * node within the rproc's device tree node, and finally retrieves the
+ * "memory-region" phandle that points to the reserved memory region.
+ * Once found, the shared memory region is mapped into the
+ * kernel's virtual address space using devm_ioremap()
+ *
+ * Return: 0 on success, negative error code on failure.
+ */
+static int rpmsg_eth_get_shm_info(struct rpmsg_eth_common *common)
+{
+	struct device_node *np, *rpmsg_eth_node, *rmem_np;
+	struct reserved_mem *rmem;
+	struct rproc *rproc;
+
+	/* Get the remote processor associated with this device */
+	rproc = rproc_get_by_child(&common->rpdev->dev);
+	if (!rproc) {
+		dev_err(common->dev, "rpmsg eth device not child of rproc\n");
+		return -EINVAL;
+	}
+
+	/* Get the device node from rproc or its parent */
+	np = rproc->dev.of_node ?: (rproc->dev.parent ? rproc->dev.parent->of_node : NULL);
+	if (!np) {
+		dev_err(common->dev, "Cannot find rproc device node\n");
+		return -ENODEV;
+	}
+
+	/* Get the rpmsg-eth child node */
+	rpmsg_eth_node = of_get_child_by_name(np, "rpmsg-eth");
+	if (!rpmsg_eth_node) {
+		dev_err(common->dev, "Couldn't get rpmsg-eth node from np\n");
+		return -ENODEV;
+	}
+
+	/* Parse the memory-region phandle */
+	rmem_np = of_parse_phandle(rpmsg_eth_node, "memory-region", 0);
+	of_node_put(rpmsg_eth_node);
+	if (!rmem_np)
+		return -EINVAL;
+
+	/* Lookup the reserved memory region */
+	rmem = of_reserved_mem_lookup(rmem_np);
+	of_node_put(rmem_np);
+	if (!rmem)
+		return -EINVAL;
+
+	common->port->shm = devm_ioremap(common->dev, rmem->base, rmem->size);
+	if (IS_ERR(common->port->shm))
+		return PTR_ERR(common->port->shm);
+
+	common->port->buf_size = rmem->size;
+
+	return 0;
+}
+
+static int rpmsg_eth_probe(struct rpmsg_device *rpdev)
+{
+	struct device *dev = &rpdev->dev;
+	struct rpmsg_eth_common *common;
+	int ret = 0;
+
+	common = devm_kzalloc(&rpdev->dev, sizeof(*common), GFP_KERNEL);
+	if (!common)
+		return -ENOMEM;
+
+	dev_set_drvdata(dev, common);
+
+	common->port = devm_kzalloc(dev, sizeof(*common->port), GFP_KERNEL);
+	common->dev = dev;
+	common->rpdev = rpdev;
+
+	ret = rpmsg_eth_get_shm_info(common);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static void rpmsg_eth_remove(struct rpmsg_device *rpdev)
+{
+	dev_dbg(&rpdev->dev, "rpmsg-eth client driver is removed\n");
+}
+
+static struct rpmsg_device_id rpmsg_eth_rpmsg_id_table[] = {
+	{ .name = "shm-eth" },
+	{},
+};
+MODULE_DEVICE_TABLE(rpmsg, rpmsg_eth_rpmsg_id_table);
+
+static struct rpmsg_driver rpmsg_eth_rpmsg_client = {
+	.drv.name = KBUILD_MODNAME,
+	.id_table = rpmsg_eth_rpmsg_id_table,
+	.probe = rpmsg_eth_probe,
+	.callback = rpmsg_eth_rpmsg_cb,
+	.remove = rpmsg_eth_remove,
+};
+module_rpmsg_driver(rpmsg_eth_rpmsg_client);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("MD Danish Anwar <danishanwar@ti.com>");
+MODULE_DESCRIPTION("RPMsg Based Virtual Ethernet driver");
diff --git a/drivers/net/ethernet/rpmsg_eth.h b/drivers/net/ethernet/rpmsg_eth.h
new file mode 100644
index 000000000000..12be1c35eff8
--- /dev/null
+++ b/drivers/net/ethernet/rpmsg_eth.h
@@ -0,0 +1,75 @@
+/* SPDX-License-Identifier: GPL-2.0
+ * RPMsg Based Virtual Ethernet Driver common header
+ *
+ * Copyright (C) 2025 Texas Instruments Incorporated - https://www.ti.com/
+ */
+
+#ifndef __RPMSG_ETH_H__
+#define __RPMSG_ETH_H__
+
+#include <linux/errno.h>
+#include <linux/etherdevice.h>
+#include <linux/if_ether.h>
+#include <linux/if_vlan.h>
+#include <linux/jiffies.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/netdevice.h>
+#include <linux/rpmsg.h>
+
+#define RPMSG_ETH_SHM_MAGIC_NUM 0xABCDABCD
+
+enum rpmsg_eth_msg_type {
+	RPMSG_ETH_REQUEST_MSG = 0,
+	RPMSG_ETH_RESPONSE_MSG,
+	RPMSG_ETH_NOTIFY_MSG,
+};
+
+/**
+ * struct message_header - message header structure for RPMSG Ethernet
+ * @src_id: Source endpoint ID
+ * @msg_type: Message type
+ */
+struct message_header {
+	u32 src_id;
+	u32 msg_type;
+} __packed;
+
+/**
+ * struct message - RPMSG Ethernet message structure
+ *
+ * @msg_hdr: Message header contains source and destination endpoint and
+ *          the type of message
+ *
+ * This structure is used to send and receive messages between the RPMSG
+ * Ethernet ports.
+ */
+struct message {
+	struct message_header msg_hdr;
+} __packed;
+
+/**
+ * struct rpmsg_eth_common - common structure for RPMSG Ethernet
+ * @rpdev: RPMSG device
+ * @port: Ethernet port
+ * @dev: Device
+ */
+struct rpmsg_eth_common {
+	struct rpmsg_device *rpdev;
+	struct rpmsg_eth_port *port;
+	struct device *dev;
+};
+
+/**
+ * struct rpmsg_eth_port - Ethernet port structure for RPMSG Ethernet
+ * @common: Pointer to the common RPMSG Ethernet structure
+ * @shm: Shared memory region mapping
+ * @buf_size: Size (in bytes) of the shared memory buffer for this port
+ */
+struct rpmsg_eth_port {
+	struct rpmsg_eth_common *common;
+	void __iomem *shm;
+	phys_addr_t buf_size;
+};
+
+#endif /* __RPMSG_ETH_H__ */
-- 
2.34.1