@@ -17,6 +17,13 @@ config LORA_DEV
 
 if LORA_DEV
 
+config LORA_RAK811
+	tristate "RAK RAK811 driver"
+	default y
+	depends on SERIAL_DEV_BUS
+	help
+	  RAK RAK811/RAK812
+
 config LORA_RN2483
 	tristate "Microchip RN2483/RN2903 driver"
 	default y

@@ -9,6 +9,9 @@ lora-dev-y := dev.o
 # Alphabetically sorted.
 #
 
+obj-$(CONFIG_LORA_RAK811) += lora-rak811.o
+lora-rak811-y := rak811.o
+
 obj-$(CONFIG_LORA_RN2483) += lora-rn2483.o
 lora-rn2483-y := rn2483.o
 lora-rn2483-y += rn2483_cmd.o

@@ -0,0 +1,219 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * RAK RAK811
+ *
+ * Copyright (c) 2017-2018 Andreas F?rber
+ */
+
+#include <linux/delay.h>
+#include <linux/lora.h>
+#include <linux/module.h>
+#include <linux/netdevice.h>
+#include <linux/of.h>
+#include <linux/serdev.h>
+#include <linux/lora/dev.h>
+
+struct rak811_device {
+	struct serdev_device *serdev;
+
+	char rx_buf[4096];
+	int rx_len;
+
+	struct completion line_recv_comp;
+};
+
+static int rak811_send_command(struct rak811_device *rakdev, const char *cmd, char **data, unsigned long timeout)
+{
+	struct serdev_device *sdev = rakdev->serdev;
+	const char *crlf = "\r\n";
+	char *resp;
+
+	serdev_device_write_buf(sdev, cmd, strlen(cmd));
+	serdev_device_write_buf(sdev, crlf, 2);
+
+	timeout = wait_for_completion_timeout(&rakdev->line_recv_comp, timeout);
+	if (!timeout)
+		return -ETIMEDOUT;
+
+	resp = rakdev->rx_buf;
+	dev_dbg(&sdev->dev, "Received: '%s'\n", resp);
+	if (data)
+		*data = kstrdup(resp, GFP_KERNEL);
+
+	rakdev->rx_len = 0;
+	reinit_completion(&rakdev->line_recv_comp);
+
+	return 0;
+}
+
+static int rak811_simple_cmd(struct rak811_device *rakdev, const char *cmd, unsigned long timeout)
+{
+	char *resp;
+	int ret;
+
+	ret = rak811_send_command(rakdev, cmd, &resp, timeout);
+	if (ret)
+		return ret;
+
+	if (strncmp(resp, "OK", 2) == 0) {
+		kfree(resp);
+		return 0;
+	}
+
+	kfree(resp);
+
+	return -EINVAL;
+}
+
+static int rak811_get_version(struct rak811_device *rakdev, char **version, unsigned long timeout)
+{
+	char *resp;
+	int ret;
+
+	ret = rak811_send_command(rakdev, "at+version", &resp, timeout);
+	if (ret)
+		return ret;
+
+	if (strncmp(resp, "OK", 2) == 0) {
+		*version = kstrdup(resp + 2, GFP_KERNEL);
+		kfree(resp);
+		return 0;
+	}
+
+	kfree(resp);
+
+	return -EINVAL;
+}
+
+static int rak811_receive_buf(struct serdev_device *sdev, const u8 *data, size_t count)
+{
+	struct rak811_device *rakdev = serdev_device_get_drvdata(sdev);
+	size_t i = 0;
+	int len = 0;
+
+	dev_dbg(&sdev->dev, "Receive (%d)\n", (int)count);
+
+	for (i = 0; i < count; i++) {
+		dev_dbg(&sdev->dev, "Receive: 0x%02x\n", (int)data[i]);
+	}
+
+	if (completion_done(&rakdev->line_recv_comp)) {
+		dev_info(&sdev->dev, "RX waiting on completion\n");
+		return 0;
+	}
+	if (rakdev->rx_len == sizeof(rakdev->rx_buf) - 1) {
+		dev_warn(&sdev->dev, "RX buffer full\n");
+		return 0;
+	}
+
+	i = min(count, sizeof(rakdev->rx_buf) - 1 - rakdev->rx_len);
+	if (i > 0) {
+		memcpy(&rakdev->rx_buf[rakdev->rx_len], data, i);
+		rakdev->rx_len += i;
+		len += i;
+	}
+	if (rakdev->rx_len >= 2 && strncmp(&rakdev->rx_buf[rakdev->rx_len - 2], "\r\n", 2) == 0) {
+		rakdev->rx_len -= 2;
+		rakdev->rx_buf[rakdev->rx_len] = '\0';
+		complete(&rakdev->line_recv_comp);
+	}
+
+	return len;
+}
+
+static const struct serdev_device_ops rak811_serdev_client_ops = {
+	.receive_buf = rak811_receive_buf,
+};
+
+static int rak811_probe(struct serdev_device *sdev)
+{
+	struct rak811_device *rakdev;
+	char *sz;
+	int ret;
+
+	dev_info(&sdev->dev, "Probing\n");
+
+	rakdev = devm_kzalloc(&sdev->dev, sizeof(struct rak811_device), GFP_KERNEL);
+	if (!rakdev)
+		return -ENOMEM;
+
+	rakdev->serdev = sdev;
+	init_completion(&rakdev->line_recv_comp);
+	serdev_device_set_drvdata(sdev, rakdev);
+
+	ret = serdev_device_open(sdev);
+	if (ret) {
+		dev_err(&sdev->dev, "Failed to open (%d)\n", ret);
+		return ret;
+	}
+
+	serdev_device_set_baudrate(sdev, 115200);
+	serdev_device_set_flow_control(sdev, false);
+	serdev_device_set_client_ops(sdev, &rak811_serdev_client_ops);
+
+	ret = rak811_get_version(rakdev, &sz, HZ);
+	if (ret) {
+		dev_err(&sdev->dev, "Failed to get version (%d)\n", ret);
+		serdev_device_close(sdev);
+		return ret;
+	}
+
+	dev_info(&sdev->dev, "firmware version: %s\n", sz);
+	kfree(sz);
+
+	ret = rak811_simple_cmd(rakdev, "at+mode=1", 2 * HZ);
+	if (ret) {
+		dev_err(&sdev->dev, "Failed to set mode to P2P (%d)\n", ret);
+		serdev_device_close(sdev);
+		return ret;
+	}
+
+	dev_info(&sdev->dev, "Done.\n");
+
+	return 0;
+}
+
+static void rak811_remove(struct serdev_device *sdev)
+{
+	serdev_device_close(sdev);
+
+	dev_info(&sdev->dev, "Removed\n");
+}
+
+static const struct of_device_id rak811_of_match[] = {
+	{ .compatible = "rakwireless,rak811" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, rak811_of_match);
+
+static struct serdev_device_driver rak811_serdev_driver = {
+	.probe = rak811_probe,
+	.remove = rak811_remove,
+	.driver = {
+		.name = "rak811",
+		.of_match_table = rak811_of_match,
+	},
+};
+
+static int __init rak811_init(void)
+{
+	int ret;
+
+	ret = serdev_device_driver_register(&rak811_serdev_driver);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static void __exit rak811_exit(void)
+{
+	serdev_device_driver_unregister(&rak811_serdev_driver);
+}
+
+module_init(rak811_init);
+module_exit(rak811_exit);
+
+MODULE_DESCRIPTION("RAK811 serdev driver");
+MODULE_AUTHOR("Andreas F?rber <afaerber@suse.de>");
+MODULE_LICENSE("GPL");