[PATCH v3] watchdog: add driver for StreamLabs USB watchdog device

[Alexey Klimov <klimov.linux@gmail.com>]

This patch creates new driver that supports StreamLabs usb watchdog
device. This device plugs into 9-pin usb header and connects to
reset pin and reset button on common PC.

USB commands used to communicate with device were reverse
engineered using usbmon.

Signed-off-by: Alexey Klimov <klimov.linux@gmail.com>
---

Changes in v3:
 -- coding style cleanups and rebase;
 -- buffer is allocated with separate allocation;
 -- adding comments about max/min limits;
 -- rework start/stop commands implementation;
 -- fix first if-check in probe() function;

Previous version: https://www.spinics.net/lists/linux-watchdog/msg09092.html

 drivers/watchdog/Kconfig          |  16 ++
 drivers/watchdog/Makefile         |   1 +
 drivers/watchdog/streamlabs_wdt.c | 321 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 338 insertions(+)
 create mode 100644 drivers/watchdog/streamlabs_wdt.c

diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index acb00b53a520..6a2195d8cc5c 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -1852,6 +1852,22 @@ config USBPCWATCHDOG
 
 	  Most people will say N.
 
+config USB_STREAMLABS_WATCHDOG
+	tristate "StreamLabs USB watchdog driver"
+	depends on USB
+	---help---
+	  This is the driver for the USB Watchdog dongle from StreamLabs.
+	  If you correctly connect reset pins to motherboard Reset pin and
+	  to Reset button then this device will simply watch your kernel to make
+	  sure it doesn't freeze, and if it does, it reboots your computer
+	  after a certain amount of time.
+
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called streamlabs_wdt.
+
+	  Most people will say N. Say yes or M if you want to use such usb device.
+
 comment "Watchdog Pretimeout Governors"
 
 config WATCHDOG_PRETIMEOUT_GOV
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index 0c3d35e3c334..d4a61222ccd2 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -31,6 +31,7 @@ obj-$(CONFIG_WDTPCI) += wdt_pci.o
 
 # USB-based Watchdog Cards
 obj-$(CONFIG_USBPCWATCHDOG) += pcwd_usb.o
+obj-$(CONFIG_USB_STREAMLABS_WATCHDOG) += streamlabs_wdt.o
 
 # ALPHA Architecture
 
diff --git a/drivers/watchdog/streamlabs_wdt.c b/drivers/watchdog/streamlabs_wdt.c
new file mode 100644
index 000000000000..4442d053d9f7
--- /dev/null
+++ b/drivers/watchdog/streamlabs_wdt.c
@@ -0,0 +1,321 @@
+/*
+ * StreamLabs USB Watchdog driver
+ *
+ * Copyright (c) 2016-2017 Alexey Klimov <klimov.linux@gmail.com>
+ *
+ * This program is free software; you may redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/usb.h>
+#include <linux/watchdog.h>
+#include <asm/byteorder.h>
+
+/*
+ * USB Watchdog device from Streamlabs:
+ * https://www.stream-labs.com/en/catalog/?cat_id=1203&item_id=323
+ *
+ * USB commands have been reverse engineered using usbmon.
+ */
+
+#define DRIVER_AUTHOR "Alexey Klimov <klimov.linux@gmail.com>"
+#define DRIVER_DESC "StreamLabs USB watchdog driver"
+#define DRIVER_NAME "usb_streamlabs_wdt"
+
+MODULE_AUTHOR(DRIVER_AUTHOR);
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL");
+
+#define USB_STREAMLABS_WATCHDOG_VENDOR	0x13c0
+#define USB_STREAMLABS_WATCHDOG_PRODUCT	0x0011
+
+/*
+ * one buffer is used for communication, however transmitted message is only
+ * 32 bytes long
+ */
+#define BUFFER_TRANSFER_LENGTH	32
+#define BUFFER_LENGTH		64
+#define USB_TIMEOUT		350
+
+#define STREAMLABS_CMD_START	0xaacc
+#define STREAMLABS_CMD_STOP	0xbbff
+
+/* timeouts values are taken from windows program */
+#define STREAMLABS_WDT_MIN_TIMEOUT	1
+#define STREAMLABS_WDT_MAX_TIMEOUT	46
+
+struct streamlabs_wdt {
+	struct watchdog_device wdt_dev;
+	struct usb_interface *intf;
+
+	struct mutex lock;
+	u8 *buffer;
+};
+
+static bool nowayout = WATCHDOG_NOWAYOUT;
+
+/*
+ * This function is used to check if watchdog actually changed
+ * its state to disabled that is reported in first two bytes of response
+ * message.
+ */
+static int usb_streamlabs_wdt_check_stop(u16 *buf)
+{
+	if (buf[0] != cpu_to_le16(STREAMLABS_CMD_STOP))
+		return -EINVAL;
+
+	return 0;
+}
+
+static int usb_streamlabs_wdt_validate_response(u8 *buf)
+{
+	/*
+	 * If watchdog device understood the command it will acknowledge
+	 * with values 1,2,3,4 at indexes 10, 11, 12, 13 in response message
+	 * when response treated as 8bit message.
+	 */
+	if (buf[10] != 1 || buf[11] != 2 || buf[12] != 3 || buf[13] != 4)
+		return -EINVAL;
+
+	return 0;
+}
+
+static void usb_streamlabs_wdt_prepare_buf(u16 *buf, u16 cmd,
+						unsigned long timeout_msec)
+{
+	/*
+	 * remaining elements expected to be zero everytime during
+	 * communication
+	 */
+	buf[0] = cpu_to_le16(cmd);
+	buf[1] = cpu_to_le16(0x8000);
+	buf[3] = cpu_to_le16(timeout_msec);
+	buf[5] = 0x0;
+	buf[6] = 0x0;
+}
+
+static int usb_streamlabs_wdt_cmd(struct streamlabs_wdt *wdt, u16 cmd)
+{
+	struct usb_device *usbdev;
+	unsigned long timeout_msec;
+	int retval;
+	int size;
+
+	if (unlikely(!wdt->intf))
+		return -ENODEV;
+
+	usbdev = interface_to_usbdev(wdt->intf);
+	timeout_msec = wdt->wdt_dev.timeout * MSEC_PER_SEC;
+
+	usb_streamlabs_wdt_prepare_buf((u16 *) wdt->buffer, cmd, timeout_msec);
+
+	/* send command to watchdog */
+	retval = usb_interrupt_msg(usbdev, usb_sndintpipe(usbdev, 0x02),
+					wdt->buffer, BUFFER_TRANSFER_LENGTH,
+					&size, USB_TIMEOUT);
+	if (retval)
+		return retval;
+
+	if (size != BUFFER_TRANSFER_LENGTH)
+		return -EIO;
+
+	/* and read response from watchdog */
+	retval = usb_interrupt_msg(usbdev, usb_rcvintpipe(usbdev, 0x81),
+					wdt->buffer, BUFFER_LENGTH,
+					&size, USB_TIMEOUT);
+	if (retval)
+		return retval;
+
+	if (size != BUFFER_LENGTH)
+		return -EIO;
+
+	/* check if watchdog actually acked/recognized command */
+	return usb_streamlabs_wdt_validate_response(wdt->buffer);
+}
+
+static int usb_streamlabs_wdt_stop_cmd(struct streamlabs_wdt *wdt)
+{
+	int retry_counter = 10; /* how many times to re-send stop cmd */
+	int retval;
+
+	/*
+	 * Transition from enabled to disabled state in this device
+	 * for stop command doesn't happen immediately. Usually, 2 or 3
+	 * (sometimes even 4) stop commands should be sent until
+	 * watchdog answers 'I'm stopped!'.
+	 * Retry only stop command if watchdog fails to answer correctly
+	 * about its state. After 10 attempts go out and return error.
+	 */
+
+	do {
+		retval = usb_streamlabs_wdt_cmd(wdt, STREAMLABS_CMD_STOP);
+		if (retval)
+			break;
+
+		retval = usb_streamlabs_wdt_check_stop((u16 *) wdt->buffer);
+
+	} while (retval && --retry_counter >= 0);
+
+	return retry_counter > 0 ? retval : -EIO;
+}
+
+static int usb_streamlabs_wdt_start(struct watchdog_device *wdt_dev)
+{
+	struct streamlabs_wdt *streamlabs_wdt = watchdog_get_drvdata(wdt_dev);
+	int retval;
+
+	mutex_lock(&streamlabs_wdt->lock);
+	retval = usb_streamlabs_wdt_cmd(streamlabs_wdt, STREAMLABS_CMD_START);
+	mutex_unlock(&streamlabs_wdt->lock);
+
+	return retval;
+}
+
+static int usb_streamlabs_wdt_stop(struct watchdog_device *wdt_dev)
+{
+	struct streamlabs_wdt *streamlabs_wdt = watchdog_get_drvdata(wdt_dev);
+	int retval;
+
+	mutex_lock(&streamlabs_wdt->lock);
+	retval = usb_streamlabs_wdt_stop_cmd(streamlabs_wdt);
+	mutex_unlock(&streamlabs_wdt->lock);
+
+	return retval;
+}
+
+static const struct watchdog_info streamlabs_wdt_ident = {
+	.options	= WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
+	.identity	= DRIVER_NAME,
+};
+
+static struct watchdog_ops usb_streamlabs_wdt_ops = {
+	.owner	= THIS_MODULE,
+	.start	= usb_streamlabs_wdt_start,
+	.stop	= usb_streamlabs_wdt_stop,
+};
+
+static int usb_streamlabs_wdt_probe(struct usb_interface *intf,
+					const struct usb_device_id *id)
+{
+	struct usb_device *usbdev = interface_to_usbdev(intf);
+	struct streamlabs_wdt *streamlabs_wdt;
+	int retval;
+
+	/*
+	 * USB IDs of this device appear to be weird/unregistered. Hence, do
+	 * an additional check on product and manufacturer.
+	 * If there is similar device in the field with same values then
+	 * there is stop command in probe() below that checks if the device
+	 * behaves as a watchdog.
+	 */
+	if (!usbdev->product || !usbdev->manufacturer
+		|| strncmp(usbdev->product, "USBkit", 6)
+		|| strncmp(usbdev->manufacturer, "STREAM LABS", 11))
+		return -ENODEV;
+
+	streamlabs_wdt = devm_kzalloc(&intf->dev, sizeof(struct streamlabs_wdt),
+								GFP_KERNEL);
+	if (!streamlabs_wdt)
+		return -ENOMEM;
+
+	streamlabs_wdt->buffer = kzalloc(BUFFER_LENGTH, GFP_KERNEL);
+	if (!streamlabs_wdt->buffer)
+		return -ENOMEM;
+
+	mutex_init(&streamlabs_wdt->lock);
+
+	streamlabs_wdt->wdt_dev.info = &streamlabs_wdt_ident;
+	streamlabs_wdt->wdt_dev.ops = &usb_streamlabs_wdt_ops;
+	streamlabs_wdt->wdt_dev.timeout = STREAMLABS_WDT_MAX_TIMEOUT;
+	streamlabs_wdt->wdt_dev.max_timeout = STREAMLABS_WDT_MAX_TIMEOUT;
+	streamlabs_wdt->wdt_dev.min_timeout = STREAMLABS_WDT_MIN_TIMEOUT;
+	streamlabs_wdt->wdt_dev.parent = &intf->dev;
+
+	streamlabs_wdt->intf = intf;
+	usb_set_intfdata(intf, &streamlabs_wdt->wdt_dev);
+	watchdog_set_drvdata(&streamlabs_wdt->wdt_dev, streamlabs_wdt);
+	watchdog_set_nowayout(&streamlabs_wdt->wdt_dev, nowayout);
+
+	retval = usb_streamlabs_wdt_stop(&streamlabs_wdt->wdt_dev);
+	if (retval)
+		goto free_buf;
+
+	retval = watchdog_register_device(&streamlabs_wdt->wdt_dev);
+	if (retval) {
+		dev_err(&intf->dev, "failed to register watchdog device\n");
+		goto free_buf;
+	}
+
+	dev_info(&intf->dev, "StreamLabs USB watchdog loaded.\n");
+	return 0;
+
+free_buf:
+	kfree(streamlabs_wdt->buffer);
+	return retval;
+}
+
+static int usb_streamlabs_wdt_suspend(struct usb_interface *intf,
+					pm_message_t message)
+{
+	struct streamlabs_wdt *streamlabs_wdt = usb_get_intfdata(intf);
+
+	if (watchdog_active(&streamlabs_wdt->wdt_dev))
+		return usb_streamlabs_wdt_stop(&streamlabs_wdt->wdt_dev);
+
+	return 0;
+}
+
+static int usb_streamlabs_wdt_resume(struct usb_interface *intf)
+{
+	struct streamlabs_wdt *streamlabs_wdt = usb_get_intfdata(intf);
+
+	if (watchdog_active(&streamlabs_wdt->wdt_dev))
+		return usb_streamlabs_wdt_start(&streamlabs_wdt->wdt_dev);
+
+	return 0;
+}
+
+static void usb_streamlabs_wdt_disconnect(struct usb_interface *intf)
+{
+	struct streamlabs_wdt *streamlabs_wdt = usb_get_intfdata(intf);
+
+	mutex_lock(&streamlabs_wdt->lock);
+	usb_streamlabs_wdt_stop_cmd(streamlabs_wdt);
+	usb_set_intfdata(intf, NULL);
+	streamlabs_wdt->intf = NULL;
+	mutex_unlock(&streamlabs_wdt->lock);
+
+	watchdog_unregister_device(&streamlabs_wdt->wdt_dev);
+}
+
+static struct usb_device_id usb_streamlabs_wdt_device_table[] = {
+	{ USB_DEVICE(USB_STREAMLABS_WATCHDOG_VENDOR, USB_STREAMLABS_WATCHDOG_PRODUCT) },
+	{ }	/* Terminating entry */
+};
+
+MODULE_DEVICE_TABLE(usb, usb_streamlabs_wdt_device_table);
+
+static struct usb_driver usb_streamlabs_wdt_driver = {
+	.name		= DRIVER_NAME,
+	.probe		= usb_streamlabs_wdt_probe,
+	.disconnect	= usb_streamlabs_wdt_disconnect,
+	.suspend	= usb_streamlabs_wdt_suspend,
+	.resume		= usb_streamlabs_wdt_resume,
+	.reset_resume	= usb_streamlabs_wdt_resume,
+	.id_table	= usb_streamlabs_wdt_device_table,
+};
+
+module_usb_driver(usb_streamlabs_wdt_driver);
-- 
2.11.0