[PATCH v2] 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 v2:
 -- coding style cleanups
 -- turn some dev_err messages to dev_dbg
 -- reimplemented usb_streamlabs_wdt_command() to use loop
 -- re-worked disconnect routine
 -- rebased to 4.6-rc2, removed set_timeout method
 -- removed braces in .options field in streamlabs_wdt_indent
 -- mem allocation migrated to devm_kzalloc
 -- buffer for device struct moved inside main struct
    to avoid additional memory allocation
 -- removed watchdog_init_timeout()
 -- re-worked usb_streamlabs_wdt_{resume,suspend}
 -- removed struct usb_device pointer from main driver struct
 -- buffer preparation for communication migrated to cpu_to_le16()
    functions, also buffer is filled in as u16 elements to
    make this byteorder usable
 -- added stop command in usb_streamlabs_wdt_disconnect()
 
 drivers/watchdog/Kconfig          |  15 ++
 drivers/watchdog/Makefile         |   1 +
 drivers/watchdog/streamlabs_wdt.c | 313 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 329 insertions(+)
 create mode 100644 drivers/watchdog/streamlabs_wdt.c

diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index fb94765..130cf54 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -1766,4 +1766,19 @@ 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.
 endif # WATCHDOG
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index feb6270..9d36929 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -25,6 +25,7 @@ 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 0000000..3e34cd8
--- /dev/null
+++ b/drivers/watchdog/streamlabs_wdt.c
@@ -0,0 +1,313 @@
+/*
+ * StreamLabs USB Watchdog driver
+ *
+ * Copyright (c) 2016 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
+ * http://www.stream-labs.com/products/devices/watchdog/
+ *
+ * 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
+
+#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[BUFFER_LENGTH];
+};
+
+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_command(struct watchdog_device *wdt_dev, u16 cmd)
+{
+	struct streamlabs_wdt *streamlabs_wdt = watchdog_get_drvdata(wdt_dev);
+	struct usb_device *usbdev;
+	int retval;
+	int size;
+	unsigned long timeout_msec;
+
+	int retry_counter = 10;		/* how many times to re-send stop cmd */
+
+	mutex_lock(&streamlabs_wdt->lock);
+
+	if (unlikely(!streamlabs_wdt->intf)) {
+		mutex_unlock(&streamlabs_wdt->lock);
+		return -ENODEV;
+	}
+
+	usbdev = interface_to_usbdev(streamlabs_wdt->intf);
+	timeout_msec = wdt_dev->timeout * MSEC_PER_SEC;
+
+	do {
+		usb_streamlabs_wdt_prepare_buf((u16 *) streamlabs_wdt->buffer,
+							cmd, timeout_msec);
+		/* send command to watchdog */
+		retval = usb_interrupt_msg(usbdev, usb_sndintpipe(usbdev, 0x02),
+				streamlabs_wdt->buffer, BUFFER_TRANSFER_LENGTH,
+				&size, USB_TIMEOUT);
+
+		if (retval || size != BUFFER_TRANSFER_LENGTH) {
+			dev_dbg(&streamlabs_wdt->intf->dev,
+				"error %i when submitting interrupt msg\n",
+									retval);
+			retval = -EIO;
+			goto out;
+		}
+
+		/* and read response from watchdog */
+		retval = usb_interrupt_msg(usbdev, usb_rcvintpipe(usbdev, 0x81),
+				streamlabs_wdt->buffer, BUFFER_LENGTH,
+				&size, USB_TIMEOUT);
+
+		if (retval || size != BUFFER_LENGTH) {
+			dev_dbg(&streamlabs_wdt->intf->dev,
+				"error %i when receiving interrupt msg\n",
+									retval);
+			retval = -EIO;
+			goto out;
+		}
+
+		/* check if watchdog actually acked/recognized command */
+		retval = usb_streamlabs_wdt_validate_response(streamlabs_wdt->buffer);
+		if (retval) {
+			dev_dbg(&streamlabs_wdt->intf->dev,
+					"watchdog didn't ACK command!\n");
+			goto out;
+		}
+
+		/*
+		 * 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.
+		 * We do not retry start command.
+		 */
+	} while (cmd != STREAMLABS_CMD_START
+		&& usb_streamlabs_wdt_check_stop((u16 *) streamlabs_wdt->buffer)
+		&& --retry_counter >= 0);
+
+out:
+	mutex_unlock(&streamlabs_wdt->lock);
+	return retry_counter > 0 ? retval : -EIO;
+}
+
+static int usb_streamlabs_wdt_start(struct watchdog_device *wdt_dev)
+{
+	return usb_streamlabs_wdt_command(wdt_dev, STREAMLABS_CMD_START);
+}
+
+static int usb_streamlabs_wdt_stop(struct watchdog_device *wdt_dev)
+{
+	return usb_streamlabs_wdt_command(wdt_dev, STREAMLABS_CMD_STOP);
+}
+
+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) != 0
+		|| strncmp(usbdev->manufacturer, "STREAM LABS", 11) != 0))
+		return -ENODEV;
+
+	streamlabs_wdt = devm_kzalloc(&intf->dev, sizeof(struct streamlabs_wdt),
+								GFP_KERNEL);
+	if (!streamlabs_wdt)
+		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)
+		return retval;
+
+	retval = watchdog_register_device(&streamlabs_wdt->wdt_dev);
+	if (retval) {
+		dev_err(&intf->dev, "failed to register watchdog device\n");
+		return retval;
+	}
+
+	dev_info(&intf->dev, "StreamLabs USB watchdog loaded.\n");
+
+	return 0;
+}
+
+
+
+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);
+
+	usb_streamlabs_wdt_stop(&streamlabs_wdt->wdt_dev);
+
+	mutex_lock(&streamlabs_wdt->lock);
+	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);
-- 
2.8.0.rc3