Re: [PATCH v5] watchdog: add driver for StreamLabs USB watchdog device
From: Guenter Roeck
Date: Mon Jul 25 2022 - 10:03:05 EST
On 7/24/22 20:06, Alexey Klimov wrote:
Driver supports StreamLabs usb watchdog device. The device plugs
into 9-pin usb header and connects to reset pins and reset button
pins on desktop PC.
USB commands used to communicate with device were reverse
engineered using usbmon.
Signed-off-by: Alexey Klimov <klimov.linux@xxxxxxxxx>
---
Changes since v4:
-- added more comments;
-- added nowayout check in ->disconnect();
-- completely rework usb_streamlabs_wdt_cmd() ->
__usb_streamlabs_wdt_cmd() and functions
that handle validation of the response;
-- usb sending and receiving msgs are moved to separate
functions;
-- added soft_unbind=1 flag in usb_driver struct
to make it possible to send URBs in ->disconnect();
-- buffer is declared as __le16 now;
-- made checkpatch.pl --strict happy;
Previous version:
https://lore.kernel.org/linux-watchdog/20220715234442.3910204-1-klimov.linux@xxxxxxxxx/
MAINTAINERS | 6 +
drivers/watchdog/Kconfig | 15 ++
drivers/watchdog/Makefile | 1 +
drivers/watchdog/streamlabs_wdt.c | 360 ++++++++++++++++++++++++++++++
4 files changed, 382 insertions(+)
create mode 100644 drivers/watchdog/streamlabs_wdt.c
diff --git a/MAINTAINERS b/MAINTAINERS
index 64379c699903..fb31c1823043 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -19190,6 +19190,12 @@ W: http://www.stlinux.com
F: Documentation/networking/device_drivers/ethernet/stmicro/
F: drivers/net/ethernet/stmicro/stmmac/
+STREAMLABS USB WATCHDOG DRIVER
+M: Alexey Klimov <klimov.linux@xxxxxxxxx>
+L: linux-watchdog@xxxxxxxxxxxxxxx
+S: Maintained
+F: drivers/watchdog/streamlabs_wdt.c
+
SUN3/3X
M: Sam Creasey <sammy@xxxxxxxxx>
S: Maintained
diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 32fd37698932..64b7f947b196 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -2171,6 +2171,21 @@ 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.
+
config KEEMBAY_WATCHDOG
tristate "Intel Keem Bay SoC non-secure watchdog"
depends on ARCH_KEEMBAY || (ARM64 && COMPILE_TEST)
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index c324e9d820e9..2d601da9b5bd 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -33,6 +33,7 @@ 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..f1130fe5559c
--- /dev/null
+++ b/drivers/watchdog/streamlabs_wdt.c
@@ -0,0 +1,360 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * StreamLabs USB Watchdog driver
+ *
+ * Copyright (c) 2016-2017,2022 Alexey Klimov <klimov.linux@xxxxxxxxx>
+ */
+
+#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/products/devices/watch-dog/
+ *
+ * USB commands have been reverse engineered using usbmon.
+ */
+
+#define DRIVER_AUTHOR "Alexey Klimov <klimov.linux@xxxxxxxxx>"
+#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
+
Comment about the unit (ms) might be useful.
+#define STREAMLABS_CMD_START 0xaacc
+#define STREAMLABS_CMD_STOP 0xbbff
+
+/* timeout 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;
+ /* Serialises usb communication with a device */
+ struct mutex lock;
+ __le16 *buffer;
+};
+
+static bool nowayout = WATCHDOG_NOWAYOUT;
+module_param(nowayout, bool, 0);
+MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
+ __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
+
+/* USB call wrappers to send and receive messages to/from the device. */
+static int usb_streamlabs_send_msg(struct usb_device *usbdev, __le16 *buf)
+{
+ int retval;
+ int size;
+
+ retval = usb_interrupt_msg(usbdev, usb_sndintpipe(usbdev, 0x02),
+ buf, BUFFER_TRANSFER_LENGTH,
+ &size, USB_TIMEOUT);
+
+ if (size != BUFFER_TRANSFER_LENGTH)
+ return -EIO;
+
If usb_interrupt_msg() returns an error, it will likely not set size,
which may result in a random -EIO. I think this should be something like
if (retval)
return retval;
if (size != BUFFER_TRANSFER_LENGTH)
return -EIO;
return 0;
+ return retval;
+}
+
+static int usb_streamlabs_get_msg(struct usb_device *usbdev, __le16 *buf)
+{
+ int retval;
+ int size;
+
+ retval = usb_interrupt_msg(usbdev, usb_rcvintpipe(usbdev, 0x81),
+ buf, BUFFER_LENGTH,
+ &size, USB_TIMEOUT);
+
+ if (size != BUFFER_LENGTH)
+ return -EIO;
+
Same here.
+ return retval;
+}
+
+/*
+ * This function is used to check if watchdog timeout in the received buffer
+ * matches the timeout passed from watchdog subsystem.
+ */
+static int usb_streamlabs_wdt_check_timeout(__le16 *buf, unsigned long timeout)
+{
+ if (buf[3] != cpu_to_le16(timeout))
+ return -EPROTO;
+
+ return 0;
+}
+
+static int usb_streamlabs_wdt_check_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 -EPROTO;
+
+ return 0;
+}
+
+/*
+ * This function is used to check if watchdog command in the received buffer
+ * matches the command passed to the device.
+ */
+static int usb_streamlabs_wdt_check_command(__le16 *buf, u16 cmd)
+{
+ if (buf[0] != cpu_to_le16(cmd))
+ return -EPROTO;
+
+ return 0;
+}
+
+static int usb_streamlabs_wdt_validate_response(__le16 *buf, u16 cmd,
+ unsigned long timeout_msec)
+{
+ int retval;
+
+ retval = usb_streamlabs_wdt_check_response((u8 *)buf);
+ if (retval)
+ return retval;
+
+ retval = usb_streamlabs_wdt_check_command(buf, cmd);
+ if (retval)
+ return retval;
+
+ retval = usb_streamlabs_wdt_check_timeout(buf, timeout_msec);
+ return retval;
assignment to retval is unnecessary.
+}
+
+static void usb_streamlabs_wdt_prepare_buf(__le16 *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);
Not setting buf[2] and buf[4] contradicts the comment above. Maybe
those offsets are not _expected_ to be set by the device, but that
is not guaranteed. It may be safer to just use memset() at the
beginning of the function to clear the buffer.
+ 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;
+ /* how many times to re-try getting the state of the device */
+ unsigned int retry_counter = 10;
+ int retval;
+
+ 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(wdt->buffer, cmd, timeout_msec);
+
+ /* send command to watchdog */
+ retval = usb_streamlabs_send_msg(usbdev, wdt->buffer);
+ if (retval)
+ return retval;
+
+ /*
+ * Transition from one state to another in this device
+ * doesn't happen immediately, especially stopping the device
+ * is not observed on the first reading of the response.
+ * Plus to avoid potentially stale response message in the device
+ * we keep reading the state of the device until we see:
+ * -- that device recognised the sent command;
+ * -- the received state (started or stopped) matches the state
+ * that was requested;
+ * -- the timeout passed matches the timeout value read from
+ * the device.
+ * Keep retrying 10 times and if watchdog device doesn't respond
+ * correctly as expected we bail out and return an error.
+ */
+ do {
+ retval = usb_streamlabs_get_msg(usbdev, wdt->buffer);
+ if (retval)
+ break;
+
+ retval = usb_streamlabs_wdt_validate_response(wdt->buffer, cmd,
+ timeout_msec);
+ } while (retval && retry_counter--);
+
+ return retry_counter ? retval : -EIO;
+}
+
+static int usb_streamlabs_wdt_cmd(struct streamlabs_wdt *streamlabs_wdt, u16 cmd)
+{
+ int retval;
+
+ mutex_lock(&streamlabs_wdt->lock);
+ retval = __usb_streamlabs_wdt_cmd(streamlabs_wdt, cmd);
+ mutex_unlock(&streamlabs_wdt->lock);
+
+ return retval;
+}
+
+static int usb_streamlabs_wdt_start(struct watchdog_device *wdt_dev)
+{
+ struct streamlabs_wdt *streamlabs_wdt = watchdog_get_drvdata(wdt_dev);
+
+ return usb_streamlabs_wdt_cmd(streamlabs_wdt, STREAMLABS_CMD_START);
+}
+
+static int usb_streamlabs_wdt_stop(struct watchdog_device *wdt_dev)
+{
+ struct streamlabs_wdt *streamlabs_wdt = watchdog_get_drvdata(wdt_dev);
+
+ return usb_streamlabs_wdt_cmd(streamlabs_wdt, STREAMLABS_CMD_STOP);
+}
+
+static const struct watchdog_info streamlabs_wdt_ident = {
+ .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
+ .identity = DRIVER_NAME,
+};
+
+static const 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 = devm_kzalloc(&intf->dev, BUFFER_LENGTH,
+ GFP_KERNEL);
+ if (!streamlabs_wdt->buffer)
+ return -ENOMEM;
+
Nit: buffer could be made part of struct streamlabs_wdt and be tagged with
____cacheline_aligned to avoid the double allocation.
+ 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 -ENODEV;
+
A comment explaining why the watchdog is explicitly stopped when running
might be useful.
+ retval = devm_watchdog_register_device(&intf->dev,
+ &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 driver 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);
+
+ mutex_lock(&streamlabs_wdt->lock);
+ /*
+ * If disconnect happens via sysfs or on rmmod, then try to stop
+ * the watchdog. In case of physical detachment of the device this call
+ * will fail but we continue.
+ */
+ if (!nowayout)
+ __usb_streamlabs_wdt_cmd(streamlabs_wdt, STREAMLABS_CMD_STOP);
+ /* Stop sending (new) messages to the device */
+ streamlabs_wdt->intf = NULL;
+ mutex_unlock(&streamlabs_wdt->lock);
+}
+
+static const 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,
+ .soft_unbind = 1,
+};
+
+module_usb_driver(usb_streamlabs_wdt_driver);