Add hwmon driver for the ARCTIC Fan Controller, a USB HID device
(VID 0x3904, PID 0xF001) with 10 fan channels. Exposes fan speed in
RPM (read-only) and PWM duty cycle (0-255, read/write) via sysfs.
The device pushes IN reports at ~1 Hz containing RPM readings. PWM is
set via OUT reports; the device applies the new duty cycle and sends
back a 2-byte ACK (Report ID 0x02). The driver waits up to 1 s for
the ACK using a completion. Measured device latency: max ~563 ms over
500 iterations. PWM control is manual-only: the device never changes
duty cycle autonomously.
raw_event() may run in hardirq context, so fan_rpm[] is protected by
a spinlock with irq-save. pwm_duty[] is also protected by this spinlock
because reset_resume() clears it outside the hwmon core lock. The OUT
report buffer is built and write_pending is armed under the same lock so
that no reset_resume() can race with the pwm_duty[] snapshot. priv->buf
is exclusively accessed by write(), which the hwmon core serializes.
Signed-off-by: Aureo Serrano de Souza <aureo.serrano@arctic.de>
---
Thanks to Guenter Roeck and Thomas Weißschuh for the reviews.
Changes since v5:
- arctic_fan_probe(): switch from devm_hwmon_device_register_with_info()
to hwmon_device_register_with_info(); store the returned pointer in
priv->hwmon_dev for explicit teardown in remove()
- arctic_fan_remove(): call hwmon_device_unregister(priv->hwmon_dev)
before hid_device_io_stop/hid_hw_close/hid_hw_stop; this closes the
use-after-free window where a concurrent sysfs write could call
hid_hw_output_report() on an already-stopped device; matches the
removal pattern used by nzxt-smart2 and aquacomputer_d5next
- arctic_fan_write(): expand write_pending comment to document the
residual theoretical late-ACK race (unfixable without a correlation
ID in the device ACK report) and its practical impossibility (observed
max ACK latency ~563 ms, timeout 1 s; a delay > 1 s indicates a
non-functional device)
- arctic_fan_reset_resume(), arctic_fan_read(), arctic_fan_write():
extend in_report_lock coverage to pwm_duty[]; reset_resume() clears
pwm_duty[] outside the hwmon core lock, so all paths that read or
write pwm_duty[] now hold in_report_lock to prevent a data race
during resume
- arctic_fan_write(): build the OUT report buffer inside in_report_lock
so reset_resume() cannot clear pwm_duty[] between the pwm_duty[]
snapshot and the buffer write; this makes the lock coverage complete
Changes since v4:
- arctic_fan_write(): switch to wait_for_completion_timeout() (non-
interruptible); eliminates the signal-interrupted write case of the
late-ACK race that write_pending could not fully prevent
- arctic_fan_write(): guard pwm_duty[channel] commit with
ack_status == 0 check; a device error ACK (status 0x01) no longer
silently poisons the cached duty used in future OUT reports
- arctic_fan_probe()/remove(): replace devm_add_action_or_reset() +
no-op remove() with explicit hid_device_io_stop/hid_hw_close/
hid_hw_stop in remove(); devm_add_action_or_reset() was called after
hdev->driver = NULL, causing a NULL deref in hid_hw_close() on unbind
- add reset_resume callback: device resets PWM to hardware defaults on
power loss during suspend; driver now clears cached pwm_duty[] on
reset-resume so stale pre-suspend values are not re-sent as if valid
- Documentation/hwmon/arctic_fan_controller.rst: document suspend/
resume behaviour and the updated pwm[1-10] read semantics
Changes since v3:
- buf[]: upgrade from __aligned(8) to ____cacheline_aligned so the
DMA buffer occupies its own cache line, preventing false sharing with
adjacent fan_rpm[]/pwm_duty[] fields on non-coherent architectures
- arctic_fan_write(): add write_pending flag (protected by
in_report_lock) so raw_event() delivers ACKs only while a write is
in flight
- arctic_fan_write(): commit pwm_duty[channel] only after the device
ACKs the command; a failed or timed-out write no longer leaves a
stale value in the cached duty state
- arctic_fan_probe(): start IO (hid_device_io_start) before registering
with hwmon; previously a sysfs write arriving between hwmon
registration and io_start could send an OUT report whose ACK would be
discarded by the HID core, causing a spurious timeout
- Documentation/hwmon/arctic_fan_controller.rst: document that cached
PWM values start at 0 (hardware state unknown at probe) and that each
OUT report carries all 10 channel values
Changes since v2:
- buf[]: add __aligned(8) for DMA safety
- ARCTIC_ACK_TIMEOUT_MS: restore 1000 ms; note observed max ~563 ms
- arctic_fan_parse_report(): replace hwmon_lock/hwmon_unlock with
spin_lock_irqsave; hwmon_lock() may sleep and is unsafe when
raw_event() runs in hardirq/softirq context
- arctic_fan_raw_event(): use spin_lock_irqsave for ACK path
- arctic_fan_write(): use spin_lock_irqsave for completion reinit
- arctic_fan_write(): clamp val to [0, 255] before u8 cast
- remove priv->hwmon_dev (no longer needed)
Changes since v1:
- Use hid_dbg() instead of module_param debug flag
- Move hid_device_id table adjacent to hid_driver struct
- Use get_unaligned_le16() for RPM parsing
- Remove impossible bounds/NULL checks; remove retry loop
- Add hid_is_usb() guard
- Do not update pwm_duty from IN reports (device is manual-only)
- Add completion/ACK mechanism for OUT report acknowledgement
- Add Documentation/hwmon/arctic_fan_controller.rst and MAINTAINERS
diff --git a/Documentation/hwmon/arctic_fan_controller.rst b/Documentation/hwmon/arctic_fan_controller.rst
new file mode 100644
index 0000000000..b5be88ae46
--- /dev/null
+++ b/Documentation/hwmon/arctic_fan_controller.rst
@@ -0,0 +1,56 @@
+.. SPDX-License-Identifier: GPL-2.0-or-later
+
+Kernel driver arctic_fan_controller
+=====================================
+
+Supported devices:
+
+* ARCTIC Fan Controller (USB HID, VID 0x3904, PID 0xF001)
+
+Author: Aureo Serrano de Souza <aureo.serrano@arctic.de>
+
+Description
+-----------
+
+This driver provides hwmon support for the ARCTIC Fan Controller, a USB
+Custom HID device with 10 fan channels. The device sends IN reports about
+once per second containing current RPM values (bytes 11-30, 10 x uint16 LE).
+Fan speed control is manual-only: the device does not change PWM
+autonomously; it only applies a new duty cycle when it receives an OUT
+report from the host.
+
+After the device applies an OUT report, it sends back a 2-byte ACK IN
+report (Report ID 0x02, byte 1 = 0x00 on success) confirming the command
+was applied.
+
+Usage notes
+-----------
+
+Since it is a USB device, hotplug is supported. The device is autodetected.
+
+The device does not support GET_REPORT, so the driver cannot read back the
+current hardware PWM state at probe time. The cached PWM values (readable
+via pwm[1-10]) start at 0 and reflect only values that have been
+successfully written. Because each OUT report carries all 10 channel values,
+writing a single channel also sends the cached values for all other channels.
+Users should set all channels to the desired values before relying on the
+cached state.
+
+On system suspend, the device may lose power and reset its PWM channels to
+hardware defaults. The driver clears its cached duty values on resume so
+that reads reflect the unknown hardware state rather than stale pre-suspend
+values. Userspace is responsible for re-applying the desired duty cycles
+after resume.
+
+Sysfs entries
+-------------
+
+================ ==============================================================
+fan[1-10]_input Fan speed in RPM (read-only). Updated from IN reports at ~1 Hz.
+pwm[1-10] PWM duty cycle (0-255). Write: sends an OUT report setting the
+ duty cycle (scaled from 0-255 to 0-100% for the device);
+ the cached value is updated only after the device ACKs the
+ command with a success status. Read: returns the last
+ successfully written value; initialized to 0 at driver load
+ and after resume (hardware state unknown).
+================ ==============================================================
diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
index b2ca8513cf..c34713040e 100644
--- a/Documentation/hwmon/index.rst
+++ b/Documentation/hwmon/index.rst
@@ -42,6 +42,7 @@ Hardware Monitoring Kernel Drivers
aht10
amc6821
aquacomputer_d5next
+ arctic_fan_controller
asb100
asc7621
aspeed-g6-pwm-tach
diff --git a/MAINTAINERS b/MAINTAINERS
index 96ea84948d..ec3112bd41 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2053,6 +2053,13 @@ S: Maintained
F: drivers/net/arcnet/
F: include/uapi/linux/if_arcnet.h
+ARCTIC FAN CONTROLLER DRIVER
+M: Aureo Serrano de Souza <aureo.serrano@arctic.de>
+L: linux-hwmon@vger.kernel.org
+S: Maintained
+F: Documentation/hwmon/arctic_fan_controller.rst
+F: drivers/hwmon/arctic_fan_controller.c
+
ARM AND ARM64 SoC SUB-ARCHITECTURES (COMMON PARTS)
M: Arnd Bergmann <arnd@arndb.de>
M: Krzysztof Kozlowski <krzk@kernel.org>
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 328867242c..6c90a8dd40 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -388,6 +388,18 @@ config SENSORS_APPLESMC
Say Y here if you have an applicable laptop and want to experience
the awesome power of applesmc.
+config SENSORS_ARCTIC_FAN_CONTROLLER
+ tristate "ARCTIC Fan Controller"
+ depends on USB_HID
+ help
+ If you say yes here you get support for the ARCTIC Fan Controller,
+ a USB HID device (VID 0x3904, PID 0xF001) with 10 fan channels.
+ The driver exposes fan speed (RPM) and PWM control via the hwmon
+ sysfs interface.
+
+ This driver can also be built as a module. If so, the module
+ will be called arctic_fan_controller.
+
config SENSORS_ARM_SCMI
tristate "ARM SCMI Sensors"
depends on ARM_SCMI_PROTOCOL
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index 5833c807c6..ef831c3375 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -49,6 +49,7 @@ obj-$(CONFIG_SENSORS_ADT7475) += adt7475.o
obj-$(CONFIG_SENSORS_AHT10) += aht10.o
obj-$(CONFIG_SENSORS_APPLESMC) += applesmc.o
obj-$(CONFIG_SENSORS_AQUACOMPUTER_D5NEXT) += aquacomputer_d5next.o
+obj-$(CONFIG_SENSORS_ARCTIC_FAN_CONTROLLER) += arctic_fan_controller.o
obj-$(CONFIG_SENSORS_ARM_SCMI) += scmi-hwmon.o
obj-$(CONFIG_SENSORS_ARM_SCPI) += scpi-hwmon.o
obj-$(CONFIG_SENSORS_AS370) += as370-hwmon.o
diff --git a/drivers/hwmon/arctic_fan_controller.c b/drivers/hwmon/arctic_fan_controller.c
new file mode 100644
index 0000000000..2bfb003f01
--- /dev/null
+++ b/drivers/hwmon/arctic_fan_controller.c
@@ -0,0 +1,371 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Linux hwmon driver for ARCTIC Fan Controller
+ *
+ * USB Custom HID device with 10 fan channels.
+ * Exposes fan RPM (input) and PWM (0-255) via hwmon. Device pushes IN reports
+ * at ~1 Hz; no GET_REPORT. OUT reports set PWM duty (bytes 1-10, 0-100%).
+ * PWM is manual-only: the device does not change duty autonomously, only
+ * when it receives an OUT report from the host.
+ */
+
+#include <linux/cache.h>
+#include <linux/completion.h>
+#include <linux/err.h>
+#include <linux/hid.h>
+#include <linux/hwmon.h>
+#include <linux/jiffies.h>
+#include <linux/minmax.h>
+#include <linux/module.h>
+#include <linux/spinlock.h>
+#include <linux/string.h>
+#include <linux/unaligned.h>
+
+#define ARCTIC_VID 0x3904
+#define ARCTIC_PID 0xF001
+#define ARCTIC_NUM_FANS 10
+#define ARCTIC_OUTPUT_REPORT_ID 0x01
+#define ARCTIC_REPORT_LEN 32
+#define ARCTIC_RPM_OFFSET 11 /* bytes 11-30: 10 x uint16 LE */
+/* ACK report: device sends Report ID 0x02, 2 bytes (ID + status) after applying OUT report */
+#define ARCTIC_ACK_REPORT_ID 0x02
+#define ARCTIC_ACK_REPORT_LEN 2
+/*
+ * Time to wait for ACK report after send.
+ * Measured over 500 iterations: max ~563 ms. Keep 1 s as margin.
+ */
+#define ARCTIC_ACK_TIMEOUT_MS 1000
+
+struct arctic_fan_data {
+ struct hid_device *hdev;
+ struct device *hwmon_dev; /* stored for explicit unregister in remove() */
+ spinlock_t in_report_lock; /* protects fan_rpm, ack_status, write_pending, pwm_duty */
+ struct completion in_report_received; /* ACK (ID 0x02) received in raw_event */
+ int ack_status; /* 0 = OK, negative errno on device error */
+ bool write_pending; /* true while an OUT report ACK is in flight */
+ u32 fan_rpm[ARCTIC_NUM_FANS];
+ u8 pwm_duty[ARCTIC_NUM_FANS]; /* 0-255 matching sysfs range; converted to 0-100 on send */
+ /*
+ * OUT report buffer. Cache-line aligned so it occupies its own cache
+ * line, preventing DMA cache-coherency issues with adjacent fields
+ * (fan_rpm[], pwm_duty[]) on non-coherent architectures.
+ * Embedded in the devm_kzalloc'd struct so it is heap-allocated and
+ * passes usb_hcd_map_urb_for_dma(). Serialized by the hwmon core.
+ */
+ u8 buf[ARCTIC_REPORT_LEN] ____cacheline_aligned;
+};
+
+/*
+ * Parse RPM values from the periodic status report (10 x uint16 LE at rpm_off).
+ * pwm_duty is not updated from the report: the device is manual-only, so the
+ * host cache is the authoritative source for PWM.
+ * Called from raw_event which may run in IRQ context; must not sleep.
+ */
+static void arctic_fan_parse_report(struct arctic_fan_data *priv, u8 *buf,
+ int len, int rpm_off)
+{
+ unsigned long flags;
+ int i;
+
+ if (len < rpm_off + 20)
+ return;
+
+ spin_lock_irqsave(&priv->in_report_lock, flags);
+ for (i = 0; i < ARCTIC_NUM_FANS; i++)
+ priv->fan_rpm[i] = get_unaligned_le16(&buf[rpm_off + i * 2]);
+ spin_unlock_irqrestore(&priv->in_report_lock, flags);
+}
+
+/*
+ * raw_event: IN reports.
+ *
+ * Status report: Report ID 0x01, 32 bytes:
+ * byte 0 = report ID, bytes 1-10 = PWM 0-100%, bytes 11-30 = 10 x RPM uint16 LE.
+ * Device pushes these at ~1 Hz; no GET_REPORT.
+ *
+ * ACK report: Report ID 0x02, 2 bytes:
+ * byte 0 = 0x02, byte 1 = status (0x00 = OK, 0x01 = ERROR).
+ * Sent once after accepting and applying an OUT report (ID 0x01).
+ */
+static int arctic_fan_raw_event(struct hid_device *hdev,
+ struct hid_report *report, u8 *data, int size)
+{
+ struct arctic_fan_data *priv = hid_get_drvdata(hdev);
+ unsigned long flags;
+
+ hid_dbg(hdev, "arctic_fan: raw_event id=%u size=%d\n", report->id, size);
+
+ if (report->id == ARCTIC_ACK_REPORT_ID && size == ARCTIC_ACK_REPORT_LEN) {
+ spin_lock_irqsave(&priv->in_report_lock, flags);
+ /*
+ * Only deliver if a write is in flight. This prevents a
+ * late-arriving ACK from a timed-out write from erroneously
+ * satisfying a subsequent write's completion wait.
+ */
+ if (priv->write_pending) {
+ priv->ack_status = data[1] == 0x00 ? 0 : -EIO;
+ complete(&priv->in_report_received);
+ }
+ spin_unlock_irqrestore(&priv->in_report_lock, flags);
+ return 0;
+ }
+
+ if (report->id != ARCTIC_OUTPUT_REPORT_ID || size != ARCTIC_REPORT_LEN) {
+ hid_dbg(hdev, "arctic_fan: raw_event id=%u size=%d ignored\n",
+ report->id, size);
+ return 0;
+ }
+
+ arctic_fan_parse_report(priv, data, size, ARCTIC_RPM_OFFSET);
+ return 0;
+}
+
+static umode_t arctic_fan_is_visible(const void *data,
+ enum hwmon_sensor_types type,
+ u32 attr, int channel)
+{
+ if (type == hwmon_fan && attr == hwmon_fan_input)
+ return 0444;
+ if (type == hwmon_pwm && attr == hwmon_pwm_input)
+ return 0644;
+ return 0;
+}
+
+static int arctic_fan_read(struct device *dev, enum hwmon_sensor_types type,
+ u32 attr, int channel, long *val)
+{
+ struct arctic_fan_data *priv = dev_get_drvdata(dev);
+ unsigned long flags;
+
+ if (type == hwmon_fan && attr == hwmon_fan_input) {
+ spin_lock_irqsave(&priv->in_report_lock, flags);
+ *val = priv->fan_rpm[channel];
+ spin_unlock_irqrestore(&priv->in_report_lock, flags);
+ return 0;
+ }
+ if (type == hwmon_pwm && attr == hwmon_pwm_input) {
+ spin_lock_irqsave(&priv->in_report_lock, flags);
+ *val = priv->pwm_duty[channel];
+ spin_unlock_irqrestore(&priv->in_report_lock, flags);
+ return 0;
+ }
+ return -EINVAL;
+}
+
+static int arctic_fan_write(struct device *dev, enum hwmon_sensor_types type,
+ u32 attr, int channel, long val)
+{
+ struct arctic_fan_data *priv = dev_get_drvdata(dev);
+ u8 new_duty = (u8)clamp_val(val, 0, 255);
+ unsigned long flags;
+ unsigned long t;
+ int i, ret;
+
+ /*
+ * Build the buffer and arm write_pending under in_report_lock so that
+ * reset_resume() cannot clear pwm_duty[] between the pwm_duty[] read
+ * and the buffer write, and raw_event() cannot deliver a stale ACK
+ * from a previous write into this write's completion.
+ *
+ * priv->buf is heap-allocated (embedded in the devm_kzalloc'd struct),
+ * satisfying usb_hcd_map_urb_for_dma(). Exclusively accessed by
+ * write() which the hwmon core serializes.
+ *
+ * pwm_duty[channel] is committed only after a positive device ACK so a
+ * failed or timed-out write does not corrupt the cached state.
+ *
+ * Residual theoretical race: if write A times out (write_pending
+ * cleared), write B sets write_pending = true, and a late ACK from
+ * write A—delayed beyond ARCTIC_ACK_TIMEOUT_MS—arrives during write
+ * B's pending window, it would falsely satisfy write B's completion.
+ * This cannot be prevented in driver code without protocol support
+ * (for example, a correlation ID echoed in the device ACK report).
+ * In testing, observed ACK latency stayed below the 1 s timeout
+ * (maximum ~563 ms over 500 iterations).
+ *
+ * The wait is non-interruptible so that a signal cannot cause write()
+ * to return early while the OUT report is already in flight; an
+ * interruptible early return would create the same late-ACK window
+ * without even the timeout guard.
+ * Serialized by the hwmon core: only one arctic_fan_write() at a time.
+ * Use irqsave to match the IRQ context in which raw_event may run.
+ */
+ spin_lock_irqsave(&priv->in_report_lock, flags);
+ priv->buf[0] = ARCTIC_OUTPUT_REPORT_ID;
+ for (i = 0; i < ARCTIC_NUM_FANS; i++) {
+ u8 d = i == channel ? new_duty : priv->pwm_duty[i];
+
+ priv->buf[1 + i] = DIV_ROUND_CLOSEST((unsigned int)d * 100, 255);
+ }
+ priv->ack_status = -ETIMEDOUT;
+ priv->write_pending = true;
+ reinit_completion(&priv->in_report_received);
+ spin_unlock_irqrestore(&priv->in_report_lock, flags);
+
+ ret = hid_hw_output_report(priv->hdev, priv->buf, ARCTIC_REPORT_LEN);
+ if (ret < 0) {
+ spin_lock_irqsave(&priv->in_report_lock, flags);
+ priv->write_pending = false;
+ spin_unlock_irqrestore(&priv->in_report_lock, flags);
+ return ret;
+ }
+
+ t = wait_for_completion_timeout(&priv->in_report_received,
+ msecs_to_jiffies(ARCTIC_ACK_TIMEOUT_MS));
+ spin_lock_irqsave(&priv->in_report_lock, flags);
+ priv->write_pending = false;
+ /* Commit inside the lock so reset_resume() cannot race with this write */
+ if (t && priv->ack_status == 0)
+ priv->pwm_duty[channel] = new_duty;
+ spin_unlock_irqrestore(&priv->in_report_lock, flags);
+
+ if (!t)
+ return -ETIMEDOUT;
+ return priv->ack_status; /* 0=OK, -EIO=device error */
+}
+
+static const struct hwmon_ops arctic_fan_ops = {
+ .is_visible = arctic_fan_is_visible,
+ .read = arctic_fan_read,
+ .write = arctic_fan_write,
+};
+
+static const struct hwmon_channel_info *arctic_fan_info[] = {
+ HWMON_CHANNEL_INFO(fan,
+ HWMON_F_INPUT, HWMON_F_INPUT, HWMON_F_INPUT,
+ HWMON_F_INPUT, HWMON_F_INPUT, HWMON_F_INPUT,
+ HWMON_F_INPUT, HWMON_F_INPUT, HWMON_F_INPUT,
+ HWMON_F_INPUT),
+ HWMON_CHANNEL_INFO(pwm,
+ HWMON_PWM_INPUT, HWMON_PWM_INPUT, HWMON_PWM_INPUT,
+ HWMON_PWM_INPUT, HWMON_PWM_INPUT, HWMON_PWM_INPUT,
+ HWMON_PWM_INPUT, HWMON_PWM_INPUT, HWMON_PWM_INPUT,
+ HWMON_PWM_INPUT),
+ NULL
+};
+
+static const struct hwmon_chip_info arctic_fan_chip_info = {
+ .ops = &arctic_fan_ops,
+ .info = arctic_fan_info,
+};
+
+static int arctic_fan_reset_resume(struct hid_device *hdev)
+{
+ struct arctic_fan_data *priv = hid_get_drvdata(hdev);
+ unsigned long flags;
+
+ /*
+ * The device resets its PWM channels to hardware defaults on power
+ * loss during suspend. Clear the cached duty values so they reflect
+ * the unknown hardware state, consistent with probe-time behaviour
+ * (the device has no GET_REPORT support). Hold in_report_lock so
+ * this does not race with a concurrent pwm read or write callback.
+ */
+ spin_lock_irqsave(&priv->in_report_lock, flags);
+ memset(priv->pwm_duty, 0, sizeof(priv->pwm_duty));
+ spin_unlock_irqrestore(&priv->in_report_lock, flags);
+ return 0;
+}
+
+static int arctic_fan_probe(struct hid_device *hdev,
+ const struct hid_device_id *id)
+{
+ struct arctic_fan_data *priv;
+ int ret;
+
+ if (!hid_is_usb(hdev))
+ return -ENODEV;
+
+ ret = hid_parse(hdev);
+ if (ret)
+ return ret;
+
+ priv = devm_kzalloc(&hdev->dev, sizeof(*priv), GFP_KERNEL);
+ if (!priv)
+ return -ENOMEM;
+
+ priv->hdev = hdev;
+ spin_lock_init(&priv->in_report_lock);
+ init_completion(&priv->in_report_received);
+ hid_set_drvdata(hdev, priv);
+
+ ret = hid_hw_start(hdev, HID_CONNECT_DRIVER);
+ if (ret)
+ return ret;
+
+ ret = hid_hw_open(hdev);
+ if (ret)
+ goto out_stop;
+
+ /*
+ * Start IO before registering with hwmon. If IO were started after
+ * hwmon registration, a sysfs write arriving in that narrow window
+ * would send an OUT report but the ACK could not be delivered (the HID
+ * core discards events until io_started), causing a spurious timeout.
+ */
+ hid_device_io_start(hdev);
+
+ /*
+ * Use the non-devm variant and store the pointer so remove() can
+ * call hwmon_device_unregister() before tearing down the HID
+ * transport. devm_hwmon_device_register_with_info() would defer
+ * unregistration until after remove() returns, leaving a window
+ * where a concurrent sysfs write could call hid_hw_output_report()
+ * on an already-stopped device (use-after-free).
+ */
+ priv->hwmon_dev = hwmon_device_register_with_info(&hdev->dev, "arctic_fan",
+ priv, &arctic_fan_chip_info,
+ NULL);
+ if (IS_ERR(priv->hwmon_dev)) {
+ ret = PTR_ERR(priv->hwmon_dev);
+ goto out_close;
+ }
+
+ return 0;
+
+out_close:
+ hid_device_io_stop(hdev);
+ hid_hw_close(hdev);
+out_stop:
+ hid_hw_stop(hdev);
+ return ret;
+}
+
+static void arctic_fan_remove(struct hid_device *hdev)
+{
+ struct arctic_fan_data *priv = hid_get_drvdata(hdev);
+
+ /*
+ * Unregister hwmon before stopping the HID transport. This removes
+ * the sysfs files and waits for any in-progress write() callback to
+ * return, so no hwmon op can call hid_hw_output_report() after
+ * hid_hw_stop() frees the underlying USB resources.
+ * Matches the pattern used by nzxt-smart2 and aquacomputer_d5next.
+ */
+ hwmon_device_unregister(priv->hwmon_dev);
+ hid_device_io_stop(hdev);
+ hid_hw_close(hdev);
+ hid_hw_stop(hdev);
+}
+
+static const struct hid_device_id arctic_fan_id_table[] = {
+ { HID_USB_DEVICE(ARCTIC_VID, ARCTIC_PID) },
+ { }
+};
+MODULE_DEVICE_TABLE(hid, arctic_fan_id_table);
+
+static struct hid_driver arctic_fan_driver = {
+ .name = "arctic_fan",
+ .id_table = arctic_fan_id_table,
+ .probe = arctic_fan_probe,
+ .remove = arctic_fan_remove,
+ .raw_event = arctic_fan_raw_event,
+ .reset_resume = arctic_fan_reset_resume,
+};
+
+module_hid_driver(arctic_fan_driver);
+
+MODULE_AUTHOR("Aureo Serrano de Souza <aureo.serrano@arctic.de>");
+MODULE_DESCRIPTION("HID hwmon driver for ARCTIC Fan Controller");
+MODULE_LICENSE("GPL");
Hi, On Wed, Apr 01, 2026 at 07:25:54PM +0800, Aureo Serrano de Souza wrote: > Add hwmon driver for the ARCTIC Fan Controller, a USB HID device > (VID 0x3904, PID 0xF001) with 10 fan channels. Exposes fan speed in > RPM (read-only) and PWM duty cycle (0-255, read/write) via sysfs. > > The device pushes IN reports at ~1 Hz containing RPM readings. PWM is > set via OUT reports; the device applies the new duty cycle and sends > back a 2-byte ACK (Report ID 0x02). The driver waits up to 1 s for > the ACK using a completion. Measured device latency: max ~563 ms over > 500 iterations. PWM control is manual-only: the device never changes > duty cycle autonomously. > > raw_event() may run in hardirq context, so fan_rpm[] is protected by > a spinlock with irq-save. pwm_duty[] is also protected by this spinlock > because reset_resume() clears it outside the hwmon core lock. The OUT > report buffer is built and write_pending is armed under the same lock so > that no reset_resume() can race with the pwm_duty[] snapshot. priv->buf > is exclusively accessed by write(), which the hwmon core serializes. > > Signed-off-by: Aureo Serrano de Souza <aureo.serrano@arctic.de> > --- Looks like the patch is corrupted. Applying: hwmon: add driver for ARCTIC Fan Controller error: corrupt patch at line 587 error: could not build fake ancestor Patch failed at 0001 hwmon: add driver for ARCTIC Fan Controller I can not figure out what is wrong, but both git and patch report that it is corrupted. Please fix and resend. Thanks, Guenter
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