Documentation/hwmon/arctic_fan_controller.rst | 40 +++ Documentation/hwmon/index.rst | 1 + MAINTAINERS | 7 + drivers/hwmon/Kconfig | 12 + drivers/hwmon/Makefile | 1 + drivers/hwmon/arctic_fan_controller.c | 278 ++++++++++++++++++ 6 files changed, 339 insertions(+) create mode 100644 Documentation/hwmon/arctic_fan_controller.rst create mode 100644 drivers/hwmon/arctic_fan_controller.c
Add hwmon driver for the ARCTIC Fan Controller (USB HID VID 0x3904,
PID 0xF001) with 10 fan channels. Exposes fan RPM and PWM via sysfs.
Device pushes IN reports at ~1 Hz; PWM is set via interrupt OUT reports.
Fan speed control is manual-only: the device does not change PWM
autonomously. After applying an OUT report, the device sends back a
2-byte ACK (Report ID 0x02); the driver waits up to 1 s for this ACK
using a completion.
The report buffer is kmalloc'd per write for two reasons:
1. Stack placement (suggested by reviewers with __aligned()) was tested
but hard-rejected by usb_hcd_map_urb_for_dma(), which calls
object_is_on_stack() and returns -EAGAIN regardless of alignment
attributes. Confirmed on AMD X670E with AMD-Vi (IOMMU) enabled.
2. Struct-embedded placement (suggested as an alternative) would create
a shared resource between concurrent arctic_fan_write() calls, causing
a race if two users write different PWM channels simultaneously.
kmalloc per write avoids both problems: the buffer is heap-allocated
(passes DMA checks) and private to each write call (no sharing).
Signed-off-by: Aureo Serrano de Souza <aureo.serrano@arctic.de>
---
Hi,
Thanks for the detailed review. Here is v2 addressing your feedback.
If I missed anything, please let me know.
Changes since v1:
- Remove module_param debug flag; use hid_dbg() / dyndbg instead
- Move hid_device_id table next to hid_driver struct
- Replace spinlock_irqsave with mutex for fan_rpm/pwm_duty; use a
lightweight spinlock only to protect the completion signal shared with
raw_event() which runs in BH/softirq context
- Use guard() from cleanup.h to eliminate manual unlock on error paths
- Use get_unaligned_le16() for RPM parsing instead of manual byte shift
- Remove all impossible bounds/NULL checks that the hwmon core never triggers
- Remove retry loop; use a single hid_hw_output_report() call
- Add hid_is_usb() guard in probe
- Remove hwmon_dev field from struct; use local variable only
- Remove VID/PID from MODULE_DESCRIPTION
- Fix: do not update pwm_duty from IN reports; device is manual-only so
the host cache is the authoritative PWM source. This eliminates the race
where an incoming report could overwrite a value just written.
- Add completion/ACK mechanism: wait for device ACK after OUT report,
signalled from raw_event() via complete(); return device ACK status
- Report buffer is kmalloc'd per write; see commit message for full
rationale. In summary: stack placement (suggested with __aligned()) is
hard-rejected by usb_hcd_map_urb_for_dma() via object_is_on_stack();
struct-embedded placement (suggested as alternative) creates a shared
resource race between concurrent writes. kmalloc per write avoids both.
- Add Documentation/hwmon/arctic_fan_controller.rst to index.rst
- Add MAINTAINERS entry
Documentation/hwmon/arctic_fan_controller.rst | 40 +++
Documentation/hwmon/index.rst | 1 +
MAINTAINERS | 7 +
drivers/hwmon/Kconfig | 12 +
drivers/hwmon/Makefile | 1 +
drivers/hwmon/arctic_fan_controller.c | 278 ++++++++++++++++++
6 files changed, 339 insertions(+)
create mode 100644 Documentation/hwmon/arctic_fan_controller.rst
create mode 100644 drivers/hwmon/arctic_fan_controller.c
diff --git a/Documentation/hwmon/arctic_fan_controller.rst b/Documentation/hwmon/arctic_fan_controller.rst
new file mode 100644
index 000000000..58366551c
--- /dev/null
+++ b/Documentation/hwmon/arctic_fan_controller.rst
@@ -0,0 +1,40 @@
+.. 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.
+
+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). Read:
+ returns the last value written; the device is manual-only so
+ the host cache is authoritative.
+================ ==============================================================
diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
index b2ca8513c..c34713040 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 837db4f7b..8c32dddd6 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 486152a8e..b6ab72752 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 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 5833c807c..ef831c337 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 000000000..24db8a7ee
--- /dev/null
+++ b/drivers/hwmon/arctic_fan_controller.c
@@ -0,0 +1,278 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Linux hwmon driver for ARCTIC Fan Controller
+ *
+ * USB Custom HID device (VID 0x3904, PID 0xF001) 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/cleanup.h>
+#include <linux/completion.h>
+#include <linux/err.h>
+#include <linux/hid.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/jiffies.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/unaligned.h>
+
+#define ARCTIC_VID 0x3904
+#define ARCTIC_PID 0xF001
+#define ARCTIC_NUM_FANS 10
+#define ARCTIC_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 */
+#define ARCTIC_ACK_TIMEOUT_MS 1000
+
+struct arctic_fan_data {
+ struct hid_device *hdev;
+ struct mutex lock; /* protects fan_rpm, pwm_duty */
+ spinlock_t in_report_lock; /* protects ack_status and in_report_received */
+ struct completion in_report_received; /* ACK (ID 0x02) received in raw_event */
+ int ack_status; /* 0 = OK, negative errno on device error */
+ u32 fan_rpm[ARCTIC_NUM_FANS];
+ u8 pwm_duty[ARCTIC_NUM_FANS]; /* 0-255 matching sysfs range; converted to 0-100 on send */
+};
+
+/*
+ * 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.
+ */
+static void arctic_fan_parse_report(struct arctic_fan_data *priv, u8 *buf,
+ int len, int rpm_off)
+{
+ int i;
+
+ if (len < rpm_off + 20)
+ return;
+ {
+ guard(mutex)(&priv->lock);
+ for (i = 0; i < ARCTIC_NUM_FANS; i++)
+ priv->fan_rpm[i] = get_unaligned_le16(&buf[rpm_off + i * 2]);
+ }
+}
+
+/*
+ * 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);
+
+ 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(&priv->in_report_lock);
+ priv->ack_status = data[1] == 0x00 ? 0 : -EIO;
+ complete(&priv->in_report_received);
+ spin_unlock(&priv->in_report_lock);
+ return 0;
+ }
+
+ if (report->id != ARCTIC_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);
+
+ {
+ guard(mutex)(&priv->lock);
+ if (type == hwmon_fan && attr == hwmon_fan_input) {
+ *val = priv->fan_rpm[channel];
+ return 0;
+ }
+ if (type == hwmon_pwm && attr == hwmon_pwm_input) {
+ *val = priv->pwm_duty[channel];
+ 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 *buf;
+ long t;
+ int i, ret;
+
+ /*
+ * Must use a heap-allocated buffer: usb_hcd_map_urb_for_dma() rejects
+ * stack buffers with -EAGAIN, preventing USB transfers on DMA-capable
+ * host controllers.
+ */
+ buf = kmalloc(ARCTIC_REPORT_LEN, GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;
+
+ {
+ guard(mutex)(&priv->lock);
+ priv->pwm_duty[channel] = (u8)val;
+ buf[0] = ARCTIC_REPORT_ID;
+ for (i = 0; i < ARCTIC_NUM_FANS; i++)
+ buf[1 + i] = DIV_ROUND_CLOSEST((unsigned int)priv->pwm_duty[i] * 100, 255);
+ }
+ memset(buf + 11, 0, ARCTIC_REPORT_LEN - 11);
+
+ spin_lock_bh(&priv->in_report_lock);
+ priv->ack_status = -ETIMEDOUT;
+ reinit_completion(&priv->in_report_received);
+ spin_unlock_bh(&priv->in_report_lock);
+
+ ret = hid_hw_output_report(priv->hdev, buf, ARCTIC_REPORT_LEN);
+ kfree(buf);
+ if (ret < 0)
+ return ret;
+
+ t = wait_for_completion_interruptible_timeout(&priv->in_report_received,
+ msecs_to_jiffies(ARCTIC_ACK_TIMEOUT_MS));
+ if (t == 0)
+ return -ETIMEDOUT;
+ if (t < 0)
+ return t; /* interrupted by signal */
+ 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_probe(struct hid_device *hdev,
+ const struct hid_device_id *id)
+{
+ struct arctic_fan_data *priv;
+ struct device *hwmon_dev;
+ 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;
+ mutex_init(&priv->lock);
+ 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;
+
+ hid_device_io_start(hdev);
+
+ hwmon_dev = devm_hwmon_device_register_with_info(&hdev->dev, "arctic_fan",
+ priv, &arctic_fan_chip_info,
+ NULL);
+ if (IS_ERR(hwmon_dev)) {
+ ret = PTR_ERR(hwmon_dev);
+ goto out_close;
+ }
+ return 0;
+
+out_close:
+ hid_hw_close(hdev);
+out_stop:
+ hid_hw_stop(hdev);
+ return ret;
+}
+
+static void arctic_fan_remove(struct hid_device *hdev)
+{
+ 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,
+};
+
+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");
--
2.43.0Hi, On Fri, Mar 13, 2026 at 07:19:55PM +0800, Aureo Serrano de Souza wrote: > Add hwmon driver for the ARCTIC Fan Controller (USB HID VID 0x3904, > PID 0xF001) with 10 fan channels. Exposes fan RPM and PWM via sysfs. > Device pushes IN reports at ~1 Hz; PWM is set via interrupt OUT reports. > > Fan speed control is manual-only: the device does not change PWM > autonomously. After applying an OUT report, the device sends back a > 2-byte ACK (Report ID 0x02); the driver waits up to 1 s for this ACK > using a completion. > > The report buffer is kmalloc'd per write for two reasons: > > 1. Stack placement (suggested by reviewers with __aligned()) was tested > but hard-rejected by usb_hcd_map_urb_for_dma(), which calls > object_is_on_stack() and returns -EAGAIN regardless of alignment > attributes. Confirmed on AMD X670E with AMD-Vi (IOMMU) enabled. > > 2. Struct-embedded placement (suggested as an alternative) would create > a shared resource between concurrent arctic_fan_write() calls, causing > a race if two users write different PWM channels simultaneously. > > kmalloc per write avoids both problems: the buffer is heap-allocated > (passes DMA checks) and private to each write call (no sharing). > > Signed-off-by: Aureo Serrano de Souza <aureo.serrano@arctic.de> > --- Please also see AI review feedback at https://sashiko.dev/#/patchset/20260313111955.36811-1-aureo.serrano%40arctic.de. Thanks, Guenter
When sending new revisions, please don't send them as response to the
previous one. It results in much too large threads.
On 2026-03-13 19:19:55+0800, Aureo Serrano de Souza wrote:
> Add hwmon driver for the ARCTIC Fan Controller (USB HID VID 0x3904,
> PID 0xF001) with 10 fan channels. Exposes fan RPM and PWM via sysfs.
> Device pushes IN reports at ~1 Hz; PWM is set via interrupt OUT reports.
>
> Fan speed control is manual-only: the device does not change PWM
> autonomously. After applying an OUT report, the device sends back a
> 2-byte ACK (Report ID 0x02); the driver waits up to 1 s for this ACK
> using a completion.
>
> The report buffer is kmalloc'd per write for two reasons:
>
> 1. Stack placement (suggested by reviewers with __aligned()) was tested
> but hard-rejected by usb_hcd_map_urb_for_dma(), which calls
> object_is_on_stack() and returns -EAGAIN regardless of alignment
> attributes. Confirmed on AMD X670E with AMD-Vi (IOMMU) enabled.
Thanks for the clarifications!
> 2. Struct-embedded placement (suggested as an alternative) would create
> a shared resource between concurrent arctic_fan_write() calls, causing
> a race if two users write different PWM channels simultaneously.
>
> kmalloc per write avoids both problems: the buffer is heap-allocated
> (passes DMA checks) and private to each write call (no sharing).
>
> Signed-off-by: Aureo Serrano de Souza <aureo.serrano@arctic.de>
> ---
> Hi,
>
> Thanks for the detailed review. Here is v2 addressing your feedback.
> If I missed anything, please let me know.
(...)
> Documentation/hwmon/arctic_fan_controller.rst | 40 +++
> Documentation/hwmon/index.rst | 1 +
> MAINTAINERS | 7 +
> drivers/hwmon/Kconfig | 12 +
> drivers/hwmon/Makefile | 1 +
> drivers/hwmon/arctic_fan_controller.c | 278 ++++++++++++++++++
> 6 files changed, 339 insertions(+)
> create mode 100644 Documentation/hwmon/arctic_fan_controller.rst
> create mode 100644 drivers/hwmon/arctic_fan_controller.c
(...)
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index 486152a8e..b6ab72752 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 HID
Given the the driver will only ever probe for usb devices,
this could also '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/arctic_fan_controller.c b/drivers/hwmon/arctic_fan_controller.c
> new file mode 100644
> index 000000000..24db8a7ee
> --- /dev/null
> +++ b/drivers/hwmon/arctic_fan_controller.c
> @@ -0,0 +1,278 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Linux hwmon driver for ARCTIC Fan Controller
> + *
> + * USB Custom HID device (VID 0x3904, PID 0xF001) with 10 fan channels.
I would also drop the VID and PID from here. It has no additional value.
> + * 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/cleanup.h>
> +#include <linux/completion.h>
> +#include <linux/err.h>
> +#include <linux/hid.h>
> +#include <linux/hwmon.h>
> +#include <linux/hwmon-sysfs.h>
> +#include <linux/jiffies.h>
> +#include <linux/kernel.h>
Try to avoid kernel.h. It includes everything and the kitchensink.
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/slab.h>
> +#include <linux/spinlock.h>
> +#include <linux/unaligned.h>
> +
> +#define ARCTIC_VID 0x3904
> +#define ARCTIC_PID 0xF001
> +#define ARCTIC_NUM_FANS 10
> +#define ARCTIC_REPORT_ID 0x01
> +#define ARCTIC_REPORT_LEN 32
As there is also ARCTIC_*ACK*_REPORT_ID, maybe call this one
ARCTIC_*OUTPUT*_REPORT_ID, etc.
> +#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 */
> +#define ARCTIC_ACK_TIMEOUT_MS 1000
One second is a very long time. How long does the device take in
practice?
> +struct arctic_fan_data {
> + struct hid_device *hdev;
> + struct mutex lock; /* protects fan_rpm, pwm_duty */
> + spinlock_t in_report_lock; /* protects ack_status and in_report_received */
> + struct completion in_report_received; /* ACK (ID 0x02) received in raw_event */
> + int ack_status; /* 0 = OK, negative errno on device error */
> + u32 fan_rpm[ARCTIC_NUM_FANS];
> + u8 pwm_duty[ARCTIC_NUM_FANS]; /* 0-255 matching sysfs range; converted to 0-100 on send */
> +};
> +
> +/*
> + * 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.
> + */
> +static void arctic_fan_parse_report(struct arctic_fan_data *priv, u8 *buf,
> + int len, int rpm_off)
> +{
> + int i;
> +
> + if (len < rpm_off + 20)
> + return;
> + {
Avoid scopes like this. Here it is not needed at all and in those cases
where you need a new scope for guard() use scoped_guard().
> + guard(mutex)(&priv->lock);
> + for (i = 0; i < ARCTIC_NUM_FANS; i++)
Nowadays you could declare 'int i' inside the for(). Your choice.
> + priv->fan_rpm[i] = get_unaligned_le16(&buf[rpm_off + i * 2]);
> + }
> +}
(...)
> +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 *buf;
> + long t;
> + int i, ret;
> +
> + /*
> + * Must use a heap-allocated buffer: usb_hcd_map_urb_for_dma() rejects
> + * stack buffers with -EAGAIN, preventing USB transfers on DMA-capable
> + * host controllers.
> + */
> + buf = kmalloc(ARCTIC_REPORT_LEN, GFP_KERNEL);
> + if (!buf)
> + return -ENOMEM;
> +
> + {
> + guard(mutex)(&priv->lock);
> + priv->pwm_duty[channel] = (u8)val;
> + buf[0] = ARCTIC_REPORT_ID;
> + for (i = 0; i < ARCTIC_NUM_FANS; i++)
> + buf[1 + i] = DIV_ROUND_CLOSEST((unsigned int)priv->pwm_duty[i] * 100, 255);
> + }
> + memset(buf + 11, 0, ARCTIC_REPORT_LEN - 11);
The magic '11' should be '1 + ARCTIC_NUM_FANS'.
Or even easier, use kzalloc() above.
> +
> + spin_lock_bh(&priv->in_report_lock);
> + priv->ack_status = -ETIMEDOUT;
> + reinit_completion(&priv->in_report_received);
> + spin_unlock_bh(&priv->in_report_lock);
> +
> + ret = hid_hw_output_report(priv->hdev, buf, ARCTIC_REPORT_LEN);
> + kfree(buf);
> + if (ret < 0)
> + return ret;
> +
> + t = wait_for_completion_interruptible_timeout(&priv->in_report_received,
Without the implicit locking from the hwmon core, this would be racy
against concurrent invocations of arctic_fan_write().
Could you add a comment for that?
> + msecs_to_jiffies(ARCTIC_ACK_TIMEOUT_MS));
> + if (t == 0)
> + return -ETIMEDOUT;
> + if (t < 0)
> + return t; /* interrupted by signal */
First test for errors (t < 0), then non-error cases 't == 0'.
> + return priv->ack_status; /* 0=OK, -EIO=device error */
> +}
(...)
> +static int arctic_fan_probe(struct hid_device *hdev,
> + const struct hid_device_id *id)
> +{
> + struct arctic_fan_data *priv;
> + struct device *hwmon_dev;
> + 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;
> + mutex_init(&priv->lock);
Use devm_mutex_init().
> + spin_lock_init(&priv->in_report_lock);
> + init_completion(&priv->in_report_received);
> + hid_set_drvdata(hdev, priv);
(...)
On Fri, Mar 13, 2026 at 07:19:55PM +0800, Aureo Serrano de Souza wrote:
> Add hwmon driver for the ARCTIC Fan Controller (USB HID VID 0x3904,
> PID 0xF001) with 10 fan channels. Exposes fan RPM and PWM via sysfs.
> Device pushes IN reports at ~1 Hz; PWM is set via interrupt OUT reports.
>
> Fan speed control is manual-only: the device does not change PWM
> autonomously. After applying an OUT report, the device sends back a
> 2-byte ACK (Report ID 0x02); the driver waits up to 1 s for this ACK
> using a completion.
>
> The report buffer is kmalloc'd per write for two reasons:
>
> 1. Stack placement (suggested by reviewers with __aligned()) was tested
> but hard-rejected by usb_hcd_map_urb_for_dma(), which calls
> object_is_on_stack() and returns -EAGAIN regardless of alignment
> attributes. Confirmed on AMD X670E with AMD-Vi (IOMMU) enabled.
>
> 2. Struct-embedded placement (suggested as an alternative) would create
> a shared resource between concurrent arctic_fan_write() calls, causing
> a race if two users write different PWM channels simultaneously.
>
> kmalloc per write avoids both problems: the buffer is heap-allocated
> (passes DMA checks) and private to each write call (no sharing).
The second problem does not exist since the hwmon core serializes sysfs
attribute accesses, and a single once-allocated buffer would be sufficient
for the same reason.
>
> Signed-off-by: Aureo Serrano de Souza <aureo.serrano@arctic.de>
> ---
> Hi,
>
> Thanks for the detailed review. Here is v2 addressing your feedback.
> If I missed anything, please let me know.
>
> Changes since v1:
> - Remove module_param debug flag; use hid_dbg() / dyndbg instead
> - Move hid_device_id table next to hid_driver struct
> - Replace spinlock_irqsave with mutex for fan_rpm/pwm_duty; use a
> lightweight spinlock only to protect the completion signal shared with
> raw_event() which runs in BH/softirq context
> - Use guard() from cleanup.h to eliminate manual unlock on error paths
> - Use get_unaligned_le16() for RPM parsing instead of manual byte shift
> - Remove all impossible bounds/NULL checks that the hwmon core never triggers
> - Remove retry loop; use a single hid_hw_output_report() call
> - Add hid_is_usb() guard in probe
> - Remove hwmon_dev field from struct; use local variable only
> - Remove VID/PID from MODULE_DESCRIPTION
> - Fix: do not update pwm_duty from IN reports; device is manual-only so
> the host cache is the authoritative PWM source. This eliminates the race
> where an incoming report could overwrite a value just written.
> - Add completion/ACK mechanism: wait for device ACK after OUT report,
> signalled from raw_event() via complete(); return device ACK status
> - Report buffer is kmalloc'd per write; see commit message for full
> rationale. In summary: stack placement (suggested with __aligned()) is
> hard-rejected by usb_hcd_map_urb_for_dma() via object_is_on_stack();
> struct-embedded placement (suggested as alternative) creates a shared
> resource race between concurrent writes. kmalloc per write avoids both.
> - Add Documentation/hwmon/arctic_fan_controller.rst to index.rst
> - Add MAINTAINERS entry
>
> Documentation/hwmon/arctic_fan_controller.rst | 40 +++
> Documentation/hwmon/index.rst | 1 +
> MAINTAINERS | 7 +
> drivers/hwmon/Kconfig | 12 +
> drivers/hwmon/Makefile | 1 +
> drivers/hwmon/arctic_fan_controller.c | 278 ++++++++++++++++++
> 6 files changed, 339 insertions(+)
> create mode 100644 Documentation/hwmon/arctic_fan_controller.rst
> create mode 100644 drivers/hwmon/arctic_fan_controller.c
>
> diff --git a/Documentation/hwmon/arctic_fan_controller.rst b/Documentation/hwmon/arctic_fan_controller.rst
> new file mode 100644
> index 000000000..58366551c
> --- /dev/null
> +++ b/Documentation/hwmon/arctic_fan_controller.rst
> @@ -0,0 +1,40 @@
> +.. 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.
> +
> +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). Read:
> + returns the last value written; the device is manual-only so
> + the host cache is authoritative.
> +================ ==============================================================
> diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
> index b2ca8513c..c34713040 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 837db4f7b..8c32dddd6 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 486152a8e..b6ab72752 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 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 5833c807c..ef831c337 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 000000000..24db8a7ee
> --- /dev/null
> +++ b/drivers/hwmon/arctic_fan_controller.c
> @@ -0,0 +1,278 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Linux hwmon driver for ARCTIC Fan Controller
> + *
> + * USB Custom HID device (VID 0x3904, PID 0xF001) 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/cleanup.h>
> +#include <linux/completion.h>
> +#include <linux/err.h>
> +#include <linux/hid.h>
> +#include <linux/hwmon.h>
> +#include <linux/hwmon-sysfs.h>
Not needed.
> +#include <linux/jiffies.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/slab.h>
> +#include <linux/spinlock.h>
> +#include <linux/unaligned.h>
> +
> +#define ARCTIC_VID 0x3904
> +#define ARCTIC_PID 0xF001
> +#define ARCTIC_NUM_FANS 10
> +#define ARCTIC_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 */
> +#define ARCTIC_ACK_TIMEOUT_MS 1000
> +
> +struct arctic_fan_data {
> + struct hid_device *hdev;
> + struct mutex lock; /* protects fan_rpm, pwm_duty */
> + spinlock_t in_report_lock; /* protects ack_status and in_report_received */
> + struct completion in_report_received; /* ACK (ID 0x02) received in raw_event */
> + int ack_status; /* 0 = OK, negative errno on device error */
> + u32 fan_rpm[ARCTIC_NUM_FANS];
> + u8 pwm_duty[ARCTIC_NUM_FANS]; /* 0-255 matching sysfs range; converted to 0-100 on send */
> +};
> +
> +/*
> + * 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.
> + */
> +static void arctic_fan_parse_report(struct arctic_fan_data *priv, u8 *buf,
> + int len, int rpm_off)
> +{
> + int i;
> +
> + if (len < rpm_off + 20)
> + return;
> + {
> + guard(mutex)(&priv->lock);
The { } around the guard() are unnecessary, both here and elsewhere in the code.
If the guard() is added is because the call is from an event handler,
use hwmon_lock() and hwmon_unlock() to serialize accesses.
> + for (i = 0; i < ARCTIC_NUM_FANS; i++)
> + priv->fan_rpm[i] = get_unaligned_le16(&buf[rpm_off + i * 2]);
> + }
> +}
> +
> +/*
> + * 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);
> +
> + 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(&priv->in_report_lock);
> + priv->ack_status = data[1] == 0x00 ? 0 : -EIO;
> + complete(&priv->in_report_received);
> + spin_unlock(&priv->in_report_lock);
> + return 0;
> + }
> +
> + if (report->id != ARCTIC_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);
> +
> + {
> + guard(mutex)(&priv->lock);
> + if (type == hwmon_fan && attr == hwmon_fan_input) {
> + *val = priv->fan_rpm[channel];
> + return 0;
> + }
> + if (type == hwmon_pwm && attr == hwmon_pwm_input) {
> + *val = priv->pwm_duty[channel];
> + 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 *buf;
> + long t;
> + int i, ret;
> +
> + /*
> + * Must use a heap-allocated buffer: usb_hcd_map_urb_for_dma() rejects
> + * stack buffers with -EAGAIN, preventing USB transfers on DMA-capable
> + * host controllers.
> + */
> + buf = kmalloc(ARCTIC_REPORT_LEN, GFP_KERNEL);
> + if (!buf)
> + return -ENOMEM;
> +
> + {
> + guard(mutex)(&priv->lock);
> + priv->pwm_duty[channel] = (u8)val;
> + buf[0] = ARCTIC_REPORT_ID;
> + for (i = 0; i < ARCTIC_NUM_FANS; i++)
> + buf[1 + i] = DIV_ROUND_CLOSEST((unsigned int)priv->pwm_duty[i] * 100, 255);
> + }
> + memset(buf + 11, 0, ARCTIC_REPORT_LEN - 11);
> +
> + spin_lock_bh(&priv->in_report_lock);
> + priv->ack_status = -ETIMEDOUT;
> + reinit_completion(&priv->in_report_received);
> + spin_unlock_bh(&priv->in_report_lock);
> +
> + ret = hid_hw_output_report(priv->hdev, buf, ARCTIC_REPORT_LEN);
> + kfree(buf);
> + if (ret < 0)
> + return ret;
> +
> + t = wait_for_completion_interruptible_timeout(&priv->in_report_received,
> + msecs_to_jiffies(ARCTIC_ACK_TIMEOUT_MS));
> + if (t == 0)
> + return -ETIMEDOUT;
> + if (t < 0)
> + return t; /* interrupted by signal */
> + 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_probe(struct hid_device *hdev,
> + const struct hid_device_id *id)
> +{
> + struct arctic_fan_data *priv;
> + struct device *hwmon_dev;
> + 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;
> + mutex_init(&priv->lock);
> + 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;
> +
> + hid_device_io_start(hdev);
> +
> + hwmon_dev = devm_hwmon_device_register_with_info(&hdev->dev, "arctic_fan",
> + priv, &arctic_fan_chip_info,
> + NULL);
> + if (IS_ERR(hwmon_dev)) {
> + ret = PTR_ERR(hwmon_dev);
> + goto out_close;
> + }
> + return 0;
> +
> +out_close:
> + hid_hw_close(hdev);
> +out_stop:
> + hid_hw_stop(hdev);
> + return ret;
> +}
> +
> +static void arctic_fan_remove(struct hid_device *hdev)
> +{
> + 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,
> +};
> +
> +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");
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