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([2600:1700:e321:62f0:da43:aeff:fecc:bfd5]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-c76c657e5f3sm411519a12.23.2026.04.01.10.34.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 01 Apr 2026 10:34:32 -0700 (PDT) Sender: Guenter Roeck Message-ID: <03b32c90-7b62-47d0-9422-4f0f5dd0df29@roeck-us.net> Date: Wed, 1 Apr 2026 10:34:30 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6] hwmon: add driver for ARCTIC Fan Controller To: Aureo Serrano de Souza , linux-hwmon@vger.kernel.org Cc: linux@weissschuh.net, corbet@lwn.net, skhan@linuxfoundation.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260401153949.77488-1-aureo.serrano@arctic.de> Content-Language: en-US From: Guenter Roeck Autocrypt: addr=linux@roeck-us.net; keydata= xsFNBE6H1WcBEACu6jIcw5kZ5dGeJ7E7B2uweQR/4FGxH10/H1O1+ApmcQ9i87XdZQiB9cpN RYHA7RCEK2dh6dDccykQk3bC90xXMPg+O3R+C/SkwcnUak1UZaeK/SwQbq/t0tkMzYDRxfJ7 nyFiKxUehbNF3r9qlJgPqONwX5vJy4/GvDHdddSCxV41P/ejsZ8PykxyJs98UWhF54tGRWFl 7i1xvaDB9lN5WTLRKSO7wICuLiSz5WZHXMkyF4d+/O5ll7yz/o/JxK5vO/sduYDIlFTvBZDh gzaEtNf5tQjsjG4io8E0Yq0ViobLkS2RTNZT8ICq/Jmvl0SpbHRvYwa2DhNsK0YjHFQBB0FX IdhdUEzNefcNcYvqigJpdICoP2e4yJSyflHFO4dr0OrdnGLe1Zi/8Xo/2+M1dSSEt196rXaC kwu2KgIgmkRBb3cp2vIBBIIowU8W3qC1+w+RdMUrZxKGWJ3juwcgveJlzMpMZNyM1jobSXZ0 VHGMNJ3MwXlrEFPXaYJgibcg6brM6wGfX/LBvc/haWw4yO24lT5eitm4UBdIy9pKkKmHHh7s jfZJkB5fWKVdoCv/omy6UyH6ykLOPFugl+hVL2Prf8xrXuZe1CMS7ID9Lc8FaL1ROIN/W8Vk BIsJMaWOhks//7d92Uf3EArDlDShwR2+D+AMon8NULuLBHiEUQARAQABzTJHdWVudGVyIFJv ZWNrIChMaW51eCBhY2NvdW50KSA8bGludXhAcm9lY2stdXMubmV0PsLBgQQTAQIAKwIbAwYL CQgHAwIGFQgCCQoLBBYCAwECHgECF4ACGQEFAmgrMyQFCSbODQkACgkQyx8mb86fmYGcWRAA oRwrk7V8fULqnGGpBIjp7pvR187Yzx+lhMGUHuM5H56TFEqeVwCMLWB2x1YRolYbY4MEFlQg VUFcfeW0OknSr1s6wtrtQm0gdkolM8OcCL9ptTHOg1mmXa4YpW8QJiL0AVtbpE9BroeWGl9v 2TGILPm9mVp+GmMQgkNeCS7Jonq5f5pDUGumAMguWzMFEg+Imt9wr2YA7aGen7KPSqJeQPpj onPKhu7O/KJKkuC50ylxizHzmGx+IUSmOZxN950pZUFvVZH9CwhAAl+NYUtcF5ry/uSYG2U7 DCvpzqOryJRemKN63qt1bjF6cltsXwxjKOw6CvdjJYA3n6xCWLuJ6yk6CAy1Ukh545NhgBAs rGGVkl6TUBi0ixL3EF3RWLa9IMDcHN32r7OBhw6vbul8HqyTFZWY2ksTvlTl+qG3zV6AJuzT WdXmbcKN+TdhO5XlxVlbZoCm7ViBj1+PvIFQZCnLAhqSd/DJlhaq8fFXx1dCUPgQDcD+wo65 qulV/NijfU8bzFfEPgYP/3LP+BSAyFs33y/mdP8kbMxSCjnLEhimQMrSSo/To1Gxp5C97fw5 3m1CaMILGKCmfI1B8iA8zd8ib7t1Rg0qCwcAnvsM36SkrID32GfFbv873bNskJCHAISK3Xkz qo7IYZmjk/IJGbsiGzxUhvicwkgKE9r7a1rOwU0ETofVZwEQALlLbQeBDTDbwQYrj0gbx3bq 7kpKABxN2MqeuqGr02DpS9883d/t7ontxasXoEz2GTioevvRmllJlPQERVxM8gQoNg22twF7 pB/zsrIjxkE9heE4wYfN1AyzT+AxgYN6f8hVQ7Nrc9XgZZe+8IkuW/Nf64KzNJXnSH4u6nJM J2+Dt274YoFcXR1nG76Q259mKwzbCukKbd6piL+VsT/qBrLhZe9Ivbjq5WMdkQKnP7gYKCAi pNVJC4enWfivZsYupMd9qn7Uv/oCZDYoBTdMSBUblaLMwlcjnPpOYK5rfHvC4opxl+P/Vzyz 6WC2TLkPtKvYvXmdsI6rnEI4Uucg0Au/Ulg7aqqKhzGPIbVaL+U0Wk82nz6hz+WP2ggTrY1w ZlPlRt8WM9w6WfLf2j+PuGklj37m+KvaOEfLsF1v464dSpy1tQVHhhp8LFTxh/6RWkRIR2uF I4v3Xu/k5D0LhaZHpQ4C+xKsQxpTGuYh2tnRaRL14YMW1dlI3HfeB2gj7Yc8XdHh9vkpPyuT nY/ZsFbnvBtiw7GchKKri2gDhRb2QNNDyBnQn5mRFw7CyuFclAksOdV/sdpQnYlYcRQWOUGY HhQ5eqTRZjm9z+qQe/T0HQpmiPTqQcIaG/edgKVTUjITfA7AJMKLQHgp04Vylb+G6jocnQQX JqvvP09whbqrABEBAAHCwWUEGAECAA8CGwwFAmgrMyQFCSbODQkACgkQyx8mb86fmYHlgg/9 H5JeDmB4jsreE9Bn621wZk7NMzxy9STxiVKSh8Mq4pb+IDu1RU2iLyetCY1TiJlcxnE362kj njrfAdqyPteHM+LU59NtEbGwrfcXdQoh4XdMuPA5ADetPLma3YiRa3VsVkLwpnR7ilgwQw6u dycEaOxQ7LUXCs0JaGVVP25Z2hMkHBwx6BlW6EZLNgzGI2rswSZ7SKcsBd1IRHVf0miwIFYy j/UEfAFNW+tbtKPNn3xZTLs3quQN7GdYLh+J0XxITpBZaFOpwEKV+VS36pSLnNl0T5wm0E/y scPJ0OVY7ly5Vm1nnoH4licaU5Y1nSkFR/j2douI5P7Cj687WuNMC6CcFd6j72kRfxklOqXw zvy+2NEcXyziiLXp84130yxAKXfluax9sZhhrhKT6VrD45S6N3HxJpXQ/RY/EX35neH2/F7B RgSloce2+zWfpELyS1qRkCUTt1tlGV2p+y2BPfXzrHn2vxvbhEn1QpQ6t+85FKN8YEhJEygJ F0WaMvQMNrk9UAUziVcUkLU52NS9SXqpVg8vgrO0JKx97IXFPcNh0DWsSj/0Y8HO/RDkGXYn FDMj7fZSPKyPQPmEHg+W/KzxSSfdgWIHF2QaQ0b2q1wOSec4Rti52ohmNSY+KNIW/zODhugJ np3900V20aS7eD9K8GTU0TGC1pyz6IVJwIE= In-Reply-To: <20260401153949.77488-1-aureo.serrano@arctic.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 4/1/26 08:39, 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 This must be a resend because it does not appear to be corrupted. Please mention that in the future. Sashiko still has a couple of comments: https://sashiko.dev/#/patchset/20260401153949.77488-1-aureo.serrano%40arctic.de Ignore the cache line comment. The concern about the redundant hid_device_io_stop() seems real, though. Please check. Thanks, Guenter > --- > 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 > + > +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 > +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 > M: Krzysztof Kozlowski > 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 +1,370 @@ > +// 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 > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > + > +#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 "); > +MODULE_DESCRIPTION("HID hwmon driver for ARCTIC Fan Controller"); > +MODULE_LICENSE("GPL");