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Sat, 09 May 2026 08:43:21 -0700 (PDT) Sender: Guenter Roeck Date: Sat, 9 May 2026 08:43:20 -0700 From: Guenter Roeck To: Aureo Serrano de Souza Cc: linux-hwmon@vger.kernel.org, linux@weissschuh.net, corbet@lwn.net, skhan@linuxfoundation.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v7 RESEND] hwmon: add driver for ARCTIC Fan Controller Message-ID: <839d67bb-79fe-4096-965f-ead57112b3a3@roeck-us.net> References: <20260508064405.38676-1-aureo.serrano@arctic.de> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260508064405.38676-1-aureo.serrano@arctic.de> On Fri, May 08, 2026 at 02:44:00PM +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 I guess we can live with the potential 1-second sysfs read stall on driver unload reported by Sashiko. Applied. Thanks, Guenter