linux-kernel - Re: [PATCH v6 0/7] HID: asus: Fix ASUS ROG Laptop's Keyboard backlight handling

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Message-ID: <18bb12d2-c258-5064-1702-005f9d5b0dd3@linux.intel.com>
Date: Fri, 17 Oct 2025 13:36:04 +0300 (EEST)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Antheas Kapenekakis <lkml@...heas.dev>
cc: Denis Benato <benato.denis96@...il.com>, 
    platform-driver-x86@...r.kernel.org, linux-input@...r.kernel.org, 
    LKML <linux-kernel@...r.kernel.org>, Jiri Kosina <jikos@...nel.org>, 
    Benjamin Tissoires <bentiss@...nel.org>, 
    Corentin Chary <corentin.chary@...il.com>, 
    "Luke D . Jones" <luke@...nes.dev>, Hans de Goede <hdegoede@...hat.com>
Subject: Re: [PATCH v6 0/7] HID: asus: Fix ASUS ROG Laptop's Keyboard backlight
 handling

On Thu, 16 Oct 2025, Antheas Kapenekakis wrote:
> On Thu, 16 Oct 2025 at 17:09, Ilpo Järvinen
> > On Thu, 16 Oct 2025, Antheas Kapenekakis wrote:
> > > On Thu, 16 Oct 2025 at 13:57, Denis Benato <benato.denis96@...il.com> wrote:
> > > > On 10/13/25 22:15, Antheas Kapenekakis wrote:
> > > > > This is a two part series which does the following:
> > > > >   - Clean-up init sequence
> > > > >   - Unify backlight handling to happen under asus-wmi so that all Aura
> > > > >     devices have synced brightness controls and the backlight button works
> > > > >     properly when it is on a USB laptop keyboard instead of one w/ WMI.
> > > > >
> > > > > For more context, see cover letter of V1. Since V5, I removed some patches
> > > > > to make this easier to merge.
> > > > >
> > > > > All comments with these patches had been addressed since V4.
> > > > I have loaded this patchset for users of asus-linux project to try out.
> > > >
> > > > One of them opened a bug report about a kernel bug that happens
> > > > consistently when closing the lid of his laptop [1].
> > > >
> > > > He also sent another piece of kernel log, but didn't specify anything more
> > > > about this [2].
> > > >
> > > > [1] https://pastebin.com/akZx1w10
> > > > [2] https://pastebin.com/sKdczPgf
> > >
> > > Can you provide a link to the bug report? [2] seems unrelated.
> > >
> > > As for [1], it looks like a trace that stems from a sysfs write to
> > > brightness stemming from userspace that follows the same chain it
> > > would on a stock kernel and times out. Is it present on a stock
> > > kernel?
> > >
> > > Ilpo should know more about this, could the spinlock be interfering?
> >
> > [1] certainly seems to do schedule() from do_kbd_led_set() so it's not
> > possible to use spinlock there.
> >
> > So we're back to what requires the spinlock? And what the spinlock
> > protects?
> 
> For that invocation, since it is coming from the cdev device owned by
> asus_wmi, it protects asus_ref.listeners under do_kbd_led_set.
> asus_wmi is protected by the fact it is owned by that device. Spinlock
> is not required in this invocation due to not being an IRQ.
> 
> Under asus_hid_event (second to last patch), which is called from an
> IRQ, a spinlock is required for protecting both listeners and the
> asus_ref.asus, and I suspect that scheduling from an IRQ is not
> allowed either. Is that correct?

Yes, it's not allowed either.

hid-asus seems to already use workqueue (though include for it is 
missing) likely to workaround a similar challenge.

-- 
 i.