linux-kernel - Re: [PATCH v2 2/2] HID: multitouch: Toggle touch surface on Elan touchpad on lid event

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <v24zlqrmvov4gdjoa2xa7qv353pilgq2d6ag6nprgeue7tai4f@a4i632p5fbme>
Date: Mon, 17 Nov 2025 23:12:00 -0800
From: Dmitry Torokhov <dmitry.torokhov@...il.com>
To: Jonathan Denose <jdenose@...gle.com>
Cc: Jiri Kosina <jikos@...nel.org>, 
	Benjamin Tissoires <bentiss@...nel.org>, linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] HID: multitouch: Toggle touch surface on Elan
 touchpad on lid event

On Wed, Nov 12, 2025 at 05:49:53PM -0600, Jonathan Denose wrote:
> Hi Dmitry,
> 
> Thanks for your review.
> 
> On Tue, Nov 11, 2025 at 4:37 PM Dmitry Torokhov
> <dmitry.torokhov@...il.com> wrote:
> >
> > Hi Jonathan,
> >
> > On Tue, Nov 11, 2025 at 09:34:07PM +0000, Jonathan Denose wrote:
> > > Many touchpad modules have a pin which is expected to be connected to the
> > > lid angle sensor in laptops. The pin sends a signal to the touchpad module
> > > about the lid state and each touchpad vendor handles this notification in
> > > their firmware.
> > >
> > > The Elan touchpad with VID 323b does not always have this aforementioned
> > > pin, which then causes interference between the lid and the touchpad when
> > > the lid is closed. This interference causes a few seconds delay before the
> > > touchpad works again, or it causes it to be come completely unresponsive.
> > > To circumvent this hardware issue in software, implement a device quirk
> > > which will allow the hid-multitouch driver to register a notifier_block
> > > to listen for lid switch events. When the lid switch closes, the
> > > touchpad surface will be turned off and when the lid switch opens, the
> > > touchpad surgace will be turned on. This triggers recalibration which
> > > resolves interference issues when the lid is closed.
> > >
> > > Signed-off-by: Jonathan Denose <jdenose@...gle.com>
> > > ---
> > >  drivers/hid/hid-multitouch.c | 32 +++++++++++++++++++++++++++++++-
> > >  1 file changed, 31 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
> > > index 2879e65cf303b1456311ac06115adda5a78a2600..9a89913c193bc110a0a821a901aebd97892c66bd 100644
> > > --- a/drivers/hid/hid-multitouch.c
> > > +++ b/drivers/hid/hid-multitouch.c
> > > @@ -35,6 +35,7 @@
> > >  #include <linux/device.h>
> > >  #include <linux/hid.h>
> > >  #include <linux/module.h>
> > > +#include <linux/notifier.h>
> > >  #include <linux/slab.h>
> > >  #include <linux/input/mt.h>
> > >  #include <linux/jiffies.h>
> > > @@ -76,6 +77,7 @@ MODULE_LICENSE("GPL");
> > >  #define MT_QUIRK_DISABLE_WAKEUP              BIT(21)
> > >  #define MT_QUIRK_ORIENTATION_INVERT  BIT(22)
> > >  #define MT_QUIRK_APPLE_TOUCHBAR              BIT(23)
> > > +#define MT_QUIRK_REGISTER_LID_NOTIFIER BIT(24)
> > >
> > >  #define MT_INPUTMODE_TOUCHSCREEN     0x02
> > >  #define MT_INPUTMODE_TOUCHPAD                0x03
> > > @@ -183,6 +185,8 @@ struct mt_device {
> > >       struct list_head reports;
> > >  };
> > >
> > > +static struct hid_device *lid_notify_hdev;
> >
> > This should really be per-device.
> 
> Just to be sure I'm following correctly, the initialization of
> lid_notify_hdev should be per-device?

Yes. I believe this is the best practice.

Thanks.

-- 
Dmitry