Re: Wrongly bound Elantech touchpad on Lenovo Yoga Slim 7

[Dmitry Torokhov]

Hi Benjamin,

On Fri, Feb 04, 2022 at 06:39:40PM +0100, Benjamin Tissoires wrote:
> Hi,
> 
> [adding Dmitry, the maintainer of the input tree and Hans, a colleague of mine]
> 
> On Fri, Feb 4, 2022 at 5:57 PM Takashi Iwai <tiwai@xxxxxxx> wrote:
> >
> > Hi,
> >
> > we've got a bug report on openSUSE Bugzilla about the broken touchpad
> > on Lenovo Yoga Slim 7:
> >   https://bugzilla.opensuse.org/show_bug.cgi?id=1193064
> >
> > The touchpad is an Elantech one, connected over i2c, and there are two
> > drivers supporting it.  Unfortunately, the default one the system
> > binds, elan-i2c input driver, doesn't seem working properly, while
> > i2c-hid driver works.
> 
> Hans, we do have a similar bug on RHEL at
> https://bugzilla.redhat.com/show_bug.cgi?id=2029078 (sorry, private
> bug).
> 
> IIRC you worked on the discrimination between i2c-hid and elan_i2c (I
> might be completely wrong though).
> Would this patch be OK with you?

I would prefer avoid DMI if possible.

I believe we need to do what Hans did for Elan Touch*screen* driver and
avoid binding to the device if it has i2c-hid-specific _DMS in ACPI.
I.e. we need to replicate elants_acpi_is_hid_device().

Even better would be to factor it out, maybe not into a shared module
but simply shared header with static inline function that we could share
between elan drivers and maybe others as well.

Thanks.

> 
> Cheers,
> Benjamin
> 
> >
> > I'm not sure what's the best fix for this, but below a quick
> > workaround using a deny list with DMI matching.
> > If this is OK, I can resubmit the patch for merging.
> >
> > Any comments appreciated.
> >
> >
> > thanks,
> >
> > Takashi
> >
> > -- 8< --
> > From: Takashi Iwai <tiwai@xxxxxxx>
> > Subject: [PATCH] Input: elan_i2c: Add deny list for Lenovo Yoga Slim 7
> >
> > The touchpad on Lenovo Yoga Slim 7 doesn't work well with elan-i2c but
> > rather better with i2c-hid.  Add a deny list for avoiding to bind with
> > elan-i2c.
> >
> > BugLink: https://bugzilla.opensuse.org/show_bug.cgi?id=1193064
> > Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
> > ---
> >  drivers/input/mouse/elan_i2c_core.c | 19 +++++++++++++++++++
> >  1 file changed, 19 insertions(+)
> >
> > diff --git a/drivers/input/mouse/elan_i2c_core.c b/drivers/input/mouse/elan_i2c_core.c
> > index 47af62c12267..fd08481f7aea 100644
> > --- a/drivers/input/mouse/elan_i2c_core.c
> > +++ b/drivers/input/mouse/elan_i2c_core.c
> > @@ -18,6 +18,7 @@
> >  #include <linux/acpi.h>
> >  #include <linux/delay.h>
> >  #include <linux/device.h>
> > +#include <linux/dmi.h>
> >  #include <linux/firmware.h>
> >  #include <linux/i2c.h>
> >  #include <linux/init.h>
> > @@ -1222,6 +1223,20 @@ static void elan_disable_regulator(void *_data)
> >         regulator_disable(data->vcc);
> >  }
> >
> > +static const struct dmi_system_id elan_i2c_denylist[] __initconst = {
> > +#if IS_ENABLED(CONFIG_I2C_HID_ACPI)
> > +       {
> > +               /* Lenovo Yoga Slim 7 is better supported by i2c-hid */
> > +               .matches = {
> > +                       DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
> > +                       DMI_MATCH(DMI_PRODUCT_NAME, "82A3"),
> > +                       DMI_MATCH(DMI_PRODUCT_VERSION, "Yoga Slim 7 14ITL05"),
> > +               },
> > +       },
> > +#endif
> > +       { }
> > +};
> > +
> >  static int elan_probe(struct i2c_client *client,
> >                       const struct i2c_device_id *dev_id)
> >  {
> > @@ -1233,6 +1248,10 @@ static int elan_probe(struct i2c_client *client,
> >
> >         if (IS_ENABLED(CONFIG_MOUSE_ELAN_I2C_I2C) &&
> >             i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
> > +               if (dmi_check_system(elan_i2c_denylist)) {
> > +                       dev_info(dev, "Hits deny list, skipping\n");
> > +                       return -ENODEV;
> > +               }
> >                 transport_ops = &elan_i2c_ops;
> >         } else if (IS_ENABLED(CONFIG_MOUSE_ELAN_I2C_SMBUS) &&
> >                    i2c_check_functionality(client->adapter,
> > --
> > 2.31.1
> >
> >
> >
> >
> >
> >
> >
> 

-- 
Dmitry