Re: Wrongly bound Elantech touchpad on Lenovo Yoga Slim 7

[Jiri Slaby <jirislaby@kernel.org>]

Hi,

I am resuming an ooold thread...

On 05. 02. 22, 12:12, Hans de Goede wrote:
> Hi,
> 
> On 2/4/22 18:39, 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@suse.de> 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).
> 
> Yes I did work on that, but then the other way around making sure
> that the i2c-hid driver would not bind to some devices which need
> the elan_i2c touch*pad* driver.
> 
> And indeed as Dmitry points out:
> 
>> 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.
> 
> I did fix a similar problem for the touchscreen driver last year or so.
> 
> I agree with Dmitry that we should try to avoid DMI matching here;
> and I also agree that having some header with a static inline
> acpi_is_hid_device() device helper would be good.
> 
> I'm a bit worried about the acpi_is_hid_device() approach though,
> there is a lot of copy and pasting going on when vendors create
> ACPI tables and sometimes a "PNP0C50" CID is present combined
> with a valid i2c-hid _DSM method even though the device is not
> an i2c-hid device, also see the i2c_hid_acpi_blacklist[] in
> drivers/hid/i2c-hid/i2c-hid-acpi.c .
> 
> It seems to me that the problem is that the Lenovo Yoga Slim 7
> is using what seems to be a very generic "ELAN0000" ACPI hardware
> id instead of one of the many more specific ones.
> 
> So we could limit the acpi_is_hid_device() check to just the
> "ELAN0000" ACPI hardware id I guess?
> 
> So I see the following 2 options:
> 
> 1. Add an unconditional acpi_is_hid_device() check to elan_probe()
>     and watch out for any bug-reports that this is causing breakage
>     elsehwere
> 2. Add an acpi_is_hid_device() check to elan_probe() for ACPI enumerated
>     touchpads with a hardware-id of ELAN0000 only; and still
>     watch out for any bug-reports that this is causing breakage
>     elsehwere just to be sure

I assume noone ever tried to implement this, right? Or was some 
alternative approach merged in the meantime?

openSUSE still drags the Takashi's downstream patch with a DMI check. It 
would be nice to sort this out upstream and drop that private one ;).

Thanks.

>>> 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@suse.de>
>>> 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@suse.de>
>>> ---
>>>   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
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>
> 
> 

-- 
js
suse labs