[PATCH] HID: wacom: Add Dell Latitude 7275 battery quirk

[PATCH] HID: wacom: Add Dell Latitude 7275 battery quirk

[Jérôme de Bretagne]

The Wacom touchscreen/digitizer in the Dell Latitude 7275
mistakenly reports having a battery, add a quirk to ignore it.

Signed-off-by: Jérôme de Bretagne <jerome.debretagne@gmail.com>
Tested-by: Jérôme de Bretagne <jerome.debretagne@gmail.com>
---
 drivers/hid/wacom_wac.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/hid/wacom_wac.c b/drivers/hid/wacom_wac.c
index 81ba642adcb7..4d4503cbe308 100644
--- a/drivers/hid/wacom_wac.c
+++ b/drivers/hid/wacom_wac.c
@@ -3574,6 +3574,13 @@ void wacom_setup_device_quirks(struct wacom *wacom)
 		__clear_bit(MSC_SERIAL, wacom_wac->pen_input->mscbit);
 		__clear_bit(EV_MSC, wacom_wac->pen_input->evbit);
 	}
+
+	/*
+	 * The Wacom touchscreen/digitizer in the Dell Latitude 7275 mistakenly
+	 * reports having a battery, let's ignore it.
+	 */
+	if (wacom->hdev->product == 0x4804)
+		features->quirks &= ~WACOM_QUIRK_BATTERY;
 }
 
 int wacom_setup_pen_input_capabilities(struct input_dev *input_dev,
-- 
2.30.2

Re: [PATCH] HID: wacom: Add Dell Latitude 7275 battery quirk

[Jérôme de Bretagne]

Le sam. 4 sept. 2021 à 23:25, Jason Gerecke <killertofu@gmail.com> a écrit :
>
> Are you sure that the device is actually unnecessary? Looking online, I believe the 7275 uses an AES sensor which reports the status of the stylus battery when one is in proximity.

Its AES sensor reports the stylus battery level when one is in
proximity indeed. However, I'm not quite sure if this is a kernel API
or a userspace issue but this digitizer device is really confusing as
an end user (within Gnome Settings for instance) :

- it exposes a 0% battery level by default after boot when no stylus
is in proximity (or simply if the user has no stylus at all)
   => it shouldn't display anything at this stage in my opinion

- it exposes a fixed battery level once a stylus is in proximity
(let's say 25%) and it will keep this value until the next reboot,
whether the stylus remains in proximity or not
   => ok, why not

- the above battery level is displayed linked to a device named "Wacom
HID 4804", not obvious that this is the actual battery level of a
recently-used stylus
   => could it report the name of the actual stylus instead? or
something like "Dell Latitude 7275 (Wacom) stylus" at least?

- a connected Bluetooth stylus (an HP Active Pen G2 in my case) will
appear with its own line in the Power settings, somehow duplicating
the "Wacom HID 4804" one
   => should find a way to merge the two lines into one

- the battery level reported by the "HP Active Pen G2" line is
erroneously stuck at 100%
   => not sure yet if this stylus model can report its battery level
on its own via Bluetooth

You can forget about this patch, I'm not convinced anymore this is the
right approach to improve the situation. If you have a better
understanding of the data exposed by the kernel to userspace in these
cases, any pointers for other improvements would be appreciated (in
the kernel or in userspace).

Thanks,
Jérôme

> On Sat, Sep 4, 2021, 2:15 PM Jérôme de Bretagne <jerome.debretagne@gmail.com> wrote:
>>
>> The Wacom touchscreen/digitizer in the Dell Latitude 7275
>> mistakenly reports having a battery, add a quirk to ignore it.
>>
>> Signed-off-by: Jérôme de Bretagne <jerome.debretagne@gmail.com>
>> Tested-by: Jérôme de Bretagne <jerome.debretagne@gmail.com>
>> ---
>>  drivers/hid/wacom_wac.c | 7 +++++++
>>  1 file changed, 7 insertions(+)
>>
>> diff --git a/drivers/hid/wacom_wac.c b/drivers/hid/wacom_wac.c
>> index 81ba642adcb7..4d4503cbe308 100644
>> --- a/drivers/hid/wacom_wac.c
>> +++ b/drivers/hid/wacom_wac.c
>> @@ -3574,6 +3574,13 @@ void wacom_setup_device_quirks(struct wacom *wacom)
>>                 __clear_bit(MSC_SERIAL, wacom_wac->pen_input->mscbit);
>>                 __clear_bit(EV_MSC, wacom_wac->pen_input->evbit);
>>         }
>> +
>> +       /*
>> +        * The Wacom touchscreen/digitizer in the Dell Latitude 7275 mistakenly
>> +        * reports having a battery, let's ignore it.
>> +        */
>> +       if (wacom->hdev->product == 0x4804)
>> +               features->quirks &= ~WACOM_QUIRK_BATTERY;
>>  }
>>
>>  int wacom_setup_pen_input_capabilities(struct input_dev *input_dev,
>> --
>> 2.30.2
>>

Re: [PATCH] HID: wacom: Add Dell Latitude 7275 battery quirk

[Filipe Laíns]

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On Sat, 2021-09-04 at 22:58 +0200, Jérôme de Bretagne wrote:
> The Wacom touchscreen/digitizer in the Dell Latitude 7275
> mistakenly reports having a battery, add a quirk to ignore it.
> 
> Signed-off-by: Jérôme de Bretagne <jerome.debretagne@gmail.com>
> Tested-by: Jérôme de Bretagne <jerome.debretagne@gmail.com>
> ---
>  drivers/hid/wacom_wac.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/hid/wacom_wac.c b/drivers/hid/wacom_wac.c
> index 81ba642adcb7..4d4503cbe308 100644
> --- a/drivers/hid/wacom_wac.c
> +++ b/drivers/hid/wacom_wac.c
> @@ -3574,6 +3574,13 @@ void wacom_setup_device_quirks(struct wacom *wacom)
>                 __clear_bit(MSC_SERIAL, wacom_wac->pen_input->mscbit);
>                 __clear_bit(EV_MSC, wacom_wac->pen_input->evbit);
>         }
> +
> +       /*
> +        * The Wacom touchscreen/digitizer in the Dell Latitude 7275
> mistakenly
> +        * reports having a battery, let's ignore it.
> +        */
> +       if (wacom->hdev->product == 0x4804)

We probably want a define for this ID.

> +               features->quirks &= ~WACOM_QUIRK_BATTERY;
>  }
>  
>  int wacom_setup_pen_input_capabilities(struct input_dev *input_dev,

Cheers,
Filipe Laíns

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