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Date:   Wed, 04 Oct 2023 19:33:01 -0700
From:   Rain <rain@sunshowers.io>
To:     "Rahul Rameshbabu" <sergeantsagara@protonmail.com>
Cc:     "Jiri Kosina" <jikos@kernel.org>,
        "Benjamin Tissoires" <benjamin.tissoires@redhat.com>,
        "Henrik Rydberg" <rydberg@bitmath.org>,
        linux-input@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] HID: multitouch: Add required quirk for Synaptics 0xcd7e device
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On Wed, Oct 4, 2023, at 19:29, Rahul Rameshbabu wrote:
> On Wed, 04 Oct, 2023 12:01:27 -0700 "Rain" <rain@sunshowers.io> wrote:
>> On Sun, Sep 17, 2023, at 09:18, Rahul Rameshbabu wrote:
>>> Register the Synaptics device as a special multitouch device with certain
>>> quirks that may improve usability of the touchpad device.
>>>
>>> Reported-by: Rain <rain@sunshowers.io>
>>> Closes:
>>> https://lore.kernel.org/linux-input/2bbb8e1d-1793-4df1-810f-cb0137341ff4@app.fastmail.com/
>>> Signed-off-by: Rahul Rameshbabu <sergeantsagara@protonmail.com>
>>> ---
>>>
>>> Notes:
>>>     Theory:
>>>
>>>       I think the Synaptics device in the related email to the linux-input
>>>       mailing list requires certain quirks like MT_QUIRK_HOVERING to correctly
>>>       reconfigure the distance configuration for multitouch events. This might
>>>       explain why light touches were not registered originally when
>>>       MT_CLS_DEFAULT was used by default for the device. Would like to have
>>>       this patch tested before being merged. A Tested-by: git trailer can then
>>>       be appended.
>>>
>>>  drivers/hid/hid-multitouch.c | 4 ++++
>>>  1 file changed, 4 insertions(+)
>>>
>>> diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
>>> index 521b2ffb4244..8db4ae05febc 100644
>>> --- a/drivers/hid/hid-multitouch.c
>>> +++ b/drivers/hid/hid-multitouch.c
>>> @@ -2144,6 +2144,10 @@ static const struct hid_device_id mt_devices[] = {
>>>  			USB_DEVICE_ID_MTP_STM)},
>>>
>>>  	/* Synaptics devices */
>>> +	{ .driver_data = MT_CLS_WIN_8_FORCE_MULTI_INPUT,
>>> +		HID_DEVICE(BUS_I2C, HID_GROUP_MULTITOUCH_WIN_8,
>>> +			USB_VENDOR_ID_SYNAPTICS, 0xcd7e) },
>>
>> Thanks for the patch! I haven't tested it yet but it looks promising.
>>
>> The vendor ID isn't USB_VENDOR_ID_SYNAPTICS (0x06cb),
>> however -- it's SYNA7DB5 (0x7db5) which I guess is an alternative vendor
>> ID for Synaptics. Would be worth fixing that.
>
> Hi Rain,
>
> I think you might be confusing the device name string with the vendor
> id, based on my interpretation of the output you shared.
>
>   [    2.034760] input: SYNA7DB5:00 06CB:CD7E Mouse as 
> /devices/platform/AMDI0010:00/i2c-0/i2c-SYNA7DB5:00/0018:06CB:CD7E.0001/input/input1
>   [    2.034865] input: SYNA7DB5:00 06CB:CD7E Touchpad as 
> /devices/platform/AMDI0010:00/i2c-0/i2c-SYNA7DB5:00/0018:06CB:CD7E.0001/input/input2
>
> The first column has a device name but what we are interested in is the
> second column, '06CB:CD7E'. 0x06CB is the vendor id and 0xCD7E is the
> device id. Hope that makes sense and let me know if you think this is
> off.

Ah, got it, thank you! I was definitely misreading what was going on and
was a bit thrown off by the "SYNA7DB5". Sorry about the confusion.

> In general for these types of issues, I think the right direction would
> be to make quirks loadable in userspace through HID-BPF where DEs or
> some systemd subsystem can help users load quirks needed for their HID
> devices rather than building a list of quirks in the driver. This is
> something I am interested in exploring.

That would definitely be very interesting.

Thanks again for the fix.