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SubjectRe: Query regarding hid-multitouch.c driver in 4.14/4.19
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Hi Benjamin,

Thanks for taking a look at it and providing your inputs. We will check
in the direction suggested by you. I was off from work for some time, so
couldn't reply earlier.


Thanks
Neeraj

On 11/22/2019 2:55 PM, Benjamin Tissoires wrote:
> Hi Neeraj,
>
> On Fri, Nov 22, 2019 at 5:42 AM Neeraj Upadhyay <neeraju@codeaurora.org> wrote:
>>
>> Hi Benjamin,
>>
>> Can you please provide guidance on how to workaround this problem? Is it
>> possible to support the 4.14 kernel behaviour again, so that existing
>> clients are not impacted?
>
> Hmm, hard to say. Both evdev outputs from 4.14 and 4.19 are
> technically valid. So I guess the issue is more that the android
> version you are using is not interpreting correctly the 4.19 event
> stream and probably requires some more events (like pressure or
> width/height).
>
> Also, the report descriptor is crap:
>
> 0x05, 0x0d, // Usage Page (Digitizers) 0
> 0x09, 0x02, // Usage (Pen) 2
> 0xa1, 0x01, // Collection (Application) 4
> 0x85, 0x01, // Report ID (1) 6
> 0x09, 0x22, // Usage (Finger) 8
> 0xa1, 0x02, // Collection (Logical) 10
> 0x09, 0x42, // Usage (Tip Switch) 12
> 0x15, 0x00, // Logical Minimum (0) 14
> 0x25, 0x01, // Logical Maximum (1) 16
> 0x75, 0x01, // Report Size (1) 18
> 0x95, 0x01, // Report Count (1) 20
> 0x81, 0x02, // Input (Data,Var,Abs) 22
> 0x09, 0x32, // Usage (In Range) 24
> 0x81, 0x02, // Input (Data,Var,Abs) 26
> 0x95, 0x06, // Report Count (6) 28
> 0x81, 0x03, // Input (Cnst,Var,Abs) 30
> 0x75, 0x08, // Report Size (8) 32
> 0x09, 0x51, // Usage (Contact Id) 34
> 0x95, 0x01, // Report Count (1) 36
> 0x81, 0x02, // Input (Data,Var,Abs) 38
> 0x05, 0x01, // Usage Page (Generic Desktop) 40
> 0x26, 0xff, 0x0f, // Logical Maximum (4095) 42
> 0x75, 0x10, // Report Size (16) 45
> 0x55, 0x0e, // Unit Exponent (-2) 47
> 0x65, 0x33, // Unit (Inch^3,EngLinear) 49
> 0x09, 0x30, // Usage (X) 51
> 0x35, 0x00, // Physical Minimum (0) 53
> 0x46, 0xb5, 0x04, // Physical Maximum (1205) 55
> 0x81, 0x02, // Input (Data,Var,Abs) 58
> 0x46, 0x8a, 0x03, // Physical Maximum (906) 60
> 0x09, 0x31, // Usage (Y) 63
> 0x81, 0x02, // Input (Data,Var,Abs) 65
> 0xc0, // End Collection 67
> 0x05, 0x0d, // Usage Page (Digitizers) 68
> 0x09, 0x54, // Usage (Contact Count) 70
> 0x95, 0x01, // Report Count (1) 72
> 0x75, 0x08, // Report Size (8) 74
> 0x81, 0x02, // Input (Data,Var,Abs) 76
> 0x85, 0x08, // Report ID (8) 78
> 0x09, 0x55, // Usage (Contact Max) 80
> 0x25, 0x05, // Logical Maximum (5) 82
> 0xb1, 0x02, // Feature (Data,Var,Abs) 84
> 0xc0, // End Collection 86
> 0x05, 0x0c, // Usage Page (Consumer Devices) 87
> 0x09, 0x01, // Usage (Consumer Control) 89
> 0xa1, 0x01, // Collection (Application) 91
> 0x85, 0x02, // Report ID (2) 93
> 0x09, 0xe9, // Usage (Volume Up) 95
> 0x09, 0xea, // Usage (Volume Down) 97
> 0x0a, 0xae, 0x01, // Usage (AL Keyboard Layout) 99
> 0x09, 0xe2, // Usage (Mute) 102
> 0x09, 0x30, // Usage (Power) 104
> 0x15, 0x01, // Logical Minimum (1) 106
> 0x25, 0x0c, // Logical Maximum (12) 108
> 0x75, 0x10, // Report Size (16) 110
> 0x95, 0x01, // Report Count (1) 112
> 0x81, 0x00, // Input (Data,Arr,Abs) 114
> 0xc0, // End Collection 116
>
> It declares right at the beginning a Pen application collection then a
> Finger logical application. This should never happen as you can not
> use a pen with a bare finger.
>
> Anyway, there are a few things you could do to solve the issue,
> depending on what you are allowed to do:
> - if you can tweak the kernel, then maybe adding an extra kernel
> module that just binds to the device without changing anything in
> probe or in events might do the trick. For extra safety you should
> probably fix the report descriptor in this new kernel module
> - if you can tweak bluez or the device itself, at least change the
> ContactID usage to 00 (byte offset 35 above: change 0x51 to 0x00). It
> would be best to actually change the whole report descriptor with the
> correct applications, but, meh, this seems to be working.
> - if you can tweak android, then ensure it can understand this
> particular event stream
>
> Anyway, I don't think this is an upstream problem, as the device
> behaves somehow correctly by 5.3, at least it sends me the events I
> expect. So I can't really spend a lot of time providing a workaround
> for that.
>
> My best bet would be to contact the device maker, and ask them to fix
> their device to be working with 4.19 kernel.
>
> Cheers,
> Benjamin
>
>>
>>
>> Thanks
>> Neeraj
>>
>> On 11/14/2019 10:01 AM, Neeraj Upadhyay wrote:
>>> Hi Benjamin,
>>>
>>> Sorry for the delay, was waiting for the required information from our
>>> team.
>>>
>>> On 11/13/2019 3:00 PM, Benjamin Tissoires wrote:
>>>> Hi Neeraj,
>>>>
>>>> On Wed, Nov 13, 2019 at 4:11 AM Neeraj Upadhyay
>>>> <neeraju@codeaurora.org> wrote:
>>>>> Hi,
>>>>>
>>>>> I have one query regarding hid-multitouch.c driver and need your
>>>>> guidance on
>>>>> how hid-multitouchc can restore/support the original behaviour,
>>>>> where, for
>>>>> devices, for which application is not
>>>>> HID_DG_TOUCHSCREEN/HID_DG_TOUCHPAD, and has
>>>>> HID_DG_CONTACTID usage in its report, can still use generic input
>>>>> mappings.
>>>>>
>>>>> We are using kernel versions 4.14 , 4.19 respectively in 2 different
>>>>> projects:
>>>>>
>>>>> 4.14:
>>>>> https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/drivers/hid/hid-multitouch.c?h=v4.14.153
>>>>>
>>>>> 4.19:
>>>>> https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/drivers/hid/hid-multitouch.c?h=v4.19.83
>>>>>
>>>>>
>>>>> I checked the application for our hid device, it's HID_DG_PEN, device
>>>>> also has a HID_DG_CONTACTID usage defined in
>>>>>
>>>>> its report.
>>>>>
>>>>> In 4.19, is_mt_collection is set to 'true'. All multitouch code paths or
>>>>> input mapping is configured
>>>>>
>>>>> mt_allocate_report_data()
>>>>> ...
>>>>> for (n = 0; n < field->report_count; n++) {
>>>>> if (field->usage[n].hid == HID_DG_CONTACTID)
>>>>> rdata->is_mt_collection = true; //
>>>>> is_mt_collection is set to 'true'
>>>>> }
>>>>> }
>>>>>
>>>>> mt_input_mapping()
>>>>> ...
>>>>> if (rdata->is_mt_collection)
>>>>> return mt_touch_input_mapping(...) //
>>>>> mt_touch_input_mapping() is called
>>>>>
>>>>> mt_event()
>>>>> if (rdata && rdata->is_mt_collection)
>>>>> return mt_touch_event(); // mt_touch_event() is called
>>>>>
>>>>> However, in 4.14, the behaviour was different, mt input mapping was done
>>>>> only
>>>>> for HID_DG_TOUCHSCREEN/HID_DG_TOUCHPAD , and because our hid device is
>>>>> HID_DG_PEN, generic mappings were applied for it; with these settings,
>>>>> device
>>>>> responds to events.
>>>>>
>>>>> static int mt_input_mapping()
>>>>> if (field->application == HID_DG_TOUCHSCREEN ||
>>>>> field->application == HID_DG_TOUCHPAD)
>>>>> return mt_touch_input_mapping(); // This is not called.
>>>>>
>>>>>
>>>>> mt_touch_input_mapping()
>>>>> case HID_DG_CONTACTID:
>>>>> mt_store_field(usage, td, hi);
>>>>> td->touches_by_report++;
>>>>> td->mt_report_id = field->report->id; //
>>>>> mt_report_id is not set.
>>>>> return 1;
>>>>>
>>>>>
>>>>> Looks like this behaviour changed, with below commits:
>>>>>
>>>>> https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/drivers/hid/hid-multitouch.c?h=v4.19.83&id=8dfe14b3b47ff832cb638731f9fc696a3a84f804
>>>>>
>>>>> 8dfe14b3b47f HID: multitouch: ditch mt_report_id
>>>>> https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/drivers/hid/hid-multitouch.c?h=v4.19.83&id=ba6b055e0f3b4ff4942e4ab273260affcfad9bff
>>>>>
>>>>> ba6b055e0f3b HID: input: enable Totem on the Dell Canvas 27
>>>>>
>>>>> Can you please suggest on how we can support/preserve the original
>>>>> behaviour?
>>>> Hmm, I would initially say that a firmware that exports Contact ID for
>>>> a Pen is definitely wrong. The Contact ID usage has been introduced in
>>>> https://www.usb.org/sites/default/files/hutrr34.pdf and is
>>>> specifically for multi-touch, not multi pen.
>>>>
>>>> Anyway, couple of questions:
>>>> - does the device supports multi-pen?
>>>
>>> Actually the device is a selfie stick device:
>>> https://item.jd.com/33082497741.html
>>>
>>> It does not support multi-pen.
>>>
>>>> - can you share the report descriptor and a few events when triggering
>>>> this particular report (ideally with hid-recorder from
>>>> https://gitlab.freedesktop.org/libevdev/hid-tools/
>>>
>>> Report descriptor is below:
>>>
>>> 05 0d 09 02 a1 01 85 01 09 22 a1 02 09 42 15 00 25 01 75 01 95 01 81 02
>>> 09 32 81 02 95 06 81 03 75 08 09 51 95 01 81 02 05 01 26 ff 0f 75 10 55
>>> 0e 65 33 09 30 35 00 46 b5 04 81 02 46 8a 03 09 31 81 02 c0 05 0d 09 54
>>> 95 01 75 08 81 02 85 08 09 55 25 05 b1 02 c0 05 0c 09 01 a1 01 85 02 09
>>> e9 09 ea 0a ae 01 09 e2 09 30 15 01 25 0c 75 10 95 01 81 00 c0
>>>
>>> Events were collected using getevent call in adb shell in android:
>>>
>>> On 4.19
>>>
>>> # getevent -l
>>>
>>> add device 7: /dev/input/event6
>>> name: "BLE-M1 UNKNOWN"
>>>
>>> /dev/input/event6: EV_ABS ABS_MT_TRACKING_ID 00000000
>>> /dev/input/event6: EV_ABS ABS_MT_POSITION_X 00000800
>>> /dev/input/event6: EV_ABS ABS_MT_POSITION_Y 00000d60
>>> /dev/input/event6: EV_KEY BTN_TOUCH DOWN
>>> /dev/input/event6: EV_SYN SYN_REPORT 00000000
>>> /dev/input/event6: EV_ABS ABS_MT_TRACKING_ID ffffffff
>>> /dev/input/event6: EV_KEY BTN_TOUCH UP
>>> /dev/input/event6: EV_SYN SYN_REPORT 00000000
>>> /dev/input/event6: EV_ABS ABS_MT_TRACKING_ID 00000001
>>> /dev/input/event6: EV_KEY BTN_TOUCH DOWN
>>> /dev/input/event6: EV_SYN SYN_REPORT 00000000
>>> /dev/input/event6: EV_ABS ABS_MT_TRACKING_ID ffffffff
>>> /dev/input/event6: EV_KEY BTN_TOUCH UP
>>> /dev/input/event6: EV_SYN SYN_REPORT 00000000
>>>
>>> On 4.14
>>>
>>> add device 2: /dev/input/event5
>>> name: "BLE-M1 UNKNOWN"
>>>
>>> /dev/input/event5: EV_MSC MSC_SCAN 000d0042
>>> /dev/input/event5: EV_KEY BTN_TOUCH DOWN
>>> /dev/input/event5: EV_KEY BTN_DIGI DOWN
>>> /dev/input/event5: EV_ABS ABS_MISC 00000001
>>> /dev/input/event5: EV_ABS ABS_X 00000800
>>> /dev/input/event5: EV_ABS ABS_Y 00000d60
>>> /dev/input/event5: EV_ABS 0029 00000001
>>> /dev/input/event5: EV_SYN SYN_REPORT 00000000
>>>
>>> /dev/input/event5: EV_MSC MSC_SCAN 000d0042
>>> /dev/input/event5: EV_KEY BTN_TOUCH UP
>>> /dev/input/event5: EV_KEY BTN_DIGI UP
>>> /dev/input/event5: EV_ABS 0029 00000000
>>> /dev/input/event5: EV_SYN SYN_REPORT 00000000
>>>
>>> /dev/input/event5: EV_MSC MSC_SCAN 000d0042
>>> /dev/input/event5: EV_KEY BTN_TOUCH DOWN
>>> /dev/input/event5: EV_KEY BTN_DIGI DOWN
>>> /dev/input/event5: EV_ABS 0029 00000001
>>> /dev/input/event5: EV_SYN SYN_REPORT 00000000
>>>
>>> /dev/input/event5: EV_MSC MSC_SCAN 000d0042
>>> /dev/input/event5: EV_KEY BTN_TOUCH UP
>>> /dev/input/event5: EV_KEY BTN_DIGI UP
>>> /dev/input/event5: EV_ABS 0029 00000000
>>> /dev/input/event5: EV_SYN SYN_REPORT 00000000
>>>
>>>
>>> As I have little understanding of the framework, use cases and of the
>>> flow, I am sorry, if the information provided above is
>>>
>>> incomplete (w.r.t. what you were expecting).
>>>
>>>
>>> Thanks
>>>
>>> Neeraj
>>>
>>>> Cheers,
>>>> Benjamin
>>>>
>>>>>
>>>>> Thanks
>>>>> Neeraj
>>>>>
>>>>> --
>>>>> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
>>>>> member of the Code Aurora Forum, hosted by The Linux Foundation
>>>>>
>>
>> --
>> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
>> member of the Code Aurora Forum, hosted by The Linux Foundation
>>
>

--
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
member of the Code Aurora Forum, hosted by The Linux Foundation

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