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* Query regarding hid-multitouch.c driver in 4.14/4.19
@ 2019-11-13  2:29 Neeraj Upadhyay
  2019-11-13  9:30 ` Benjamin Tissoires
  0 siblings, 1 reply; 6+ messages in thread
From: Neeraj Upadhyay @ 2019-11-13  2:29 UTC (permalink / raw)
  To: jikos, benjamin.tissoires, rydberg
  Cc: linux-input, linux-kernel, linux-arm-msm-owner, prsood, gkohli

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?


Thanks
Neeraj

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


^ permalink raw reply	[flat|nested] 6+ messages in thread

end of thread, other threads:[~2019-12-09  3:51 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-11-13  2:29 Query regarding hid-multitouch.c driver in 4.14/4.19 Neeraj Upadhyay
2019-11-13  9:30 ` Benjamin Tissoires
2019-11-14  4:31   ` Neeraj Upadhyay
2019-11-22  4:41     ` Neeraj Upadhyay
     [not found]     ` <0101016e916ab42c-fbc61178-9bdd-42ba-b111-722c46db5dc1-000000@us-west-2.amazonses.com>
2019-11-22  9:25       ` Benjamin Tissoires
2019-12-09  3:51         ` Neeraj Upadhyay

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