Re: [PATCH] Add HID's to hid-microsoft driver of Surface Type/TouchCover 2 to fix bug

From: Benjamin Tissoires
Date: Wed Jan 22 2014 - 10:07:20 EST

Hi Reyad,

On Wed, Jan 22, 2014 at 12:05 AM, Reyad Attiyat <reyad.attiyat@xxxxxxxxx> wrote:
> Hello Benjamin,
>>> Hi,
>>> Thanks for reminding me of hid_have_special_driver[]. I noticed that
>>> this device has the HID_DG_CONTACTID and in the comment of the
>>> hid_have_sepcial_driver[]
>>> * Please note that for multitouch devices (driven by hid-multitouch driver),
>>> * there is a proper autodetection and autoloading in place (based on presence
>>> * of HID_DG_CONTACTID), so those devices don't need to be added to this list,
>>> * as we are doing the right thing in hid_scan_usage().
>>> This device should not be driven by hid-multitouch as it does not
>>> handle keyboard/mouse input devices.
>>> I submitted a new patch below with it added. I believe it should still
>>> be part of this array, in case this kind of implementation is
>>> fixed/updated.
>> This implementation is perfectly fine (I am referring to the "fixed/updated"):
>> - if your device should be driven by hid-multitouch, then you _don't_
>> add it to hid_have_special_driver
>> - if your device should not be driven by hid-multitouch, then you
>> _need_ to add it to hid_have_special_driver.
>> Adding the device to hid_have_special_driver prevents the detection of
>> the group HID_GRP_MULTITOUCH, so you will not end with a race between
>> hid-multitouch and your special hid driver.
> Thanks for clearing that up. I understand the proper use of this array
> now, under this circumstance and am glad to know that there will be no
> race when added.
>>> From 291742873dcf181faf9657b41279487f31302c73 Mon Sep 17 00:00:00 2001
>>> From: Reyad Attiyat <reyad.attiyat@xxxxxxxxx>
>>> Date: Tue, 21 Jan 2014 01:22:25 -0600
>>> Subject: [PATCH 1/1] Added in HID's for Microsoft Surface Type/Touch cover 2.
>>> This is to fix bug 64811 where this device is detected as a multitouch device
>> You are missing a commit message here (the first message you sent
>> would fit perfectly here).
> Sorry about that, I'm new to submitting patches to these mailing lists.
>> Other than that, I played a little with the report descriptor pointed
>> in the bugzilla.
>> I think I will be able to handle this touch cover in hid-multitouch,
>> but that would require more testings/debugging. Microsoft seems to
>> have implemented an indirect (dual) touchpad here, but until we know
>> which mode we should put it into, it's going to be tricky to set it up
>> correctly.
>> One last thing, in the bugzilla, in the comment 2 you say: "I still
>> have issues with the type cover 2 even with this fix". Are you still
>> experiencing those disconnection? If so, maybe we should switch to
>> hid-multitouch at some point.
> I tried some patches that I think you posted to hid-input about hid-multitouch.
> The patches added in support for function callbacks to allow for a
> generic protocol.
> This worked after I changed mt_input_mapping() to set the protocol to
> mt_protocol_generic
> 851 * such as Mouse that might have the same GenericDesktop usages. */
> 852 if (field->application != HID_DG_TOUCHSCREEN &&
> 853 field->application != HID_DG_PEN &&
> 854 field->application != HID_DG_TOUCHPAD)
> 855 td->protocols[report_id] = mt_protocol_generic;

yep, I was referring to this patch series. Thanks for testing :)

> I still experience the disconnects with both of these solutions. Do
> you have any idea what could cause this?

Well, my first thought may be a mechanical issue (don't know if the
cover is still using magnets).
As for the software/firmware issue, I can think of two possibilities right now:
- the device expects us to empty its whole data queues, and we don't.
So after some time, it resets itself. I remember on the bug report of
having seen several USB devices, so maybe one of them is ignored and
it does not like it
- firmware issue: the device has been properly tested/certified in a
specific mode (the feature INPUT_MODE shows a maximal of 10,
multitouch devices generally have only 2 modes, not 10). So if we are
not in the same mode it is under Windows, then we are screwed.

> It seems to happen when I'm typing fast or holding a key. I'm guessing
> the only way to fix this properly is
> to snoop USB packets in Windows to see how the device is handled there.

Yep, that seems like a plan.

> Another bug is the device stays on, lit, in standby mode.

I would say that means that the suspend do not ask the usb keyboard to
go to sleep so that you can wake your device up by hitting a key (I
guess, I am not 100% sure regarding suspend and PM). Maybe play with
the suspend/resume callbacks and see if they are called.

> What do you think is the best solution to take? By that I mean should
> I keep the patch as part of hid-microsoft?

Yep. For the time being, keep it under hid-microsoft. If I manage to
convince myself to resubmit the patches I sent last month (which I
definitively should do), then we can think at switching it to
hid-multitouch if there is a gain (touchpad reporting full touches,
not mouse emulation, and/or fix the disconnect issue).

However, I don't plan to buy a surface 2 soon. I will not be able to
debug it easily, so you will be on your own :) Still, do not hesitate
to send me usb captures or hid-record[1] logs if you need a hand.


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