Re: Trouble with an HP stylus

[Benjamin Tissoires <benjamin.tissoires@gmail.com>]

Hi Jiri, Eric,


On Tue, Jul 29, 2014 at 5:50 AM, Jiri Kosina <jkosina@suse.cz> wrote:
> On Thu, 24 Jul 2014, Éric Brunet wrote:
>
>> I have a HP EliteBook Revolve 810 (which is a hybrid laptop/tablet) with
>> the HP active pen that goes with it. I have installed fedora 20 (kernel
>> 3.15.6-200.fc20.x86_64) on this, and the pen does not work out of the box.
>> Playing with evtest, it appears that the kernel reports the X coordinate in
>> ABS_X and in ABS_Y, while the Y coordinate goes into ABS_Z and ABS_RX; here
>> are a few lines of output:
>>
>> Event: time 1406153996.865044, -------------- SYN_REPORT ------------
>> Event: time 1406153996.873047, type 3 (EV_ABS), code 0 (ABS_X), value 1087
>> Event: time 1406153996.873047, type 3 (EV_ABS), code 1 (ABS_Y), value 1087
>> Event: time 1406153996.873047, type 3 (EV_ABS), code 2 (ABS_Z), value 1599
>> Event: time 1406153996.873047, type 3 (EV_ABS), code 3 (ABS_RX), value 1599
>>
>> Of course, XOrg's evdev driver is confused and the pointer is stuck on the
>> diagonal X=Y.
>>
>> I guess this hardware needs a new quirk to usbhid, unless there is already
>> a way to correct it ?
>>
>> Here is the content of /sys/class/input/event8/device/uevent:
>>
>> PRODUCT=3/3eb/840b/111
>> NAME="Atmel Atmel maXTouch Digitizer Pen"
>> PHYS="usb-0000:00:1a.0-1.1/input0"
>> UNIQ=""
>> PROP=0
>> EV=1b
>> KEY=c01 1 0 0 0 0
>> ABS=100000f
>> MSC=10
>> MODALIAS=input:b0003v03EBp840Be0111-
>> e0,1,3,4,k100,140,14A,14B,ra0,1,2,3,18,m4,lsfw
>>
>> I hope I gave enough information on this. I don't read the mailing list,
>> please CC any answer.
>
> Does the patch below fix the problem for you please?
>

I have already seen this Atmel panel, and the problem was that they used twice X then twice Y to report coordinates:

0x05, 0x01,                    //     Usage Page (Generic Desktop)    590
0x55, 0x0e,                    //     Unit Exponent (-2)              592
0x65, 0x11,                    //     Unit (Centimeter,SILinear)      594
0x35, 0x00,                    //     Physical Minimum (0)            596
0x75, 0x10,                    //     Report Size (16)                598
0x95, 0x02,                    //     Report Count (2)                600
0x46, 0x00, 0x0a,              //     Physical Maximum (2560)         602
0x26, 0xff, 0x0f,              //     Logical Maximum (4095)          605
0x09, 0x30,                    //     Usage (X)                       608
0x81, 0x02,                    //     Input (Data,Var,Abs)            610
0x46, 0xa0, 0x05,              //     Physical Maximum (1440)         612
0x26, 0xff, 0x0f,              //     Logical Maximum (4095)          615
0x09, 0x31,                    //     Usage (Y)                       618
0x81, 0x02,                    //     Input (Data,Var,Abs)            620

I have no ideas why they did that, but this is a pretty bad idea. I thought at the time that it was just a prototype and that they would fix it for the release, but I was wrong.

I think, a better patch would simply consist in that:

diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
index 2619f7f..b70d4c3 100644
--- a/drivers/hid/hid-input.c
+++ b/drivers/hid/hid-input.c
@@ -603,7 +603,7 @@ static void hidinput_configure_usage(struct hid_input *hidinput, struct hid_fiel
                        if (field->flags & HID_MAIN_ITEM_RELATIVE)
                                map_rel(usage->hid & 0xf);
                        else
-                               map_abs(usage->hid & 0xf);
+                               map_abs_clear(usage->hid & 0xf);
                        break;
 
                case HID_GD_HATSWITCH:

-----

I have the report descriptors and some traces of it, so I could definitively make some more tests, but I will have to first finish the wacom bits I scheduled for today.

Eric, if you can give a shot to my patch (you can try Jiri's too, but I don't think it will work), that would simplify my process, and I will just have to reformat/submit it properly.

Cheers,
Benjamin
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