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SubjectRe: [PATCH v2] Input: Fix the HID usage of DPAD input event generation.
Hi Chris,

On Mon, Nov 2, 2020 at 6:24 PM Chris Ye <linzhao.ye@gmail.com> wrote:
>
> Hi Benjamin,
>
> I've tried the hid-tool for testing on my linux machine and it
> works. However the issue comes from a game controller I don't posses in
> hand right now so I can't physically connect it and provide the log from
> hid-tool recording. I do have the raw HID descriptor and in Linux
> kernel the debug info is like below:
>
> # cat /d/hid/0005\:27F8\:0BBE.0001/rdesc
> 05 01 09 05 a1 01 a1 02 15 81 25 7f 05 01 09 01 a1 00 75 08 95 04 35 00
> 46 ff 00 09 30 09 31 09 32 09 35 81 02 75 08 95 02 15 01 26 ff 00 09 39
> 09 39 81 02 c0 05 07 19 4f 29 52 15 00 25 01 75 01 95 04 81 02 05 01 09
> 90 09 91 09 92 09 93 75 01 95 04 81 02 75 01 95 10 05 09 19 01 29 10 81
> 02 06 02 ff 09 01 a1 01 15 00 25 01 09 04 75 01 95 01 81 02 c0 05 0c 09
> 01 a1 01 15 00 25 01 0a 24 02 75 01 95 01 81 06 c0 75 01 95 06 81 03 15
> 00 25 ff 05 02 09 01 a1 00 75 08 95 02 35 00 45 ff 09 c4 09 c5 81 02 c0
> 06 00 ff 09 80 75 08 95 08 15 00 26 ff 00 b1 02 c0 c0

Thanks for the report descriptor. That allowed me to add the device to
the tests at https://gitlab.freedesktop.org/bentiss/hid-tools/-/commits/wip/gamevice

And also to realize that... "how is that thing supposed to be working????"

>
> INPUT[INPUT]
> Field(0)
> Physical(GenericDesktop.Pointer)
> Application(GenericDesktop.GamePad)
> Usage(4)
> GenericDesktop.X
> GenericDesktop.Y
> GenericDesktop.Z
> GenericDesktop.Rz
> Logical Minimum(-127)
> Logical Maximum(127)
> Physical Minimum(0)
> Physical Maximum(255)
> Report Size(8)
> Report Count(4)
> Report Offset(0)
> Flags( Variable Absolute )
> Field(1)
> Physical(GenericDesktop.Pointer)
> Application(GenericDesktop.GamePad)
> Usage(2)
> GenericDesktop.HatSwitch
> GenericDesktop.HatSwitch
> Logical Minimum(1)
> Logical Maximum(255)
> Physical Minimum(0)
> Physical Maximum(255)
> Report Size(8)
> Report Count(2)
> Report Offset(32)
> Flags( Variable Absolute )
> Field(2)
> Application(GenericDesktop.GamePad)
> Usage(4)
> Keyboard.004f
> Keyboard.0050
> Keyboard.0051
> Keyboard.0052
> Logical Minimum(0)
> Logical Maximum(1)
> Physical Minimum(0)
> Physical Maximum(255)
> Report Size(1)
> Report Count(4)
> Report Offset(48)
> Flags( Variable Absolute )
> Field(3)
> Application(GenericDesktop.GamePad)
> Usage(4)
> GenericDesktop.D-PadUp
> GenericDesktop.D-PadDown
> GenericDesktop.D-PadRight
> GenericDesktop.D-PadLeft
> Logical Minimum(0)
> Logical Maximum(1)
> Physical Minimum(0)
> Physical Maximum(255)
> Report Size(1)
> Report Count(4)
> Report Offset(52)
> Flags( Variable Absolute )
> Field(4)
> Application(GenericDesktop.GamePad)
> Usage(16)
> Button.0001
> Button.0002
> Button.0003
> Button.0004
> Button.0005
> Button.0006
> Button.0007
> Button.0008
> Button.0009
> Button.000a
> Button.000b
> Button.000c
> Button.000d
> Button.000e
> Button.000f
> Button.0010
> Logical Minimum(0)
> Logical Maximum(1)
> Physical Minimum(0)
> Physical Maximum(255)
> Report Size(1)
> Report Count(16)
> Report Offset(56)
> Flags( Variable Absolute )
> Field(5)
> Application(ff02.0001)
> Usage(1)
> ff02.0004
> Logical Minimum(0)
> Logical Maximum(1)
> Physical Minimum(0)
> Physical Maximum(255)
> Report Size(1)
> Report Count(1)
> Report Offset(72)
> Flags( Variable Absolute )
> Field(6)
> Application(Consumer.0001)
> Usage(1)
> Consumer.0224
> Logical Minimum(0)
> Logical Maximum(1)
> Physical Minimum(0)
> Physical Maximum(255)
> Report Size(1)
> Report Count(1)
> Report Offset(73)
> Flags( Variable Relative )
> Field(7)
> Physical(Simulation.0001)
> Application(GenericDesktop.GamePad)
> Usage(2)
> Simulation.00c4
> Simulation.00c5
> Logical Minimum(0)
> Logical Maximum(255)
> Physical Minimum(0)
> Physical Maximum(255)
> Report Size(8)
> Report Count(2)
> Report Offset(80)
> Flags( Variable Absolute )
> FEATURE[FEATURE]
> Field(0)
> Application(GenericDesktop.GamePad)
> Usage(8)
> ff00.0080
> ff00.0080
> ff00.0080
> ff00.0080
> ff00.0080
> ff00.0080
> ff00.0080
> ff00.0080
> Logical Minimum(0)
> Logical Maximum(255)
> Physical Minimum(0)
> Physical Maximum(255)
> Report Size(8)
> Report Count(8)
> Report Offset(0)
> Flags( Variable Absolute )
>
> GenericDesktop.X ---> Absolute.X
> GenericDesktop.Y ---> Absolute.Y
> GenericDesktop.Z ---> Absolute.Z
> GenericDesktop.Rz ---> Absolute.Rz
> GenericDesktop.HatSwitch ---> Absolute.Hat0X
> GenericDesktop.HatSwitch ---> Absolute.Hat0Y

It took me a while to realize that you were needing
https://patchwork.kernel.org/project/linux-input/patch/20201101193452.678628-1-lzye@google.com/
for that.

But the weird part is that Hat switch are usually used as a single
variable, with values being mapped to Hat0X and Hat0Y. So I still
haven't manage to understand how the hid-input driver would map the
axis to a regular one between 1 and 255...

> Keyboard.004f ---> Key.Right
> Keyboard.0050 ---> Key.Left
> Keyboard.0051 ---> Key.Down
> Keyboard.0052 ---> Key.Up
> GenericDesktop.D-PadUp ---> Absolute.Hat1X
> GenericDesktop.D-PadDown ---> Sync.Report
> GenericDesktop.D-PadRight ---> Sync.Report
> GenericDesktop.D-PadLeft ---> Sync.Report
> Button.0001 ---> Key.BtnA
> Button.0002 ---> Key.BtnB
> Button.0003 ---> Key.BtnC
> Button.0004 ---> Key.BtnX
> Button.0005 ---> Key.BtnY
> Button.0006 ---> Key.BtnZ
> Button.0007 ---> Key.BtnTL
> Button.0008 ---> Key.BtnTR
> Button.0009 ---> Key.BtnTL2
> Button.000a ---> Key.BtnTR2
> Button.000b ---> Key.BtnSelect
> Button.000c ---> Key.BtnStart
> Button.000d ---> Key.BtnMode
> Button.000e ---> Key.BtnThumbL
> Button.000f ---> Key.BtnThumbR
> Button.0010 ---> Key.?
> ff02.0004 ---> Key.Btn0
> Consumer.0224 ---> Key.Back
> Simulation.00c4 ---> Absolute.Gas
> Simulation.00c5 ---> Absolute.Brake
>
> So you can see the device has D-Up, D-Down,D-Right,D-Left usages, and
> D-up is mapped to Hat1X.

OK, now I am starting to understand the problem better.

>
> Also if you can send HID report from hid-tool, you will see there are
> always intail events on Hat1X/Hat1Y as the HatDir is 0, even no DPAD
> buttons pressed. When you send HID report with D-DPAD buttons with
> different state, it doesn't generate any axis events because the HatDir
> internally is still 0 regardless the report value of the 4 DPAD usages.

That's the part I am a little bit stuck. I can emulate events for X,Y,
buttons,... but I am not sure how the gamepad sends the events for the
Hat switch and the D-Pad together.

Again, before we merge anything, I'd like to have the proper tests
written for it, on top of
https://gitlab.freedesktop.org/bentiss/hid-tools/-/commits/wip/gamevice
so we can ensure there is no regression for it, and that we will not
regress on it later on.

Cheers,
Benjamin

>
>
> Thanks!
>
> Chris
>
>
> On 11/2/20 12:16 AM, Benjamin Tissoires wrote:
> > Hi Chris,
> >
> >
> > On Sun, Nov 1, 2020 at 8:35 PM Chris Ye <lzye@google.com> wrote:
> >> Generic Desktop DPAD usage is mapped by hid-input, that only the first
> >> DPAD usage maps to usage type EV_ABS and code of an axis. If HID
> >> descriptor has DPAD UP/DOWN/LEFT/RIGHT HID usages and each of usage size
> >> is 1 bit, then only the first one will generate input event, the rest of
> >> the HID usages will be assigned to hat direction only.
> >> The hid input event should check the HID report value and generate
> >> HID event for its hat direction.
> >>
> >> Test: Connect HID device with Generic Desktop DPAD usage and press the
> >> DPAD to generate input events.
> > Thanks for the patch, but I would rather have a proper tests added to
> > https://gitlab.freedesktop.org/libevdev/hid-tools
> >
> > We already have gamepads tests, and it would be very nice to have this
> > patch reflected as a test as well. This would also allow me to better
> > understand the problem. I am not sure I follow the whole logic of this
> > patch without seeing the 2 variants of report descriptors.
> >
> > Cheers,
> > Benjamin
> >
> >> Signed-off-by: Chris Ye <lzye@google.com>
> >> ---
> >> drivers/hid/hid-input.c | 16 ++++++++++++----
> >> 1 file changed, 12 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
> >> index 9770db624bfa..6c1007de3409 100644
> >> --- a/drivers/hid/hid-input.c
> >> +++ b/drivers/hid/hid-input.c
> >> @@ -1269,7 +1269,7 @@ void hidinput_hid_event(struct hid_device *hid, struct hid_field *field, struct
> >> struct input_dev *input;
> >> unsigned *quirks = &hid->quirks;
> >>
> >> - if (!usage->type)
> >> + if (!usage->type && !field->dpad)
> >> return;
> >>
> >> if (usage->type == EV_PWR) {
> >> @@ -1286,9 +1286,17 @@ void hidinput_hid_event(struct hid_device *hid, struct hid_field *field, struct
> >> int hat_dir = usage->hat_dir;
> >> if (!hat_dir)
> >> hat_dir = (value - usage->hat_min) * 8 / (usage->hat_max - usage->hat_min + 1) + 1;
> >> - if (hat_dir < 0 || hat_dir > 8) hat_dir = 0;
> >> - input_event(input, usage->type, usage->code , hid_hat_to_axis[hat_dir].x);
> >> - input_event(input, usage->type, usage->code + 1, hid_hat_to_axis[hat_dir].y);
> >> + if (hat_dir < 0 || hat_dir > 8 || value == 0)
> >> + hat_dir = 0;
> >> + if (field->dpad) {
> >> + input_event(input, EV_ABS, field->dpad, hid_hat_to_axis[hat_dir].x);
> >> + input_event(input, EV_ABS, field->dpad + 1, hid_hat_to_axis[hat_dir].y);
> >> + } else {
> >> + input_event(input, usage->type, usage->code,
> >> + hid_hat_to_axis[hat_dir].x);
> >> + input_event(input, usage->type, usage->code + 1,
> >> + hid_hat_to_axis[hat_dir].y);
> >> + }
> >> return;
> >> }
> >>
> >> --
> >> 2.29.1.341.ge80a0c044ae-goog
> >>
>

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