Re: [PATCH v2 10/12] HID: input: remove the need for HID_QUIRK_INVERT

[Ping Cheng <pinglinux@gmail.com>]

Sorry for the noise. Hit the wrong buttons...

On Wed, Feb 9, 2022 at 9:21 PM Ping Cheng <pinglinux@gmail.com> wrote:
>
> On Thu, Feb 3, 2022 at 6:33 AM Benjamin Tissoires
> <benjamin.tissoires@redhat.com> wrote:
> >
> > HID_QUIRK_INVERT is kind of complex to deal with and was bogus.
> >
> > Furthermore, it didn't make sense to use a global per struct hid_device
> > quirk for something dynamic as the current state.
> >
> > Store the current tool information in the report itself, and re-order
> > the processing of the fields to enforce having all the tablet "state"
> > fields before getting to In Range and other input fields.
> >
> > This way, we now have all the information whether a tool is present
> > or not while processing In Range.
> >
> > This new behavior enforces that only one tool gets forwarded to userspace
> > at the same time, and that if either eraser or invert is set, we enforce
> > BTN_TOOL_RUBBER.
> >
> > Note that the release of the previous tool now happens in its own EV_SYN
> > report so userspace doesn't get confused by having 2 tools.
> >
> > These changes are tested in the following hid-tools regression tests:
> > https://gitlab.freedesktop.org/libevdev/hid-tools/-/merge_requests/127
> >
> > Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
> >
> > ---
> >
> > Changes in v2:
> > - rework the entire tool switching, this makes the processing
> >   slightly more complex but is better for existing userspace.
> > ---
> >  drivers/hid/hid-input.c | 98 +++++++++++++++++++++++++++++++++++++----
> >  include/linux/hid.h     |  6 ++-
> >  2 files changed, 95 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
> > index 61d91117f4ae..9f8853640648 100644
> > --- a/drivers/hid/hid-input.c
> > +++ b/drivers/hid/hid-input.c
> > @@ -63,8 +63,11 @@ static const struct {
> >   * This still leaves us 65535 individual priority values.
> >   */
> >  static const __u32 hidinput_usages_priorities[] = {
> > +       HID_DG_ERASER,          /* Eraser (eraser touching) must always come before tipswitch */
> >         HID_DG_INVERT,          /* Invert must always come before In Range */
> > -       HID_DG_INRANGE,
> > +       HID_DG_TIPSWITCH,       /* Is the tip of the tool touching? */
> > +       HID_DG_TIPPRESSURE,     /* Tip Pressure might emulate tip switch */
> > +       HID_DG_INRANGE,         /* In Range needs to come after the other tool states */
> >  };
> >
> >  #define map_abs(c)     hid_map_usage(hidinput, usage, &bit, &max, EV_ABS, (c))
> > @@ -1365,9 +1368,38 @@ static void hidinput_handle_scroll(struct hid_usage *usage,
> >         input_event(input, EV_REL, usage->code, hi_res);
> >  }
> >
> > +static void hid_report_release_tool(struct hid_report *report, struct input_dev *input,
> > +                                   unsigned int tool)
> > +{
> > +       /* if the given tool is not currently reported, ignore */
> > +       if (!test_bit(tool, input->key))
> > +               return;
> > +
> > +       /*
> > +        * if the given tool was previously set, release it,
> > +        * release any TOUCH and send an EV_SYN
> > +        */
> > +       input_event(input, EV_KEY, BTN_TOUCH, 0);
> > +       input_event(input, EV_KEY, tool, 0);

Took a while for me to find the right device and setup the proper
system for the testing. This block missing the serial number:

        input_event(input, EV_MSC, MSC_SERIAL, 0);

Without this line, the next tool will not get its serial number.

> > +       input_event(input, EV_SYN, SYN_REPORT, 0);
> > +
> > +       report->tool = 0;
> > +}
> > +
> > +static void hid_report_set_tool(struct hid_report *report, struct input_dev *input,
> > +                               unsigned int new_tool)
> > +{
> > +       if (report->tool != new_tool)
> > +               hid_report_release_tool(report, input, report->tool);
> > +
> > +       input_event(input, EV_KEY, new_tool, 1);
> > +       report->tool = new_tool;
> > +}
> > +
> >  void hidinput_hid_event(struct hid_device *hid, struct hid_field *field, struct hid_usage *usage, __s32 value)
> >  {
> >         struct input_dev *input;
> > +       struct hid_report *report = field->report;
> >         unsigned *quirks = &hid->quirks;
> >
> >         if (!usage->type)
> > @@ -1418,25 +1450,75 @@ void hidinput_hid_event(struct hid_device *hid, struct hid_field *field, struct
> >         }
> >
> >         switch (usage->hid) {
> > +       case HID_DG_ERASER:
> > +               report->tool_active |= !!value;
> > +
> > +               /*
> > +                * if eraser is set, we must enforce BTN_TOOL_RUBBER
> > +                * to accommodate for devices not following the spec.
> > +                */
> > +               if (value)
> > +                       hid_report_set_tool(report, input, BTN_TOOL_RUBBER);
> > +               else if (report->tool != BTN_TOOL_RUBBER)
> > +                       /* value is off, tool is not rubber, ignore */
> > +                       return;
> > +
> > +               /* let hid-input set BTN_TOUCH */
> > +               break;
> > +
> >         case HID_DG_INVERT:
> > -               *quirks = value ? (*quirks | HID_QUIRK_INVERT) : (*quirks & ~HID_QUIRK_INVERT);
> > +               report->tool_active |= !!value;
> > +
> > +               /*
> > +                * If invert is set, we store BTN_TOOL_RUBBER.
> > +                */
> > +               if (value)
> > +                       hid_report_set_tool(report, input, BTN_TOOL_RUBBER);
> > +               else if (!report->tool_active)
> > +                       /* tool_active not set means Invert and Eraser are not set */
> > +                       hid_report_release_tool(report, input, BTN_TOOL_RUBBER);
> > +
> > +               /* no further processing */
> >                 return;
> >
> >         case HID_DG_INRANGE:
> > -               if (value) {
> > -                       input_event(input, usage->type, (*quirks & HID_QUIRK_INVERT) ? BTN_TOOL_RUBBER : usage->code, 1);
> > -                       return;
> > +               report->tool_active |= !!value;
> > +
> > +               if (report->tool_active) {
> > +                       /*
> > +                        * if tool is not set but is marked as active,
> > +                        * assume ours
> > +                        */
> > +                       if (!report->tool)
> > +                               hid_report_set_tool(report, input, usage->code);
> > +               } else {
> > +                       hid_report_release_tool(report, input, usage->code);
> >                 }
> > -               input_event(input, usage->type, usage->code, 0);
> > -               input_event(input, usage->type, BTN_TOOL_RUBBER, 0);
> > +
> > +               /* reset tool_active for the next event */
> > +               report->tool_active = false;
> > +
> > +               /* no further processing */
> >                 return;
> >
> > +       case HID_DG_TIPSWITCH:
> > +               report->tool_active |= !!value;
> > +
> > +               /* if tool is set to RUBBER we should ignore the current value */
> > +               if (report->tool == BTN_TOOL_RUBBER)
> > +                       return;

This case should return before HID_DG_INVERT is checked since we may
get TIPSWITCH bit before INVERT. In fact, the device that I tested
sends the tipswatch bit before the invert bit. So, I alway get a PEN
in and out before I get ERASER events, when I bring the pen in with
the side-switch/invert bit pressed.

However, we know not all devices support INVERT. We probably have to
keep the invert quirk to decide if BTN_TOOL_PEN should be set here or
wait until HID_DG_INVERT is reached.

If you are interested in the evtest output, please let me know. I'll
share it with you offline so we don't abuse this list...

Cheers,
Ping

> > +               break;
> > +
> >         case HID_DG_TIPPRESSURE:
> >                 if (*quirks & HID_QUIRK_NOTOUCH) {
> >                         int a = field->logical_minimum;
> >                         int b = field->logical_maximum;
> >
> > -                       input_event(input, EV_KEY, BTN_TOUCH, value > a + ((b - a) >> 3));
> > +                       if (value > a + ((b - a) >> 3)) {
> > +                               input_event(input, EV_KEY, BTN_TOUCH, 1);
> > +                               report->tool_active = true;
> > +                       }
> >                 }
> >                 break;
> >
> > diff --git a/include/linux/hid.h b/include/linux/hid.h
> > index eaad0655b05c..feb8df61168f 100644
> > --- a/include/linux/hid.h
> > +++ b/include/linux/hid.h
> > @@ -347,7 +347,7 @@ struct hid_item {
> >   */
> >  #define MAX_USBHID_BOOT_QUIRKS 4
> >
> > -#define HID_QUIRK_INVERT                       BIT(0)
> > +/* BIT(0) reserved for backward compatibility, was HID_QUIRK_INVERT */
> >  #define HID_QUIRK_NOTOUCH                      BIT(1)
> >  #define HID_QUIRK_IGNORE                       BIT(2)
> >  #define HID_QUIRK_NOGET                                BIT(3)
> > @@ -515,6 +515,10 @@ struct hid_report {
> >         unsigned maxfield;                              /* maximum valid field index */
> >         unsigned size;                                  /* size of the report (bits) */
> >         struct hid_device *device;                      /* associated device */
> > +
> > +       /* tool related state */
> > +       bool tool_active;                               /* whether the current tool is active */
> > +       unsigned int tool;                              /* BTN_TOOL_* */
> >  };
> >
> >  #define HID_MAX_IDS 256
> > --
> > 2.33.1
> >