Re: [PATCH] HID: hid-input: occasionally report stylus battery even if not changed

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

M
On Wed, Oct 07, 2020 at 03:05:13PM -0700, Kenneth Albanowski wrote:
> I've tested this locally backported to a 4.19 variant; it does work,
> and provides the expected additional CHANGE events while safely
> limiting the rate.
> 
> This seems like a reasonable minimum improvement, just ensuring
> information already being pushed by HID reports can be utilized.
> 
> I'm unsure about mapping Digitizers.InRange to power_supply 'present',
> in the abstract. It seems there could be a device where
> Digitizers.BatteryStrength is sent, despite Digitizers.InRange=0, and
> the HID Usage Tables don't quite seem to rule this out (depending on
> how battery status collection interacts with 'the region where
> digitizing is possible', section 16.3.1.).
> 
> As-is, this is useful and sufficient to get more timely reports up to userspace.

Jiri, if there are no better ideas, maybe this one can be applied?

Thanks!

> 
> - Kenneth Albanowski
> 
> 
> On Wed, Sep 30, 2020 at 3:47 PM <dmitry.torokhov@gmail.com> wrote:
> >
> > There are styluses that only report their battery status when they are
> > touching the touchscreen; additionally we currently suppress battery
> > reports if capacity has not changed. To help userspace recognize how long
> > ago the device reported battery status, let's send the change event through
> > if either capacity has changed, or at least 30 seconds have passed since
> > last report we've let through.
> >
> > Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
> > ---
> >
> > This is a bit of RFC. Another option would be to mark the power supply
> > as either offline or not present when stylus leaves the surface instead
> > of saying it is online... Sebastian, any ideas/suggestions?
> >
> >  drivers/hid/hid-input.c | 5 ++++-
> >  include/linux/hid.h     | 1 +
> >  2 files changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
> > index 5da631d2ec9b..92b4c9bb6619 100644
> > --- a/drivers/hid/hid-input.c
> > +++ b/drivers/hid/hid-input.c
> > @@ -534,9 +534,12 @@ static void hidinput_update_battery(struct hid_device *dev, int value)
> >         capacity = hidinput_scale_battery_capacity(dev, value);
> >
> >         if (dev->battery_status != HID_BATTERY_REPORTED ||
> > -           capacity != dev->battery_capacity) {
> > +           capacity != dev->battery_capacity ||
> > +           ktime_after(ktime_get_coarse(), dev->battery_ratelimit_time)) {
> >                 dev->battery_capacity = capacity;
> >                 dev->battery_status = HID_BATTERY_REPORTED;
> > +               dev->battery_ratelimit_time =
> > +                       ktime_add_ms(ktime_get_coarse(), 30 * 1000);
> >                 power_supply_changed(dev->battery);
> >         }
> >  }
> > diff --git a/include/linux/hid.h b/include/linux/hid.h
> > index 875f71132b14..c76a18f88262 100644
> > --- a/include/linux/hid.h
> > +++ b/include/linux/hid.h
> > @@ -583,6 +583,7 @@ struct hid_device {                                                 /* device report descriptor */
> >         __s32 battery_report_id;
> >         enum hid_battery_status battery_status;
> >         bool battery_avoid_query;
> > +       ktime_t battery_ratelimit_time;
> >  #endif
> >
> >         unsigned long status;                                           /* see STAT flags above */
> > --
> > 2.28.0.709.gb0816b6eb0-goog
> >
> >
> > --
> > Dmitry

-- 
Dmitry