linux-kernel - Re: [PATCH 1/2] HID: input: map digitizer battery usage

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Date:   Tue, 1 Aug 2017 09:53:20 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Jiri Kosina <jikos@...nel.org>
Cc:     Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Jason Gerecke <killertofu@...il.com>,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] HID: input: map digitizer battery usage

On Tue, Aug 01, 2017 at 04:35:33PM +0200, Jiri Kosina wrote:
> On Mon, 31 Jul 2017, Dmitry Torokhov wrote:
> 
> > We already mapped battery strength reports from the generic device
> > control page, but we did not update capacity from input reports, nor we
> > mapped the battery strength report from the digitizer page, so let's
> > implement this now.
> > 
> > Batteries driven by the input reports will now start in "unknown" state,
> > and will get updated once we receive first report containing battery
> > strength from the device.
> > 
> > Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
> > ---
> >  drivers/hid/hid-input.c | 181 ++++++++++++++++++++++++++++++++----------------
> >  include/linux/hid.h     |   2 +
> >  2 files changed, 124 insertions(+), 59 deletions(-)
> > 
> > diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
> > index ccdff1ee1f0c..5bcd4e4afb54 100644
> > --- a/drivers/hid/hid-input.c
> > +++ b/drivers/hid/hid-input.c
> > @@ -340,13 +340,42 @@ static unsigned find_battery_quirk(struct hid_device *hdev)
> >  	return quirks;
> >  }
> >  
> > +static int hidinput_scale_battery_capacity(struct hid_device *dev,
> > +					   int value)
> > +{
> > +	if (dev->battery_min < dev->battery_max &&
> > +	    value >= dev->battery_min && value <= dev->battery_max)
> > +		value = ((value - dev->battery_min) * 100) /
> > +			(dev->battery_max - dev->battery_min);
> > +
> > +	return value;
> > +}
> > +
> > +static int hidinput_query_battery_capacity(struct hid_device *dev)
> > +{
> > +	u8 *buf;
> > +	int ret;
> > +
> > +	buf = kmalloc(2, GFP_KERNEL);
> > +	if (!buf)
> > +		return -ENOMEM;
> > +
> > +	ret = hid_hw_raw_request(dev, dev->battery_report_id, buf, 2,
> > +				 dev->battery_report_type, HID_REQ_GET_REPORT);
> > +	ret = (ret != 2) ? -ENODATA : buf[1];
> > +
> > +	kfree(buf);
> > +
> > +	return hidinput_scale_battery_capacity(dev, ret);
> 
> Is it intentional that you call hidinput_scale_battery_capacity() here 
> even in 'ret == -ENODATA' case?
> 
> It wouldn't actually break anything currently, as the 
> 
> 	value >= dev->battery_min
> 
> check in hidinput_scale_battery_capacity() would most likely ensure that 
> the value wouldn't get overwritten and then propagated back, but it's 
> confusing and error-prone wrt. any future changes.
> Or have I missed something?

No, you are totally right, I'll resent the series in a few.

Thanks.

-- 
Dmitry