linux-kernel - Re: [PATCH 1/2] HID: logitech-hidpp: bail out if wtp

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Date:	Wed, 17 Dec 2014 02:32:52 +0100
From:	Peter Wu <peter@...ensteyn.nl>
To:	Benjamin Tissoires <benjamin.tissoires@...hat.com>
Cc:	Jiri Kosina <jkosina@...e.cz>,
	Nestor Lopez Casado <nlopezcasad@...itech.com>,
	Peter Hutterer <peter.hutterer@...-t.net>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] HID: logitech-hidpp: bail out if wtp_connect fails

Sorry for the rapid mail, I forgot to mention something.

wtp_connect won't work on non-HID++ devices. What about moving it down,
between the generic routines (reading protocol and name) and
hidpp_allocate_input? Then the connected parameter can also be dropped.

Kind regards,
Peter

On Wednesday 17 December 2014 00:33:55 Peter Wu wrote:
> On Tuesday 16 December 2014 17:06:01 Benjamin Tissoires wrote:
> > If wtp_connect() fails, that means most of the time that the device has
> > been disconnected. Subsequent attempts to contact the device will fail
> > too, so it's simpler to bail out earlier.
> > 
> > Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>
> > ---
> >  drivers/hid/hid-logitech-hidpp.c | 15 +++++++++------
> >  1 file changed, 9 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c
> > index d008d71..c0fb5fe 100644
> > --- a/drivers/hid/hid-logitech-hidpp.c
> > +++ b/drivers/hid/hid-logitech-hidpp.c
> > @@ -914,24 +914,24 @@ static int wtp_allocate(struct hid_device *hdev, const struct hid_device_id *id)
> >  	return 0;
> >  };
> >  
> > -static void wtp_connect(struct hid_device *hdev, bool connected)
> > +static int wtp_connect(struct hid_device *hdev, bool connected)
> >  {
> >  	struct hidpp_device *hidpp = hid_get_drvdata(hdev);
> >  	struct wtp_data *wd = hidpp->private_data;
> >  	int ret;
> >  
> >  	if (!connected)
> > -		return;
> > +		return 0;
> 
> "0" is success, what about -1 or -ENODEV here to signal an error? The
> following line (in hidpp_connect_event) returns on !connected, but that
> is no reason to return 0 here.
> 
> ("No connection" sounds like an error condition to me as "[wtp_]connect"
> cannot do something meaningful.)
> 
> Whether or not you change the return value is up to you. This patch is
> Reviewed-by: Peter Wu <peter@...ensteyn.nl>
> 
> Kind regards,
> Peter
> 
> >  	if (!wd->x_size) {
> >  		ret = wtp_get_config(hidpp);
> >  		if (ret) {
> >  			hid_err(hdev, "Can not get wtp config: %d\n", ret);
> > -			return;
> > +			return ret;
> >  		}
> >  	}
> >  
> > -	hidpp_touchpad_set_raw_report_state(hidpp, wd->mt_feature_index,
> > +	return hidpp_touchpad_set_raw_report_state(hidpp, wd->mt_feature_index,
> >  			true, true);
> >  }
> >  
> > @@ -1115,8 +1115,11 @@ static void hidpp_connect_event(struct hidpp_device *hidpp)
> >  	struct input_dev *input;
> >  	char *name, *devm_name;
> >  
> > -	if (hidpp->quirks & HIDPP_QUIRK_CLASS_WTP)
> > -		wtp_connect(hdev, connected);
> > +	if (hidpp->quirks & HIDPP_QUIRK_CLASS_WTP) {
> > +		ret = wtp_connect(hdev, connected);
> > +		if (ret)
> > +			return;
> > +	}
> >  
> >  	if (!connected || hidpp->delayed_input)
> >  		return;
> > 

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