linux-kernel - Re: [PATCH v2 2/3] HID: logitech-hidpp: Retry commands when device is busy

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Message-ID: <8b5b5954dac10226b243df931ff7ce75df1e21e6.camel@hadess.net>
Date:   Thu, 09 Feb 2023 16:50:27 +0100
From:   Bastien Nocera <hadess@...ess.net>
To:     Benjamin Tissoires <benjamin.tissoires@...hat.com>
Cc:     linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jiri Kosina <jikos@...nel.org>,
        "Peter F . Patel-Schneider" <pfpschneider@...il.com>,
        Filipe Laíns <lains@...eup.net>,
        Nestor Lopez Casado <nlopezcasad@...itech.com>
Subject: Re: [PATCH v2 2/3] HID: logitech-hidpp: Retry commands when device
 is busy

On Thu, 2023-02-09 at 15:50 +0100, Benjamin Tissoires wrote:
> On Feb 06 2023, Bastien Nocera wrote:
> > Handle the busy error coming from the device or receiver. The
> > documentation says a busy error can be returned when:
> > "
> > Device (or receiver) cannot answer immediately to this request
> > for any reason i.e:
> > - already processing a request from the same or another SW
> > - pipe full
> > "
> > 
> > Signed-off-by: Bastien Nocera <hadess@...ess.net>
> > ---
> > 
> > Same as v1
> > 
> >  drivers/hid/hid-logitech-hidpp.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> > 
> > diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-
> > logitech-hidpp.c
> > index 1952d8d3b6b2..9e94026de437 100644
> > --- a/drivers/hid/hid-logitech-hidpp.c
> > +++ b/drivers/hid/hid-logitech-hidpp.c
> > @@ -295,6 +295,7 @@ static int hidpp_send_message_sync(struct
> > hidpp_device *hidpp,
> >          */
> >         *response = *message;
> >  
> > +retry:
> >         ret = __hidpp_send_report(hidpp->hid_dev, message);
> >  
> >         if (ret) {
> > @@ -321,6 +322,10 @@ static int hidpp_send_message_sync(struct
> > hidpp_device *hidpp,
> >                         response->report_id ==
> > REPORT_ID_HIDPP_VERY_LONG) &&
> >                         response->fap.feature_index ==
> > HIDPP20_ERROR) {
> >                 ret = response->fap.params[1];
> > +               if (ret == HIDPP20_ERROR_BUSY) {
> > +                       dbg_hid("%s:got busy hidpp 2.0 error %02X,
> > retrying\n", __func__, ret);
> > +                       goto retry;
> 
> I must confess, I blocked a little bit there to decide whether or not
> using goto here was OK.
> 
> But then I reliazed that there is no way to leave that function if
> the
> device is buggy and constantly sends back ERROR_BUSY. So I am not
> very
> found of the idea of having that got after all.
> 
> Would you mind respinning that patch with a bounded loop for the
> retries
> instead of using a goto? I'd like the driver to give up after a few
> retries if the device is not fair.

Done in v3.