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From:   Sonny Sasaka <sonnysasaka@chromium.org>
Date:   Mon, 25 Jan 2021 11:36:31 -0800
Message-ID: <CAO271mkbktDGgZeO5Z4X33F_5yjg0w5WS3Uw6Xbpqdcs_zP8zA@mail.gmail.com>
Subject: Re: [PATCH BlueZ] input/hog: Fix double registering report value callbacks
To:     Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Cc:     "linux-bluetooth@vger.kernel.org" <linux-bluetooth@vger.kernel.org>
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Hi Luiz,

I have revised the patch to using the notifyid to detect double
registration. Please take a another look. Thanks!

On Mon, Jan 11, 2021 at 9:47 AM Luiz Augusto von Dentz
<luiz.dentz@gmail.com> wrote:
>
> Hi Sonny,
>
> On Sat, Jan 9, 2021 at 4:34 PM Sonny Sasaka <sonnysasaka@chromium.org> wrote:
> >
> > In commit 23b69ab3e484 ("input/hog: Cache the HID report map"), we
> > optimized HOG reconnection by registering report value callbacks early,
> > but there was a bug where we also re-register the same report value
> > callbacks after at CCC write callback. We should handle this case by
> > avoiding the second callback register if we know we have done it
> > earlier.
> >
> > ---
> >  profiles/input/hog-lib.c | 12 ++++++++++++
> >  1 file changed, 12 insertions(+)
> >
> > diff --git a/profiles/input/hog-lib.c b/profiles/input/hog-lib.c
> > index 1f132aa4c..089f42826 100644
> > --- a/profiles/input/hog-lib.c
> > +++ b/profiles/input/hog-lib.c
> > @@ -80,6 +80,7 @@ struct bt_hog {
> >         struct bt_uhid          *uhid;
> >         int                     uhid_fd;
> >         bool                    uhid_created;
> > +       bool                    report_value_cb_registered;
> >         gboolean                has_report_id;
> >         uint16_t                bcdhid;
> >         uint8_t                 bcountrycode;
> > @@ -336,6 +337,13 @@ static void report_ccc_written_cb(guint8 status, const guint8 *pdu,
> >                 return;
> >         }
> >
> > +       /* If we already had the report map cache, we must have registered UHID
> > +        * and the report value callbacks. In that case, don't re-register the
> > +        * report value callbacks here.
> > +        */
> > +       if (hog->report_value_cb_registered)
> > +               return;
> > +
>
> Can't we check the report->notifyid instead of introducing yet another
> flag that seems to have the same intent of tracking if the report has
> been subscribed? In fact it seem there is something odd related to how
> we handle the CCC here, we do read it on ccc_read_cb but we don't
> check if its value is already set. Pehaps something like the following
> would be more complete solution, though we should really look into
> convert hog-lib to use bt_gatt_client instead of keep using GAttrib:
>
> diff --git a/profiles/input/hog-lib.c b/profiles/input/hog-lib.c
> index 1f132aa4c..34a4d7c3b 100644
> --- a/profiles/input/hog-lib.c
> +++ b/profiles/input/hog-lib.c
> @@ -360,15 +360,30 @@ static void ccc_read_cb(guint8 status, const
> guint8 *pdu, guint16 len,
>  {
>         struct gatt_request *req = user_data;
>         struct report *report = req->user_data;
> +       uint16_t value;
>
>         destroy_gatt_req(req);
>
> -       if (status != 0) {
> +       if (status || !len) {
>                 error("Error reading CCC value: %s", att_ecode2str(status));
>                 return;
>         }
>
> -       write_ccc(report->hog, report->hog->attrib, report->ccc_handle, report);
> +       if (len == 1)
> +               value = *pdu;
> +       else
> +               value = get_le16(pdu);
> +
> +       if (!value) {
> +               write_ccc(report->hog, report->hog->attrib, report->ccc_handle,
> +                         report);
> +               return;
> +       }
> +
> +       report->notifyid = g_attrib_register(report->hog->attrib,
> +                                       ATT_OP_HANDLE_NOTIFY,
> +                                       report->value_handle,
> +                                       report_value_cb, report, NULL);
>  }