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From:   Alain Michaud <alainmichaud@google.com>
Date:   Fri, 1 May 2020 13:40:39 -0400
Message-ID: <CALWDO_XG7PG8KCy0rraZZm0L12baSyWzxfCJnUkNBJX=APhQ_A@mail.gmail.com>
Subject: Re: [BlueZ PATCH v1] shared/gatt-client:Ignore orphaned characteristics
To:     Marcel Holtmann <marcel@holtmann.org>
Cc:     Alain Michaud <alainm@chromium.org>,
        BlueZ <linux-bluetooth@vger.kernel.org>
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On Fri, May 1, 2020 at 1:32 PM Marcel Holtmann <marcel@holtmann.org> wrote:
>
> Hi Alain,
>
> >>> The gatt discovery proceedure simplification to discover all
> >>> characteristics at once has exposed a device side issue where some
> >>> device implementation reports orphaned characteristics.  While this
> >>> technically shouldn't be allowed, some instances of this were observed
> >>> (namely on some Android phones).
> >>>
> >>> The fix is to simply skip over orphaned characteristics and continue
> >>> with everything else that is valid.
> >>>
> >>> This has been tested as part of the Android CTS tests against an
> >>> affected platform and was confirmed to have worked around the issue.
> >>> ---
> >>>
> >>> src/shared/gatt-client.c | 5 ++++-
> >>> 1 file changed, 4 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/src/shared/gatt-client.c b/src/shared/gatt-client.c
> >>> index 963ad619f..d604c77a3 100644
> >>> --- a/src/shared/gatt-client.c
> >>> +++ b/src/shared/gatt-client.c
> >>> @@ -632,7 +632,10 @@ static bool discover_descs(struct discovery_op *op, bool *discovering)
> >>>                      util_debug(client->debug_callback, client->debug_data,
> >>>                              "Failed to insert characteristic at 0x%04x",
> >>>                              chrc_data->value_handle);
> >>> -                     goto failed;
> >>> +
> >>> +                     /* Skip over invalid characteristic */
> >>> +                     free(chrc_data);
> >>> +                     continue;
> >>>              }
> >>
> >> should we add a warning here?
> > Is there a good way other than the util_debug mechanism to write  a warning?
>
> you could just use btd_warn() here. If this gets too noisy, we either remove it later or we introduce a btd_warn_ratelimited() or btd_warn_once().
This being under src/shared, I wasn't sure if that was acceptable to
add a btd dependency here, especially with the work to avoid it via
the util_debug.  Happy to do either way, just want to make sure the
guidance is clear.

>
> Regards
>
> Marcel
>