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Subject: Re: [BlueZ PATCH v1] shared/gatt-client:Ignore orphaned
 characteristics
From:   Marcel Holtmann <marcel@holtmann.org>
In-Reply-To: <CALWDO_XG7PG8KCy0rraZZm0L12baSyWzxfCJnUkNBJX=APhQ_A@mail.gmail.com>
Date:   Fri, 1 May 2020 20:00:54 +0200
Cc:     Alain Michaud <alainm@chromium.org>,
        BlueZ <linux-bluetooth@vger.kernel.org>
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References: <20200501144037.1684-1-alainm@chromium.org>
 <4195BFB9-1586-435F-8FC2-ED215959A591@holtmann.org>
 <CALWDO_W4AquYjw5LZR+pbFnPEB=shYKDH7_JDGHexpsXUnC7aA@mail.gmail.com>
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 <CALWDO_XG7PG8KCy0rraZZm0L12baSyWzxfCJnUkNBJX=APhQ_A@mail.gmail.com>
To:     Alain Michaud <alainmichaud@google.com>
Sender: linux-bluetooth-owner@vger.kernel.org
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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.

good point. My bad. You better leave the logging out then.

Regards

Marcel