[pulseaudio-discuss] [RFCv2 13/17] bluetooth: Only call *Acquire() if using BlueZ' Media API

[João Paulo Rechi Vita]

On Thu, Apr 18, 2013 at 10:43 AM, Mikel Astiz <mikel.astiz.oss at gmail.com> wrote:
> Hi João Paulo,
>
> On Mon, Apr 15, 2013 at 11:53 PM,  <jprvita at gmail.com> wrote:
>> From: João Paulo Rechi Vita <jprvita at openbossa.org>
>>
>> When the transport backend is oFono the stream file descriptor is passed
>> through the NewConnection() method call. Additionally, set the kernel
>> default SCO MTU value for block size (since this information is not
>> available) and the transport codec, which also comes in the
>> NewConnection() method call.
>> ---
>>  src/modules/bluetooth/bluetooth-util.c | 20 ++++++++++++++++++++
>>  1 file changed, 20 insertions(+)
>>
>> diff --git a/src/modules/bluetooth/bluetooth-util.c b/src/modules/bluetooth/bluetooth-util.c
>> index ae98029..d72137b 100644
>> --- a/src/modules/bluetooth/bluetooth-util.c
>> +++ b/src/modules/bluetooth/bluetooth-util.c
>> @@ -1854,6 +1854,26 @@ int pa_bluetooth_transport_acquire(pa_bluetooth_transport *t, bool optional, siz
>>      } else {
>>          pa_assert(t->device->discovery->version == BLUEZ_VERSION_5);
>>
>> +        if (t->profile == PROFILE_HFGW) {
>> +            struct handsfree_card *hf_card = pa_hashmap_get(t->device->discovery->hf_cards, t->path);
>> +
>> +            /* The correct block size should take into account the SCO MTU from
>> +             * the Bluetooth adapter and (for adapters in the USB bus) the MxPS
>> +             * value from the Isoc USB endpoint in use by btusb and should be
>> +             * made available to userspace by the Bluetooth kernel subsystem.
>> +             * The empiric value will be used meanwhile. */
>
> Why not take the MTU from the socket options?

The MTU informed through the SCO socket option informs the adapter
MTU, it doesn't take the USB endpoint MxPS into consideration. So if
we use that value the USB endpoint gets flooded (I imagine) and resets
the Bluetooth adapter. Vinicius is investigating this issue, but
hardcoding this value to 48 is the best we can do so far :(

>
>> +            if (imtu)
>> +                *imtu = 48;
>> +            if (omtu)
>> +                *omtu = 48;
>> +
>> +            if (hf_card) {
>> +                t->codec = hf_card->codec;
>> +                return hf_card->fd;
>
> As already mentioned before, this is not enough. You're handling the
> optional case only, while PA also relies on triggering an SCO
> connection actively and blocking until we get the fd.
>

Yes, I left this use case to be handled later on and I'm working on it
right now, to see what we can do. How are you doing to trigger this?
I'm trying with module-sine, setting the bluetooth sink as the
fallback one, but this doesn't seem to trigger a sink resume.

> Considering this seems quite tricky with the current oFono API, I'd
> suggest it gets changed for the convenience of PA and other similar
> clients. Perhaps I'm missing some D-Bus magic to achieve this though.
>
>> +            } else
>> +                return -1;
>> +        }
>> +
>>          method = optional ? "TryAcquire" : "Acquire";
>>          pa_assert_se(m = dbus_message_new_method_call(t->owner, t->path, "org.bluez.MediaTransport1", method));
>>      }
>> --
>
> Cheers,
> Mikel
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