[pulseaudio-discuss] [PATCH 1/3] bluetooth: Add 'bluez.alias' property

[Tanu Kaskinen]

On Mon, 2013-04-29 at 11:49 -0300, João Paulo Rechi Vita wrote:
> On Mon, Apr 29, 2013 at 11:38 AM, Tanu Kaskinen <tanu.kaskinen at intel.com> wrote:
> > On Mon, 2013-04-29 at 16:20 +0200, Mikel Astiz wrote:
> >> On Mon, Apr 29, 2013 at 4:01 PM, Tanu Kaskinen <tanu.kaskinen at intel.com> wrote:
> >> > On Fri, 2013-04-26 at 12:30 -0300, jprvita at gmail.com wrote:
> >> >>  src/modules/bluetooth/module-bluetooth-device.c | 1 +
> >> >>  1 file changed, 1 insertion(+)
> >> >>
> >> >> diff --git a/src/modules/bluetooth/module-bluetooth-device.c b/src/modules/bluetooth/module-bluetooth-device.c
> >> >> index c877df2..8695c80 100644
> >> >> --- a/src/modules/bluetooth/module-bluetooth-device.c
> >> >> +++ b/src/modules/bluetooth/module-bluetooth-device.c
> >> >> @@ -2243,6 +2243,7 @@ static int add_card(struct userdata *u) {
> >> >>      pa_proplist_sets(data.proplist, "bluez.path", device->path);
> >> >>      pa_proplist_setf(data.proplist, "bluez.class", "0x%06x", (unsigned) device->class);
> >> >>      pa_proplist_sets(data.proplist, "bluez.name", device->name);
> >> >> +    pa_proplist_sets(data.proplist, "bluez.alias", device->alias);
> >> >
> >> > device->alias is not guaranteed to be non-NULL, so this code can crash.
> >> > If the Alias property is non-optional in Bluez, bluetooth-util should
> >> > ensure that it is indeed always set.
> >>
> >> BlueZ 4 API guarantees the property will be present, and therefore
> >> device->alias should always be set. The obvious exception is BlueZ
> >> misbehaving, but this condition might hold true for device->name as
> >> well, which we're not checking either.
> >>
> >> I don't think there's any other scenario where the alias could be NULL
> >> and the name be set outside bluetooth-util.
> >>
> >> So while your point is valid, I suggest we fix this in a later patch,
> >> in a similar way that the BlueZ 5 patchset does (set device_info_valid
> >> to -1 if any non-optional property is missing).
> >
> > Ah, so this is fixed at least for BlueZ 5. Will the same property
> > parsing code be used for BlueZ 4? If not, does somebody promise to write
> > the fix for BlueZ 4?
> >
> 
> Both in BlueZ 5 and BlueZ 4 the 'Alias' property is not optional, if
> it's not present it's a bug in BlueZ. I don't think we should protect
> ourselfs more than the usual asserts before dereferencing pointers.

Yes, but our policy is to use assertions only for guarding against bugs
in our own process. Assertions are not used for handling bugs in other
processes, such as bluetoothd.

> If
> the property is not set but everything else is fine the only thing
> that will be missing is a value for PA_PROP_DEVICE_DESCRIPTION.
> Depending on how PulseAudio deals with description-less devices we can
> either not care or set a default description. Setting the device_info
> to invalid makes the device unusable.

I'm not sure if you're saying that it's fine to call pa_proplist_sets()
with a NULL value? It's not fine, it will cause a crash (due to an
assertion in pa_proplist_sets()).

Making the device unusable is an acceptable (and IMHO the best) way of
handling BlueZ bugs. But if everybody else thinks that doing it for
BlueZ 4 is waste of time, I won't insist on doing it.

-- 
Tanu

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