From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Fri, 29 Apr 2011 10:56:25 -0700
From: Johan Hedberg <johan.hedberg@gmail.com>
To: Claudio Takahasi <claudio.takahasi@openbossa.org>
Cc: Luiz Augusto von Dentz <luiz.dentz@gmail.com>,
	linux-bluetooth@vger.kernel.org
Subject: Re: [PATCH 2/2] Remove wrong checking for legacy devices
Message-ID: <20110429175625.GA29649@jh-x301>
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Hi Claudio,

On Fri, Apr 29, 2011, Claudio Takahasi wrote:
> > On Fri, Apr 29, 2011 at 1:34 AM, Claudio Takahasi
> > <claudio.takahasi@openbossa.org> wrote:
> >> Infer that the found device is a legacy device based on the presence
> >> of its name in the storage is wrong.
> >> ---
> >>  src/event.c |    2 --
> >>  1 files changed, 0 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/src/event.c b/src/event.c
> >> index 5373e33..b873000 100644
> >> --- a/src/event.c
> >> +++ b/src/event.c
> >> @@ -481,8 +481,6 @@ void btd_event_device_found(bdaddr_t *local, bdaddr_t *peer, uint32_t class,
> >>
> >>        if (data)
> >>                legacy = FALSE;
> >> -       else if (name == NULL)
> >> -               legacy = TRUE;
> >>        else if (read_remote_features(local, peer, NULL, features) == 0) {
> >>                if (features[0] & 0x01)
> >>                        legacy = FALSE;
> >> --
> >
> > That was some use of it, but I can't remember now, maybe some broken
> > stack which has feature bits broken or we do actually infer if we ever
> > connect to the device before trying to read its features from the
> > storage.
> >
> >
> > --
> > Luiz Augusto von Dentz
> > Computer Engineer
> >
> 
> I found the commit that introduced this code, but it is still not clear to me:
> 989c60c0b9c96edf1fbdf80356abf05bac336673

I think the logic has gone like this: we get the remote features as a
side effect of a successful remote name request, so by checking for the
name first we don't do an unnecessary file-system lookup.

> BTW: why this information needs to be exposed through the DeviceFound() signal?
> It is not used internally in the adapter.c source.

It's useful for pairing UIs. If a device is expected to produce legacy
pairing when calling CreatePairedDevice the UI can ask the user for the
PIN *before* calling CreatePairedDevice and thereby eliminate the risk of
user response timeout locally.

Johan