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From:   Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Date:   Fri, 10 Jul 2020 13:27:05 -0700
Message-ID: <CABBYNZJ2ak66EK42owiLtk1Gqu-RMoXUHu8a1eQVVNQ+syh5cw@mail.gmail.com>
Subject: Re: Temporary device removal during discovery
To:     Bastien Nocera <hadess@hadess.net>
Cc:     Andrey Batyiev <batyiev@gmail.com>,
        linux-bluetooth <linux-bluetooth@vger.kernel.org>
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Hi Bastien,

On Fri, Jul 10, 2020 at 12:00 PM Bastien Nocera <hadess@hadess.net> wrote:
>
> On Fri, 2020-07-10 at 11:06 -0700, Luiz Augusto von Dentz wrote:
> > Hi Bastien,
> >
> > On Thu, Jul 9, 2020 at 1:26 AM Bastien Nocera <hadess@hadess.net>
> > wrote:
> > > On Thu, 2020-07-09 at 01:57 +0300, Andrey Batyiev wrote:
> > > > Hi Luiz,
> > > >
> > > > On Thu, Jul 9, 2020 at 12:14 AM Luiz Augusto von Dentz
> > > > <luiz.dentz@gmail.com> wrote:
> > > > > The delta logic might be a nice addition as a separate patch,
> > > > > it is
> > > > > more for detecting devices disappearing then actually cleanup
> > > > > during
> > > > > power off.
> > > > No-no, it's not about adapter powering off.
> > > >
> > > > I meant that (external) devices never disappear from the bluez
> > > > device
> > > > list during the discovery,
> > > > even if the (external) devices are turned off (i.e. they should
> > > > be
> > > > purged by bluez).
> > > >
> > > > So:
> > > > - bluez is central
> > > > - bluez is discovering
> > > > - peripheral appear for a moment, than disappear (i.e. peripheral
> > > > would be turned off)
> > > > - bluez would not remove device from the list (at least until
> > > > discovery is stopped)
> > > >
> > > > Use case:
> > > > - bluez is monitoring environment (discovering literally forever)
> > > > - peripherals are brought in and out of bluez visibility range
> > > > - bluez list of visible devices grows infinitely and causes
> > > > problems
> > > > (hundreds of devices)
> > >
> > > I'd also expect devices that are recently discovered to disappear
> > > if
> > > they haven't replied to a discovery in 30 seconds. It would stop
> > > GNOME's Bluetooth Settings's Bluetooth list forever expanding.
> > >
> > > Or we need to give the ability for front-ends to do that by
> > > exporting
> > > the "last seen" dates.
> >
> > I am fine with that as well, 30 seconds doesn't sound too bad even
> > for
> > cleanup temporary devices as the current 3 minutes seems awful long
> > sometimes, we could perhaps have a filter for configuring that though
> > so if the application wants to have its own timeout, the only problem
> > is if there are multiple application doing that on parallel we would
> > need a strategy on how to handle that.
>
> In which case it might be easier to export that last seen date,
> otherwise that's just a lot of moving parts inside bluetoothd when we
> could filter it trivially in the front-ends.
>
Right, we still need to clean up the temporary devices though, but
perhaps adding a LastSeen property is not a bad idea after all so
applications can do this sort of filtering themselves.

-- 
Luiz Augusto von Dentz