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Re: Should we expose all devices as if they were bonded?

From: Von Dentz, Luiz <luiz.von.dentz@intel.com>
Date: Thu, 17 Mar 2016 13:11:11 +0200
Message-ID: <CACumGOLfTDOk+zMZOtFK_dPrg26B3GBVh6ogDkcC+hRE-g+pPg@mail.gmail.com>
To: Rob Moran <Rob.Moran@arm.com>
Cc: "Christiansen, Kenneth R" <kenneth.r.christiansen@intel.com>, Jeffrey Yasskin <jyasskin@google.com>, public-web-bluetooth <public-web-bluetooth@w3.org>
Hi Rob,

There are device that advertise, notify one value and disconnect,
which creates a race condition where the application/page may not be
quick enough to catch the value which is then lost as the device
disconnects immediately to save power.

On Thu, Mar 17, 2016 at 1:06 PM, Rob Moran <Rob.Moran@arm.com> wrote:
> IMO having the device appear unbonded and requiring a user to re-discover services and re-register for events, etc. after a disconnect is a cleaner and more atomic approach.
> Requiring the user to register for service changed events and possibly holding stale services (as they may not exist after a reconnect) could create more edge cases and potential errors to cover.
> In this scenario, I think the item to persist between connections is the security context, so that any further reconnections don't require a user action to undertake, but still honour the original service / name filters.
> Cheers,
> Rob
> ________________________________________
> From: Christiansen, Kenneth R <kenneth.r.christiansen@intel.com>
> Sent: 17 March 2016 10:39
> To: Jeffrey Yasskin; public-web-bluetooth
> Subject: RE: Should we expose all devices as if they were bonded?
> At least for development purposes it would be nice to have them unbounded (but I guess we could have a way to change the behavior in devtools when it is open)
> I am not sure whether I want the notifications to be queued, at least not by default. Think about something like temperature change and heart rate measurements.
> Kenneth
>> -----Original Message-----
>> From: Jeffrey Yasskin [mailto:jyasskin@google.com]
>> Sent: Thursday, March 17, 2016 2:22 AM
>> To: public-web-bluetooth <public-web-bluetooth@w3.org>
>> Subject: Should we expose all devices as if they were bonded?
>> Two issues came up recently where the Bluetooth spec defines different
>> behavior depending on whether a device is bonded.
>> In https://groups.google.com/a/chromium.org/d/topic/web-
>> bluetooth/PQpZAFNlvT4/discussion
>> and https://github.com/thegecko/web-bluetooth-dfu/issues/12, Luiz is
>> suggesting that we have Web Bluetooth remember services, characteristics,
>> and descriptors across disconnection, even when there's no physical bond.
>> That's similar to treating the web site as bonded to the peripheral. We'd in
>> the case of no bond, we'd re-discover the known services, etc. after re-
>> connecting, and send service-changed events for the ones that have
>> changed. We'd also allow users to hold onto Service, etc. objects across
>> disconnect/connect pairs, and continue using the objects afterward. On the
>> other hand, if we treat pages as un-bonded, users would need to re-fetch
>> services, etc. before using them after a disconnect/reconnect pair.
>> In https://github.com/WebBluetoothCG/web-bluetooth/issues/220 and
>> https://bugs.chromium.org/p/chromium/issues/detail?id=589796, we have
>> to decide whether users need to re-subscribe to notifications after a
>> disconnection. If we treat pages as bonded, the notification state should
>> persist across disconnections. If we treat pages as non-bonded, the state
>> should reset to unsubscribed on disconnection. (3.G. If we keep the
>> page subscribed across disconnection, users might expect us to queue
>> notifications, or at least indications, and deliver them the next time the page
>> is connected. Should we do the same if the page is unloaded? That kind of
>> unbounded queueing seems problematic.
>> And, of course, beyond always treating a page as bonded or not-bonded, we
>> could make the page's bonded-ness depend on the presence of a physical
>> bond.
>> Are there other areas where treating the page as having or not-having a
>> bond would cause divergent behavior?
>> Which behavior do you folks think makes more sense for the web API?
>> Jeffrey
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Received on Thursday, 17 March 2016 11:11:41 UTC

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