Return-Path: Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 10.3 \(3273\)) Subject: Re: [PATCH v2] gatt-server: Implement NegotiatedMTU property on Device1 From: Jonah Petri In-Reply-To: Date: Wed, 6 Sep 2017 11:44:31 -0400 Cc: Emil Lenngren , Bluez mailing list Message-Id: <1AE5314A-1E01-43B7-AFA3-4D82DA9ED755@sense.com> References: <9B25967D-16B8-4335-BE03-8FFD02D400FB@sense.com> <5234EF82-463D-4521-ABDB-C68132933BD7@sense.com> To: Luiz Augusto von Dentz Sender: linux-bluetooth-owner@vger.kernel.org List-ID: Hello Luiz, Thanks for looking at my proposal. > On Sep 6, 2017, at 10:14 AM, Luiz Augusto von Dentz = wrote: >=20 > Your implementation is not really LE specific, in fact it will cause > the clients to believe they connected over LE if the MTU appears, > besides with cross transport pairing and dual mode topology this has > to work either way or then we have to disable GATT completely on > BR/EDR. Of course, yes, my previous implementation is not appropriate for this = new API. There's differences of opinion about what the API should be, = and I'm proposing a revised API to address feedback from yourself and = others. If there's consensus that my revised API is appropriate, I'll = then propose an implementation. >=20 > Also, the AcquireWrite and AcquireNotify should fulfil most of the use > cases where GATT is used just as transport to another protocol, is > that what you are intending to do? I'm merely conforming to an existing protocol, which requires me to only = publish GATT attributes which are length <=3D MTU - 3. This is because = we can't depend on Long Read and Long Write support from BTLE clients. = In cases where a larger MTU has been negotiated, I need to take = advantage of it, for optimal throughput. I didn't design the protocol, but it's out there in the wild, and I need = to support it. >=20 > Having an API just for a very specific use case that in the future may > actually disappear with OSes adopting L2CAP CoC is not very nice. We already have several LE-specific APIs (e.g. LEAdvertisingManager), so = I don't understand this objection. BTLE GATT will be with us = essentially forever. Also, I've proposed marking this dbus property as = experimental, so I don't see the problem with trying it out. It = addresses a real need. Best, Jonah=