> On 8 Dec 2016, at 06:18, Marcel Holtmann <marcel@xxxxxxxxxxxx> wrote: > > Hi Don, > >>>> Recent discussions on the bluez mailing list revealed it was not easy >>>> to disable duplicate device filtering from the d-bus interface. >>>> >>>> As a result, if I wanted to monitor LE devices entering and leaving the >>>> adapters range (using RSSI data), it was difficult. >>>> >>>> This patchset is a dirty hack to make this work. The first patch enables >>>> it on the kernel side, while the other two patches enable it from the bluez >>>> side. >>>> >>>> I understand there are concerns about flooding the d-bus interface when >>>> enabling this. I tried to write a throttling mechanism using the mainloop >>>> as my timer, but soon realized you can only have 1 device RSSI event >>>> per loop, so that wasn't going to work. Open to suggestions if still a >>>> concern. >>>> >>>> Posted as an RFC just to generate discussion. I expect I missed a lot of >>>> little details here, but wanted to post my proof of concept to see if this >>>> is something to work with. >>>> >>>> This patchset includes both the kernel and bluez patches. I understand this is >>>> not recommended for normal practice. But I thought for an RFC, it is nice to >>>> keep things together for now. >>> >>> I would avoid adding a new MGMT command and instead disabled >>> duplicated filtering if RSSI filtering is set since anyway RSSI >>> filtering needs to disable duplicates in order to do any RSSI >>> filtering reliable. So this would mean that if the user wants to see >>> to get duplicate filtering it needs to set a RSSI which should rate >>> limit as we would use a threshold. >> >> Hi Luiz, >> >> Ok, fair enough. I then simplified it down to a small kernel patch that >> seems to work if I set an RSSI threshold with SetDiscoveryFilter. >> >> I only do this on an active_scan. Not sure if I should do it for the >> passive scans too? >> >> If this looks ok, I will resubmit properly. > > I am not sure this is the best idea. So right now the kernel restarts scanning to get new RSSI values when we have a quirk set that strict scan filtering is performed by the controller (strict means address only). > > That is for discovery. Something started by the user and something that does not last over long times. Discovery is using active scanning which takes way more TX/RX time on air than passive scanning. It is also known to be causing more problems then it solves when run constantly. The reason is that it will interrupt CONNECT_REQ since SCAN_REQ are more likely to win based on their shorter packet size. > > So the main question is if you are after a certain set of devices (based on their address) and want to monitor their RSSI or are you after any device and want to match based on advertising data? > > The first one could be dealt with by using the whitelist, the second one is nasty from a power consumption point of view. Any long term operation there would be causing major headaches. > > Keep in mind that besides the kernel waking up (and USB transport), you also end up waking userspace all the time to process the information and send out over D-Bus. Which means you might going to wakeup even more processes. Can I just leap in here, as this is extremely relevant to the project I am working on. Sometimes you need to step back from what the ‘average user’ needs, and consider whether should allow certain behaviours to be enabled, even if they are not the default. What is ‘nasty’ to you in the big picture, is perfectly normal for me in a dedicated use case. Our application transfers data between devices (and there could be well over a thousand within range at a single time) and the central system using purely the MSD in the advertisements. Our linux ‘gateway’ boxes need to have continuous reception of advertisements, and we don’t care about the power consumption or processing implications - that is their dedicated job. We are currently unable to migrate our code from some older gatttool derived code to the modern APIs because it simply isn’t possible to work in the manner we need. (Note that our gateways use multiple BLE dongles, with at least one dedicated to receiving beacons while the others are used to connect to devices for archived data retrieval.) Please give some consideration to the fact that not everybody is using bluetooth for simple end-user devices, and whilst these are clearly the dominant use case, being able to engage esoteric modes of operation allows those of us who need to to consciously engage them as necessary for bespoke scenarios/applications. BLE is not just a desktop/peripheral technology :) Hope you don’t mind the interjection… Regards Stu -- Stuart Northfield +44 (0) 1223 566728 (Direct), +44 (0) 1223 566727 (Fax) Metanate Limited. Registered in England No 4046086 at: Lincoln House, Station Court, Great Shelford, Cambridge CB22 5NE, UK www.metanate.com (Consultancy) www.schemus.com (Data synchronisation) This e-mail and all attachments it may contain is confidential and intended solely for the use of the individual to whom it is addressed. Any views or opinions presented are those of the author and do not necessarily represent those of Metanate Ltd. 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