hcid and bluetoothd
Hi Marcel,
You said in an old e-mail that hcid is your playground for D-Bus services. Probably, hcid D-Bus should be the starting point for bluetoothd.
I would like to align your ideas to avoid future reworks.
D-Bus provides 4 types of messages:
1. Method call
2. Method reply
3. Signals
4. Error
Currently, only signals are sent. The following signals are sent as result of the hci commands:
- InquiryStart
- InquiryResult
- InquiryComplete
- RemoteName
path: /org/bluez/DevAgent
interface: org.bluez.DevAgent
The topics that I want discuss are:
1. hcid signals
In my opinion it is not necessary send signals to notity inquiry start/complete. Only signals for news devices are enough. Another aspect is, inquiry result can contain repeated devices. This approach could cause D-Bus app client overhead(inconsistency), by other hand if periodic inquiry is active repeated signals must be sent because more than one client can be filtering these signals and they can start at different time. :)
2. hcid and bluetoothd object path
What is the object path that you want use?
I suggested in an old email use a hierarchical paths. bluetoothd can be the main object path provided at /org/bluez/bluetoothd, hci D-Bus services could be provided at /org/bluez/bluetoothd/hci
3. D-Bus services
hci D-BUS services is the next step, I am going to starting coding ASAP. Regarding inquiry requests, what kind of implementation do you prefer, send method reply message or send only signals(like the current)?
If you use signals, all D-Bus client capturing D-Bus hci signals are able to see the new devices found. Using a method reply only the peer (requestor) will receive. Using a method reply approach, we can implement device class filters and avoid repeated devices. We have the same problem for remote name, disconnect, authentication/security, info, role switch and display connections.
4. bluetoothd
There are shared codes like(pand/bnep.c, pand/sdp.c, hidd/sdp.c, ...) that we need be aware.
It is NOT clear for me how hcid and bluetoothd should work. hcid must be running all the time, but the hci D-Bus service will be running only if the system has a D-Bus system daemon running. Therefore, who should register the hci object path? IMHO, bluetoothd should centralize all D-Bus services. It will not be easy separate the "normal" code from the "D-Bus code". Maybe your "new interface" that your are defining can solve this problem.
5. new interface
You said that a new interface for kernel and the userspace communication is being defined. What is the current status?
Regards,
Claudio.
Marcel Holtmann
maintainerHi Claudio,
Quoted 3 lines
You said in an old e-mail that hcid is your playground for D-Bus services. Probably, hcid D-Bus should be the starting point for bluetoothd.
since it is there and used, I think it is a good idea. At the moment it is optional and so we can test it. At some point I will make bluez-utils depend on D-Bus.
Quoted 16 lines
I would like to align your ideas to avoid future reworks.
D-Bus provides 4 types of messages:
1. Method call
2. Method reply
3. Signals
4. Error
Currently, only signals are sent. The following signals are sent as result of the hci commands:
- InquiryStart
- InquiryResult
- InquiryComplete
- RemoteName
path: /org/bluez/DevAgent
interface: org.bluez.DevAgent
Quoted 4 lines
The topics that I want discuss are:
1. hcid signals
In my opinion it is not necessary send signals to notity inquiry start/complete. Only signals for news devices are enough.
The idea behind also sending the InquiryStart and InquiryComplete events is that applications can show some graphical indications that the local device is now scanning for new devices in range. Since people can still call "hcitool scan" it is need for applications to know when someone else starts an inquiry.
Quoted 5 lines
Another aspect is, inquiry result can contain repeated devices. This approach could cause D-Bus app client overhead(inconsistency), by other hand if periodic inquiry is active repeated signals must be sent because more than one client can be filtering these signals and they can start at different time. :)
And the RSSI values may changes in the repeated reponses. The clients must do the filtering. There is no other way.
Quoted 5 lines
2. hcid and bluetoothd object path
What is the object path that you want use?
I suggested in an old email use a hierarchical paths. bluetoothd can be the main object path provided at /org/bluez/bluetoothd, hci D-Bus services could be provided at /org/bluez/bluetoothd/hci
The general idea is to abstract from any daemon names or Bluetooth specification details. This makes it possible to reuse this interface with FreeBSD in the future.
Quoted 5 lines
3. D-Bus services
hci D-BUS services is the next step, I am going to starting coding ASAP. Regarding inquiry requests, what kind of implementation do you prefer, send method reply message or send only signals(like the current)?
We can do both, but I think signals should be preferred. This allows graphical applications to dynamically update their lists.
Quoted 6 lines
If you use signals, all D-Bus client capturing D-Bus hci signals are able to see the new devices found. Using a method reply only the peer (requestor) will receive. Using a method reply approach, we can implement device class filters and avoid repeated devices. We have the same problem for remote name, disconnect, authentication/security, info, role switch and display connections.
We should keep an eye on security, but the idea is to send stuff to everybody that is interested in it.
Quoted 10 lines
4. bluetoothd
There are shared codeslike(pand/bnep.c, pand/sdp.c, hidd/sdp.c, ...)that we need be aware.
It is NOT clear for me how hcid and bluetoothd should work. hcid must be running all the time, but the hci D-Bus service will be running only if the system has a D-Bus system daemon running. Therefore, who should register the hci object path? IMHO, bluetoothd should centralize all D-Bus services. It will not be easy separate the "normal" code from the "D-Bus code". Maybe your "new interface" that your are defining can solve this problem.
Once bluetoothd is in place hcid would no longer be needed.
Quoted 3 lines
5. new interface
You said that a new interface for kernel and the userspace communication is being defined. What is the current status?
I am working on it.
Regards
Marcel
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[Claudio Takahasi]
Hi Marcel,
Quoted 40 lines · Marcel Holtmann
Hi Claudio,
Quoted 3 lines
You said in an old e-mail that hcid is your playground for D-Bus services. Probably, hcid D-Bus should be the starting point for bluetoothd.
since it is there and used, I think it is a good idea. At the moment it is optional and so we can test it. At some point I will make bluez-utils depend on D-Bus.
Quoted 16 lines
I would like to align your ideas to avoid future reworks.
D-Bus provides 4 types of messages:
1. Method call
2. Method reply
3. Signals
4. Error
Currently, only signals are sent. The following signals are sent as result of the hci commands:
- InquiryStart
- InquiryResult
- InquiryComplete
- RemoteName
path: /org/bluez/DevAgent
interface: org.bluez.DevAgentQuoted 4 lines
The topics that I want discuss are:
1. hcid signals
In my opinion it is not necessary send signals to notity inquiry start/complete. Only signals for news devices are enough.The idea behind also sending the InquiryStart and InquiryComplete events is that applications can show some graphical indications that the local device is now scanning for new devices in range. Since people can still call "hcitool scan" it is need for applications to know when someone else starts an inquiry.
Another aspect is, inquiry result can contain repeated devices. This
Quoted 7 lines
Quoted 4 lines
approach could cause D-Bus app client overhead(inconsistency), by other hand if periodic inquiry is active repeated signals must be sent because more than one client can be filtering these signals and they can start at different time. :)
And the RSSI values may changes in the repeated reponses. The clients must do the filtering. There is no other way.
[Claudio Takahasi]
Remember that we need cover normal inquiry and periodic inquiry. For periodic inquiry
I agree with this approach of send signals every time. We can implement a cache
to make the inquiry fast/powerful. Two or more clients can request inquiry at same
time, this is a normal scenario, but it can happen. For normal inquiry, we can't
use hci_inquiry because it a blocking operation. The inquiry must be integrated
in the main loop of the bluetoothd, using a HCI raw socket or the new interface that
your are defining.
Quoted 9 lines
2. hcid and bluetoothd object path
Quoted 4 lines
What is the object path that you want use?
I suggested in an old email use a hierarchical paths. bluetoothd can be the main object path provided at /org/bluez/bluetoothd, hci D-Bus services could be provided at /org/bluez/bluetoothd/hciThe general idea is to abstract from any daemon names or Bluetooth specification details. This makes it possible to reuse this interface with FreeBSD in the future.
[Claudio Takahasi]
I suggested previously use the bus name "org.bluez.bluetoothd", but do you think
relevant participate on freedesktop project?
The bus name could be "org.freedesktop.Bluez"
I don't know what are the advantages and which rules we need respect.
Quoted 8 lines
3. D-Bus services
Quoted 4 lines
hci D-BUS services is the next step, I am going to starting coding ASAP. Regarding inquiry requests, what kind of implementation do you prefer, send method reply message or send only signals(like the current)?
We can do both, but I think signals should be preferred. This allows graphical applications to dynamically update their lists.
[Claudio Takahasi]
I agree. We need define exactly which signals are necessary. I am going to update the specification document that I am writing and I will send you soon.
Quoted 21 lines
If you use signals, all D-Bus client capturing D-Bus hci signals are
Quoted 5 lines
able to see the new devices found. Using a method reply only the peer (requestor) will receive. Using a method reply approach, we can implement device class filters and avoid repeated devices. We have the same problem for remote name, disconnect, authentication/security, info, role switch and display connections.
We should keep an eye on security, but the idea is to send stuff to everybody that is interested in it.
Quoted 10 lines
4. bluetoothd
There are shared codeslike(pand/bnep.c, pand/sdp.c, hidd/sdp.c, ...)that we need be aware.
It is NOT clear for me how hcid and bluetoothd should work. hcid must be running all the time, but the hci D-Bus service will be running only if the system has a D-Bus system daemon running. Therefore, who should register the hci object path? IMHO, bluetoothd should centralize all D-Bus services. It will not be easy separate the "normal" code from the "D-Bus code". Maybe your "new interface" that your are defining can solve this problem.
Quoted 1 line
Once bluetoothd is in place hcid would no longer be needed.
[Claudio Takahasi]
hcid already contains the structure(main loop) required to register D-Bus services, it will be easy implement the D-Bus services.
Regarding sdpd, currently an application have to connect(sdp_connect) and stablish a session to register/update a service.
sdp D-Bus service shall be provided in the future, how do you think it should work in this new scenario?
Quoted 5 lines
5. new interface
Quoted 2 lines
You said that a new interface for kernel and the userspace communication is being defined. What is the current status?
I am working on it.
[Claudio Takahasi]
Where is the CVS branch? If possible, send me the address.
Regards
Quoted 16 lines
Marcel
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Marcel Holtmann
maintainerHi Claudio,
Quoted 5 lines
Remember that we need cover normal inquiry and periodic inquiry. For periodic inquiry
I agree with this approach of send signals every time. We can implement a cache
to make the inquiry fast/powerful. Two or more clients can request
Quoted 8 lines
inquiry at same
time, this is a normal scenario, but it can happen. For normal inquiry, we can't
usehci_inquirybecause it a blocking operation. The inquiry must be integrated
in the main loop of the bluetoothd, using a HCI raw socket or the new interface that
your are defining.
the kernel already has an inquiry cache. We can simply deliver that cache at the moment.
I am not going to duplicate the inquiry stuff inside bluetoothd. We will do it in hcid for now, but for bluetoothd the kernel should do all the work.
Quoted 7 lines
I suggested previously use the bus name "org.bluez.bluetoothd", but do you think
relevant participate on freedesktop project?The bus name could be "org.freedesktop.Bluez"
I don't know what are the advantages and which rules we need respect.
For now we will use "org.bluez" as base and I think about moving over to "org.bluetooth" and propose it as an additional standard. However that is not so important at the moment.
I like to use names that don't have any daemon names in it. This means that something like "org.bluez.bluetoothd" is bad if FreeBSD wants to provide a compat interface, but they don't call their daemon bluetoothd. So what I like to see is something like "org.bluetooth.device" and so on. Make it more logical. We don't even have to use the Bluetooth terminology. This includes HCI command names. In general I like to have an "discovery" procedure. This is doing an inquiry, a name resolve and the SDP service stuff. In case of EIR the inquiry response may deliver already enough information, because it can include a short name and a service UUID list.
Quoted 4 lines
I agree. We need define exactly which signals are necessary. I am going
to update the specification document that I am writing and I will send you soon.
My idea is to have multiple Bluetooth clients running at the same time and if one starts a new inquiry the others also got informed of these results. What they do with this results is their problem. I can draw a picture if needed, but I think my ideas behind it are clear.
Quoted 2 lines
hcid already contains the structure(main loop) required to register D-Bus services, it will be easy implement the D-Bus services.
Since I dropped D-Bus 0.23 support now, I am happy to accept any extensions to hcid.
Quoted 5 lines
Regarding sdpd, currently an application have to connect (
sdp_connect)
and stablish a session to register/update a service. sdp D-Bus service shall be provided in the future, how do you think it should work in this new scenario?
The SDP stuff is blocking at the moment and that is bad. My idea is to rewrite the SDP support and include it in bluetoothd. This means that it will be capable of caching SDP information and D-Bus clients can ask for service information quite easy. This is also important with the extended inquiry support, because the UUID list can be provided via an inquiry response. And of course bluetoothd should add the UUID of all registered services to the extended inquiry data when someone registers a new record via D-Bus.
Quoted 1 line
Where is the CVS branch? If possible, send me the address.
It will be in the GIT tree, when I have some spare time to clean it.
Regards
Marcel
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