[Bluez-devel] Host to Host Controller flow control

[Bluez-devel] Host to Host Controller flow control

[Catalin Drula]

Hi Marcel,

I was succesful in writing a patch for handling the Hardware Error event. I have
an iPAQ h5550 with a buggy Bluetooth module from RTX Telecom. I have done some
tests after applying the patch and everything seems to be going smooth (whenever
the HW error event occurs, the application sees a "connection abort" and
synchronization is automatically regained). I will post it tomorrow along with
more detailed explanation.

I wanted to take a shot at implementing host-to-controller flow control for 
Bluez. Before I start, it'd be great to have your thoughts on this.

Thanks,

Catalin



-------------------------------------------------------
SF email is sponsored by - The IT Product Guide
Read honest & candid reviews on hundreds of IT Products from real users.
Discover which products truly live up to the hype. Start reading now.
http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click
_______________________________________________
Bluez-devel mailing list
Bluez-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/bluez-devel

[Bluez-devel] Re: Host to Host Controller flow control

[Catalin Drula]

Catalin Drula <catalin.drula <at> imag.fr> writes:

> I wanted to take a shot at implementing host-to-controller flow control for
> Bluez. Before I start, it'd be great to have your thoughts on this.

Hi Marcel,

I've been looking over the code in hci_core.c and hci_event.c, in particular,
hci_tx_task, hci_sched_acl, hci_sched_sco, hci_low_sent and 
hci_num_comp_pkts_evt.

It seems like we're already doing host to host controller flow control, 
as far as I could tell. At the very least, we're correctly keeping track 
of the number of free slots in the controller's buffers and we're never
overflowing it. Also hci_low_sent always selects the connection with the
most completed packets so there seems to be some balancing done there. 
Could you point out what is missing (the reason this item is on the TODO list)?

Thanks,

Catalin



-------------------------------------------------------
SF email is sponsored by - The IT Product Guide
Read honest & candid reviews on hundreds of IT Products from real users.
Discover which products truly live up to the hype. Start reading now.
http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click
_______________________________________________
Bluez-devel mailing list
Bluez-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/bluez-devel

Re: [Bluez-devel] Re: Host to Host Controller flow control

[Marcel Holtmann]

Hi Catalin,

> I've been looking over the code in hci_core.c and hci_event.c, in particular,
> hci_tx_task, hci_sched_acl, hci_sched_sco, hci_low_sent and 
> hci_num_comp_pkts_evt.
> 
> It seems like we're already doing host to host controller flow control, 
> as far as I could tell. At the very least, we're correctly keeping track 
> of the number of free slots in the controller's buffers and we're never
> overflowing it. Also hci_low_sent always selects the connection with the
> most completed packets so there seems to be some balancing done there. 
> Could you point out what is missing (the reason this item is on the TODO list)?

the host to host controller flow control means that we tell the chip to
use flow control. This is the other way around and we don't support it
at the moment, because it is easy for us to handle big packets. If you
enable host to host controller flow control you need to tell the chip
when you are ready to receive more packets.

Regards

Marcel




-------------------------------------------------------
SF email is sponsored by - The IT Product Guide
Read honest & candid reviews on hundreds of IT Products from real users.
Discover which products truly live up to the hype. Start reading now.
http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click
_______________________________________________
Bluez-devel mailing list
Bluez-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/bluez-devel

[Bluez-devel] Re: Host to Host Controller flow control

[Catalin Drula]

Hi Marcel,

Marcel Holtmann <marcel <at> holtmann.org> writes:
 
> the host to host controller flow control means that we tell the chip to
> use flow control. This is the other way around and we don't support it
> at the moment, because it is easy for us to handle big packets. If you
> enable host to host controller flow control you need to tell the chip
> when you are ready to receive more packets.

Ok, but I think what we are missing then is called "host controller to host flow
control" or as in the specification "flow control... in the direction from the
Host Controller to the Host". Even the command that enables this is called
Set_Host_Controller_To_Host_Flow_Control.

Correct me if I am wrong, but I think you should update the TODO list to say

* Host Controller to Host flow control

Catalin 






-------------------------------------------------------
SF email is sponsored by - The IT Product Guide
Read honest & candid reviews on hundreds of IT Products from real users.
Discover which products truly live up to the hype. Start reading now.
http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click
_______________________________________________
Bluez-devel mailing list
Bluez-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/bluez-devel

Re: [Bluez-devel] Re: Host to Host Controller flow control

[Marcel Holtmann]

Hi Catalin,

> > the host to host controller flow control means that we tell the chip to
> > use flow control. This is the other way around and we don't support it
> > at the moment, because it is easy for us to handle big packets. If you
> > enable host to host controller flow control you need to tell the chip
> > when you are ready to receive more packets.
> 
> Ok, but I think what we are missing then is called "host controller to host flow
> control" or as in the specification "flow control... in the direction from the
> Host Controller to the Host". Even the command that enables this is called
> Set_Host_Controller_To_Host_Flow_Control.
> 
> Correct me if I am wrong, but I think you should update the TODO list to say

I looked it up in the Bluetooth 2.0 specification and it is now called
Set_Controller_To_Host_Flow_Control and this means that the todo list
should talk about "Host Flow Control", because this is what is missing.

Regards

Marcel




-------------------------------------------------------
SF email is sponsored by - The IT Product Guide
Read honest & candid reviews on hundreds of IT Products from real users.
Discover which products truly live up to the hype. Start reading now.
http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click
_______________________________________________
Bluez-devel mailing list
Bluez-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/bluez-devel