2005-03-25 12:01:18

by Catalin Drula

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

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






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2005-03-25 12:27:31

by Marcel Holtmann

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

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




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2005-03-25 11:48:03

by Marcel Holtmann

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

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




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