[Bluez-devel] Lower granularity for INQUIRY interval

[Bluez-devel] Lower granularity for INQUIRY interval

[Catalin Drula]

Hi,

Is there a way to perform INQUIRY for intervals with
a lower granularity than 1.28 seconds? I know the Bluetooth
specification says no.

The solution that I found was to use the INQUIRY_CANCEL command
before the expiration of the inquiry interval. At a programming
level in order to do this I need to work at the HCI level (since the
API function hci_inquiry is blocking, cannot be interrupted).
Is there any other way to do this?

Could we potential have a new function in the API, say
hci_inquiry_fine_granularity, that does exactly what I described
above?

At the Bluetooth hardware level (if there is anyone that has such
knowledge) does my solution of issuing an INQUIRY CANCEL command before
the expiration of the INQUIRY interval really work? (I have a hunch
that the hardware might stay in INQUIRY mode anyway until the end of the
current 1.28sec time slot).

Thanks for any advice,

Catalin



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Re: [Bluez-devel] Lower granularity for INQUIRY interval

[Steven Singer]

Catalin Drula wrote:
> Is there a way to perform INQUIRY for intervals with
> a lower granularity than 1.28 seconds? I know the Bluetooth
> specification says no.

To inquire for less than 10.24 seconds is a bad idea. Unless you
inquire for a single contiguous block lasting 10.24 seconds you do not
have a good probability of picking up all devices.

Note that, for example, 8 consecutive 1.28 second inquiries is not
guaranteed to work.

> Could we potential have a new function in the API, say
> hci_inquiry_fine_granularity, that does exactly what I described
> above?

I don't think that it's a good idea to add an API to make it easy to
perform actions that are bad ideas.

> At the Bluetooth hardware level (if there is anyone that has such
> knowledge) does my solution of issuing an INQUIRY CANCEL command before
> the expiration of the INQUIRY interval really work? (I have a hunch
> that the hardware might stay in INQUIRY mode anyway until the end of the
> current 1.28sec time slot).

CSR devices will stop inquiring straight away (give or take a few
milliseconds). I can't comment on what other manufacturers will do.

	- Steven
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Re: [Bluez-devel] Lower granularity for INQUIRY interval

[Marcel Holtmann]

Hi Steven,

> > Could we potential have a new function in the API, say
> > hci_inquiry_fine_granularity, that does exactly what I described
> > above?
> 
> I don't think that it's a good idea to add an API to make it easy to
> perform actions that are bad ideas.

I will never add such a specific API, but actually there is already one
for these kind of things. It is called HCI raw socket ;)

Regards

Marcel




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