Re: [Bluez-devel] Reading RSSI of non-connected devices

[Marcel Holtmann <marcel@holtmann.org>]

Hi Andreas,

> We are trying to programmatically read the signal strength of Bluetooth 
> devices at discovery time (not only for connections). Seeing through the 
> source code it appears that in some cases (BT 1.2?) an inquiry gets an 
> HCI response that includes the RSSI (struct inquiry_info_with_rssi). 
> This information appears to be cached in struct inquiry_data if 
> available, 0 otherwise. However the only way to access this information 
> seems to be to get a pointer to a hci_dev struct (e.g. through 
> hci_dev_get(int index)) and use its inq_cache member? Getting this 
> information from the client side is not possible right now?
> 
> As I understand it from the code, the libBluetooth.so library does an 
> ioctl on an HCI socket with specific predefined commands such as HCIINQUIRY.
> How should we go about adding the functionality we need? Would we need 
> to define a custom HCI socket command and handle it somewhere in a 
> customized Kernel module? Or is there an easier way?

the ioctl() is very old and number updated it to support Inquiry with
RSSI or Extended Inquiry. The main reason for this is, because you can't
update it without breaking backward-compatibility with older versions of
the library and the tools.

However you can program the HCI socket interface directly and read the
inquiry result directly. Example code for this is already available in
the mailing list archives.

Regards

Marcel




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