Re: [Bluez-devel] how to do inquiry with RSSI in bluetooth 1.2 devices?

[Marcel Holtmann <marcel@holtmann.org>]

Hi Albert,

> I'd like to use bluez to perform a device inquiry with RSSI using a
> bluetooth 1.2 device.  Currently, I'm using an Anycom USB-120
> bluetooth adapter with the latest firmware installed.
> 
> I want to check the inquiry mode of the bluetooth device first and
> then change it if needed.  Based on my reading of the bluez headers
> and the bluetooth spec, this is what I came up with.
> 
>         // first read the current mode and see if we need to change it
>         {
>             struct hci_request req;
>             char raw_rp[EVT_CMD_COMPLETE_SIZE + READ_INQUIRY_MODE_RP_SIZE];
>             read_inquiry_mode_rp *rp;
> 
>             req.ogf = OGF_LINK_CTL;
>             req.ocf = OCF_READ_INQUIRY_MODE;
>             req.cparam = 0;
>             req.clen = 0;
>             req.rparam = &raw_rp;
>             req.rlen = READ_INQUIRY_MODE_RP_SIZE;
> 
>             err = hci_send_req( sock, &req, 0 );
>             if( err ) {
>                 if( errno == EPERM ) {
>                     fprintf(stderr, "permission denied while reading inquiry "
>                             "mode.  Are you sure you're superuser?\n");
>                 }
>                 return -1;
>             }
> 
>             rp = (read_inquiry_mode_rp*)(raw_rp + EVT_CMD_COMPLETE_SIZE);
>             if( rp->status != 0 ) {
>                 fprintf(stderr, "error 0x%x reading inquiry mode\n", 
>                         rp->status);
>                 return -1;
>             }
>             change_inquiry_mode = (! rp->mode);
> 
>             fprintf(stderr, "done reading inquiry mode.  %s to set\n",
>                     change_inquiry_mode?"Need":"Do not need");
>         }
> 
>         // set the inquiry mode (use RSSI or not) if needed
>         if( change_inquiry_mode )
>         {
>             write_inquiry_mode_cp wim_cp;
>             struct hci_request req;
>             char raw_rp[EVT_CMD_COMPLETE_SIZE + WRITE_INQUIRY_MODE_RP_SIZE];
>             write_inquiry_mode_rp *rp;
>             wim_cp.mode = do_inquiry_with_rssi;
> 
>             req.ogf = OGF_LINK_CTL;
>             req.ocf = OCF_WRITE_INQUIRY_MODE;
>             req.event = EVT_CMD_COMPLETE;
>             req.cparam = &wim_cp;
>             req.clen = WRITE_INQUIRY_MODE_CP_SIZE;
>             req.rparam = &raw_rp;
>             req.rlen = EVT_CMD_COMPLETE_SIZE + WRITE_INQUIRY_MODE_RP_SIZE;
> 
>             err = hci_send_req( sock, &req, 0 );
>             if( err ) { 
>                 fprintf(stderr, "error while setting inquiry mode.  errno %d\n",
>                         errno);
>                 perror("hci_send_cmd"); 
>                 return -1;
>             }
> 
>             rp = (write_inquiry_mode_rp*)(raw_rp + EVT_CMD_COMPLETE_SIZE);
>             if( rp->status != 0 ) {
>                 fprintf(stderr, "error 0x%x setting inquiry mode\n",
>                         rp->status);
>                 return -1;
>             }
> 
>             fprintf(stderr, "Done setting inquiry mode\n");
>         }
> 
> My first question is - is this the correct way to do it?

looks like it is correct. Send me a patch for the Bluetooth library to
include this as API functions.

> When I run this with the anycom bluetooth device, the very first
> hci_send_req never returns.  I expected the READ_INQUIRY_MODE command
> to generate a CMD_COMPLETE event, but no event is ever generated (I
> tested this separately).  Also, when hcidump is run concurrently with
> this program, it doesn't pick anything up (no events are read by
> hcidump)  The same happens if I try to set the inquiry mode directly
> without reading it first (the WRITE_INQUIRY_MODE command never
> returns)

I never saw that on my dongle. Please recompile your kernel without the
SCO audio support for the hci_usb driver. What kind of USB host
controller are you using? What kernel version do you use?

Regards

Marcel




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