Re: Detecting end of GSM datacall

["Timo Teräs" <ext-timo.teras@nokia.com>]

ext James Carlson wrote:
> Timo Teräs writes:
>>I tracked down the reason: since the PPP link is between PC and remote 
>>computer, the mobile phone does not send any PPP packets that the link 
>>is dead. Instead it just sends '\r\nNO CARRIER\r\n'. And leaves the 
>>Bluetooth connection in AT command mode. Thus PPP stays happily up.
> 
> Why doesn't it de-assert DCD (Data Carrier Detect) and thus cause pppd
> to receive SIGHUP as expected?
> 
> In my opinion, we shouldn't really go too far out of our way to make
> fatally compromised interfaces work "right."

Actually this is a very good question. I now finally solved this bug. It 
appears that BlueZ correctly translates/transports the carrier detect 
signal from my mobile. However it does not call tty_hangup() when the 
carrier detect is de-asserted. I managed to get this working perfectly 
well by adding one if () and tty_hangup() call to 
net/bluetooth/rfcomm/tty.c.

So this is actually a BlueZ emulation bug. I'll post bug report / simple 
patch to appropriate list asap.

Thanks,
   Timo