Bluetooth connection hangs after some retries (reset required/possible?)

Bluetooth connection hangs after some retries (reset required/possible?)

[Manuel Reimer]

Hello,

I'm still doing my first steps with bluetooth on Linux...

I'm trying to get HID reports of a bluetooth game controller (PS4 
gamepad). The relevant lines:

char dest[18] = "XX:XX:XX:XX:XX:XX";
int int_socket = socket(AF_BLUETOOTH, SOCK_SEQPACKET, BTPROTO_L2CAP);
struct sockaddr_l2 addr = { 0 };
addr.l2_family = AF_BLUETOOTH;
str2ba( dest, &addr.l2_bdaddr );
addr.l2_psm = htobs(L2CAP_PSM_HIDP_INTR);
connect(int_socket, (struct sockaddr *)&addr, sizeof(addr));
char buf[79] = { 0 };
int bytes_read;
bytes_read = recv(int_socket, buf, sizeof(buf), 0);
while(1) {
   if( bytes_read > 0 ) {
     printf("received [%s]\n", buf);
   }
}

Yes, I do proper initialization and yes, my "real code" has error handling.

If I run this code for the first time (currently I have the "hidp" 
module blacklisted to get sure I'm really the first user of the device), 
then everything works as expected. Initialization is done and lines are 
running through console.

Sometimes I'm able to Ctrl+C and restart *once* but it never is possible 
to do a third try. If I do so, then the "read" just hangs forever. This 
also happens if I disconnect the bluetooth device and reconnect it. I 
have to "systemctl restart bluetooth" in this case to get a new chance.

What is happening here? For me it seems like the bluetooth daemon 
"somehow" does some kind of "deadlocking". Maybe the controller keeps 
sending and noone takes the messages which causes the daemon to deadlock?

How to get around this? Is it actually possible to get this stable? Is 
there, for example, some command, I can send, so whatever hangs here is 
reset?

Thank you for every answer...

Best regards,

Manuel

Re: Bluetooth connection hangs after some retries (reset required/possible?)

[Manuel Reimer]

On 03/04/2016 04:09 PM, Manuel Reimer wrote:
> Hello,
>
> I'm still doing my first steps with bluetooth on Linux...
>
> I'm trying to get HID reports of a bluetooth game controller (PS4
> gamepad). The relevant lines:
>
> char dest[18] = "XX:XX:XX:XX:XX:XX";
> int int_socket = socket(AF_BLUETOOTH, SOCK_SEQPACKET, BTPROTO_L2CAP);
> struct sockaddr_l2 addr = { 0 };
> addr.l2_family = AF_BLUETOOTH;
> str2ba( dest, &addr.l2_bdaddr );
> addr.l2_psm = htobs(L2CAP_PSM_HIDP_INTR);
> connect(int_socket, (struct sockaddr *)&addr, sizeof(addr));
> char buf[79] = { 0 };
> int bytes_read;
> bytes_read = recv(int_socket, buf, sizeof(buf), 0);
> while(1) {
>    if( bytes_read > 0 ) {
>      printf("received [%s]\n", buf);
>    }
> }
>
> Yes, I do proper initialization and yes, my "real code" has error handling.
>
> If I run this code for the first time (currently I have the "hidp"
> module blacklisted to get sure I'm really the first user of the device),
> then everything works as expected. Initialization is done and lines are
> running through console.
>
> Sometimes I'm able to Ctrl+C and restart *once* but it never is possible
> to do a third try. If I do so, then the "read" just hangs forever. This
> also happens if I disconnect the bluetooth device and reconnect it. I
> have to "systemctl restart bluetooth" in this case to get a new chance.
>
> What is happening here? For me it seems like the bluetooth daemon
> "somehow" does some kind of "deadlocking". Maybe the controller keeps
> sending and noone takes the messages which causes the daemon to deadlock?
>
> How to get around this? Is it actually possible to get this stable? Is
> there, for example, some command, I can send, so whatever hangs here is
> reset?
>
> Thank you for every answer...
>
> Best regards,
>
> Manuel
> --
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I did a few more tries.

This is a "hcidump -x" of one connection from usermode. It sends out one 
report (setting the LEDs on the controller) and successfully receives 10 
HID reports. For whatever reason I don't see all 10 in the hcidump output...

http://pastebin.com/50g2nMWF

And this one is a dump of the "deadlocked" case:

http://pastebin.com/QKWp8E2G

In general both logs look much more "dirty" as a dump created with the 
kernel module (hidp) attached...

Any help would be very welcome. Maybe someone can at least point me to a 
different mailing list where someone may know how to do "stable usermode 
bluetooth programming"?

Thank you very much in advance.

Best regards,

Manuel