From: Catalin Drula <Catalin.Drula@imag.fr>
To: <bluez-devel@lists.sourceforge.net>
Message-ID: <Pine.GSO.4.33.0503171103450.12042-100000@horus.imag.fr>
MIME-Version: 1.0
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Subject: [Bluez-devel] Handling a Hardware Error event on iPAQ h5550
Sender: bluez-devel-admin@lists.sourceforge.net
Errors-To: bluez-devel-admin@lists.sourceforge.net
Reply-To: bluez-devel@lists.sourceforge.net
Date: Thu, 17 Mar 2005 11:23:19 +0100 (CET)

Hi,

I was trying to debug the Bluetooth subsystem on an HP iPAQ h5550 running
Linux:

root@h3900:~# hciconfig -a
hci0:   Type: UART
        BD Address: 08:00:17:1A:EB:76 ACL MTU: 339:4 SCO MTU: 60:9
        UP RUNNING PSCAN ISCAN
        RX bytes:-2117082264 acl:19904935 sco:0 events:4940395 errors:0
        TX bytes:386017560 acl:9879838 sco:0 commands:430 errors:0
        Features: 0xff 0x3b 0x05 0x00 0x00 0x00 0x00 0x00
        Packet type: DM1 DM3 DM5 DH1 DH3 DH5 HV1 HV2 HV3
        Link policy:
        Link mode: SLAVE ACCEPT
        Name: 'POCKET_PC'
        Class: 0x000000
        Service Classes: Unspecified
        Device Class: Miscellaneous,
        HCI Ver: 1.1 (0x1) HCI Rev: 0x180 LMP Ver: 1.1 (0x1) LMP Subver: 0x180
        Manufacturer: RTX Telecom A/S (21)

The problem I am facing on this machine is that it seems that the UART
communication is sometimes unreliable. What happens is that while sending
data, there sometimes seems to be corruption between the host and the
controller. For example, doing an l2test where the iPAQ is sending to a
PC, every once in a while on the receiving side there are data or sequence
or size mismatches. After a while, the corrupted bytes happen to be in the
H4 header, and the controller assumes it has lost synchronization with the
host, thus sending a "Hardware Error" event. It then expects a "Reset"
command to resynchronize.

Since a lot of digging has not found the root cause of these errors in the
UART communication, I wanted to hack the Bluez stack to better handle when
these loss of synchronization events occur (I am not refering to patching
the main Bluez stack, but rather make a hack for our own purposes here,
and perhaps share it with other iPAQ h5550 users).

It is easy enough to add the sending of a "Reset" command after a
"Hardware Error" event is received, but I get the impression that there's
more needed, such as tearing down the established connections somehow. The
point is to get a "clean" stack to start with after such an event (and of
course, propagate the error up the stack so that the application gets a
"broken connection"). Any advice on how hard it is to do that, and what
needs to be done?

Currently, what happens is that after sending "Reset", we resynchronize
with the controller, but the previous connections still show:

root@h3900:~# hcitool con
Connections:
        < ACL 00:10:DC:57:C9:79 handle 1 state 8 lm MASTER
        > ACL 08:00:17:1A:E6:02 handle 2 state 8 lm SLAVE

Thanks in advance for your help,

Catalin


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