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Subject: Re: btattach and 3wire doesn't work
From: Marcel Holtmann <marcel@holtmann.org>
In-Reply-To: <CAO1O6sewvkB=j5cfSXMbjHsZi3BmyD=CqcCFpKypQ6HEvmj99g@mail.gmail.com>
Date: Wed, 20 Sep 2017 17:50:44 +0200
Cc: Bluez mailing list <linux-bluetooth@vger.kernel.org>
Message-Id: <5467450F-B5AA-4BD5-874F-2ABC7F05D821@holtmann.org>
References: <CAO1O6sewvkB=j5cfSXMbjHsZi3BmyD=CqcCFpKypQ6HEvmj99g@mail.gmail.com>
To: Emil Lenngren <emil.lenngren@gmail.com>
Sender: linux-bluetooth-owner@vger.kernel.org
List-ID: <linux-bluetooth.vger.kernel.org>

Hi Emil,

> I'm trying to use the new btattach utility to attach a controller
> which uses the 3-wire UART protocol. The older hciattach works great
> but btattach doesn't.
> This is the command I use including the output:
> 
> # btattach -B /dev/ttyS1 -P 3wire -S 500000
> Attaching Primary controller to /dev/ttyS1
> Switched line discipline from 0 to 15
> Failed to get device id: Protocol driver not attached
> No controller attached
> 
> By reading the source at
> https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/tools/btattach.c
> I see that it differs a bit from hciattach. Notably, it calls the
> HCIUARTGETDEVICE ioctl function directly after the HCIUARTSETPROTO
> ioctl call. The hciattach utility does not use HCIUARTGETDEVICE at
> all.
> 
> The cause of the problem is that when using 3wire, the hci does not
> get registered immediately (which btattach thinks) but instead after
> the handshake is complete.
> 
> If I run btattach in gdb and break before the HCIUARTGETDEVICE ioctl
> call, wait a few seconds and then resume, it works as expected. What
> is the purpose of HCIUARTGETDEVICE? I see it's only being used when
> the Raw option is used (which is by the way not mentioned in the Usage
> docs).
> 
> Another issue I have is that hciattach/btattach only support a few
> different baud rates. I want to use 750000 bit/s. Is there a purpose
> of only allowing some? Currently I use hciattach with a dummy baud
> rate followed by
> https://gist.github.com/lategoodbye/f2d76134aa6c404cd92c and that
> works.

which hardware is this? I always wanted to fix some of the 3-wire support to make sure it fully works with btattach and everything is done inside the kernel correctly. Including proper support for hdev->setup for vendor firmware loading etc.

Regards

Marcel