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Date: Thu, 12 Jan 2017 15:49:14 +0100
From: Johan Hovold <johan@kernel.org>
To: Russell Senior <russell@personaltelco.net>
Cc: Johan Hovold <johan@kernel.org>,
        Aidan Thornton <makosoft@gmail.com>,
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Subject: Re: [PATCH 06/13] USB: serial: ch341: fix initial line settings
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On Mon, Jan 09, 2017 at 02:51:59PM +0100, Johan Hovold wrote:
> On Tue, Dec 20, 2016 at 09:49:00PM +0100, Johan Hovold wrote:
> > On Tue, Dec 20, 2016 at 12:09:55PM -0800, Russell Senior wrote:
> > > On Tue, Dec 20, 2016 at 8:07 AM, Johan Hovold <johan@kernel.org> wrote:
> > > 
> > > > Perhaps we should determine what else is working or broken first,
> > > > though.
> > > >
> > > > Russel, could you test if break-signalling works, and if the
> > > > modem-control signals (DTR/RTS) are asserted at open? Do you get any
> > > > interrupts when the modem-status changes (e.g. remote end hangs up --
> > > > there should be debug messages)?
> > > 
> > > Which version(s) would you like tested?
> > 
> > You can use c51087107e88 ("USB: serial: ch341: rename modem-status
> > register").
> 
> As you noticed, I decided to revert to using direct register writes to
> avoid having the modem-control lines being toggled on open/set_termios.
> So with a trivial patch changing the initial LCR settings your device
> should now be supported.

I received one of these quirky devices today and discovered that the
partial revert to using direct register writes should be sufficient for
basic support for these devices.

Changing baud rate and line settings (e.g. 6E2) works with my fixes for
4.10-rc4.

> It would still be interesting to know whether the features mentioned
> above works. Testing that using the series I posted on Friday would be
> preferred (but not required).

I did a quick test of this as well, and it seems break control is not
supported and no interrupts are received on modem-status changes. DTR
and RTS appear to work at least.

Johan