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Date:   Fri, 6 Oct 2023 13:04:32 +0200
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     Max Filippov <jcmvbkbc@gmail.com>
Cc:     linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org,
        devicetree@vger.kernel.org, Jiri Slaby <jirislaby@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>,
        Ilpo =?iso-8859-1?Q?J=E4rvinen?= <ilpo.jarvinen@linux.intel.com>
Subject: Re: [PATCH v4 5/5] drivers/tty/serial: add ESP32S3 ACM device driver
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On Fri, Oct 06, 2023 at 03:27:37AM -0700, Max Filippov wrote:
> On Fri, Oct 6, 2023 at 2:34 AM Greg Kroah-Hartman
> > > > Yes, but not all do.  If you don't need to do anything special, it can
> > > > just claim to be a normal device, we've had threads about this on the
> > > > list before.  If you don't need to determine in userspace from the tty
> > > > connection what device it is, just use the default one instead.
> > >
> > > Ok, it looks like having
> > >
> > > #define PORT_ESP32ACM (-1)
> > >
> > > in the driver source should be ok? I've tested that it works.
> >
> > Hah, I like that hack.  But why not just use PORT_UNKNOWN?
> 
> A lot of functionality doesn't work with PORT_UNKNOWN, e.g.
> console or modem control.
> I've got the idea of using -1 from this email:
> https://lore.kernel.org/linux-serial/502240f7-2cac-4fe6-9e27-f9861db3666d@app.fastmail.com/

Ok, we should encode this as a "real" number, "PORT_ANY" and set it to
-1 and let all new devices use it.

thanks,

greg k-h