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References: <20230928151631.149333-1-jcmvbkbc@gmail.com> <20230928151631.149333-6-jcmvbkbc@gmail.com>
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From:   Rob Herring <robh+dt@kernel.org>
Date:   Fri, 6 Oct 2023 09:11:15 -0500
Message-ID: <CAL_Jsq+P9VAv1uSn=sU1J7Q-=mgFBFiOj7EkgncnrQwhWGQETA@mail.gmail.com>
Subject: Re: [PATCH v4 5/5] drivers/tty/serial: add ESP32S3 ACM device driver
To:     Max Filippov <jcmvbkbc@gmail.com>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org,
        devicetree@vger.kernel.org, Jiri Slaby <jirislaby@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>,
        =?UTF-8?Q?Ilpo_J=C3=A4rvinen?= <ilpo.jarvinen@linux.intel.com>
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On Tue, Oct 3, 2023 at 2:47=E2=80=AFPM Max Filippov <jcmvbkbc@gmail.com> wr=
ote:
>
> On Tue, Oct 3, 2023 at 5:55=E2=80=AFAM Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> wrote:
> >
> > On Thu, Sep 28, 2023 at 08:16:31AM -0700, Max Filippov wrote:
> > > Add driver for the ACM  controller of the Espressif ESP32S3 Soc.
> >
> > Odd extra space :(
>
> Ok.
>
> > > Hardware specification is available at the following URL:
> > >
> > >   https://www.espressif.com/sites/default/files/documentation/esp32-s=
3_technical_reference_manual_en.pdf
> > >   (Chapter 33 USB Serial/JTAG Controller)
> >
> > I don't understand this driver, "ACM" is a USB host <-> gadget protocol=
,
> > why do you need a platform serial driver for this?
>
> The USB part of this piece of hardware is fixed and not controllable, so
> all we have is a very limited UART interface. But to the outside world
> it's a USB device with the CDC-ACM interface.
>
> > > diff --git a/drivers/tty/serial/esp32_acm.c b/drivers/tty/serial/esp3=
2_acm.c
> > > new file mode 100644
> > > index 000000000000..f02abd2ac65e
> > > --- /dev/null
> > > +++ b/drivers/tty/serial/esp32_acm.c
> > > @@ -0,0 +1,459 @@
> > > +// SPDX-License-Identifier: GPL-2.0-or-later
> >
> > Why "or later"?  I have to ask, sorry.
>
> I don't really have a preference here. Is there a reason to choose
> GPL-2.0 only for a new code?

Yes, that's the default license for the kernel. So you should have a
reason for picking something else. Like maybe you copied all this from
somewhere else and that was the license.

Rob