linux-kernel - Re: [PATCH v2] tty: nozomi: tty_unregister_device -> tty_port_unregister

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Message-ID: <CAD-N9QXD85YthmKp_AGjVzXL4=NstCvicEdVO_zu=TSj0kMSZw@mail.gmail.com>
Date:   Wed, 21 Jul 2021 21:35:31 +0800
From:   Dongliang Mu <mudongliangabcd@...il.com>
To:     Johan Hovold <johan@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>, stable@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...e.de>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] tty: nozomi: tty_unregister_device -> tty_port_unregister_device

On Wed, Jul 21, 2021 at 9:09 PM Johan Hovold <johan@...nel.org> wrote:
>
> On Wed, Jul 21, 2021 at 08:53:47PM +0800, Dongliang Mu wrote:
> > On Wed, Jul 21, 2021 at 8:01 PM Johan Hovold <johan@...nel.org> wrote:
> > >
> > > On Wed, Jul 21, 2021 at 07:33:04PM +0800, Dongliang Mu wrote:
> > > > The pairwise api invocation of tty_port_register_device should be
> > > > tty_port_unregister_device, other than tty_unregister_device.
> > >
> > > Are you sure about that? Please explain why you think this to be the
> > > case and why this change is needed.
> >
> > I am sure about this.
>
> I'm afraid you are mistaken. There is a bit of inconsistency in the API,
> but it is *not* a requirement to use the port helper for deregistration
> here.
>
> > 1. From the implementation,
> >     tty_port_register_device -> tty_port_register_device_attr ->
> > tty_port_link_device; tty_register_device_attr
> >     tty_register_device -> tty_register_device_attr
> >
> >     tty_port_unregister_device -> serdev_tty_port_unregister;
> > tty_unregister_device
> >     tty_unregister_device
>
> >     As to the functionability, tty_port_register_device pairs with
> > tty_port_unregister_device; meanwhile, the same to tty_register_device
> > and tty_unregister_device.
>
> Again, this is not an explanation. Why do think it is needed? What could
> possibly go wrong if you don't change the code like you propose?
>
> > 2. From the function naming style,
> >
> >     tty_port_register_device - tty_port_unregister_device;
> > tty_register_device - tty_unregister_device
>
> Yes, the naming suggests you should be using the port helper and it is
> ok to do so, but again, it is not a requirement (unless you're using the
> serdev variant).

OK, I see. Thanks for your information.

Next time I will double-check the underlying details of each function
to verify if they are in pairs.

>
> > > > Fixes: a6afd9f3e819 ("tty: move a number of tty drivers from drivers/char/ to drivers/tty/")
> > >
> > > Please try a little harder, that's clearly not the commit that changed
> > > to the port registration helper.
> > >
> > > > Cc: stable@...r.kernel.org
> > >
> > > Why do you think this is stable material? (hint: it is not)
> >
> > From the documentation, this label could make the patch automatically
> > go to stable tree. And stable tree is also using the incorrect api.
>
> No, it is not using an "incorrect api". There is nothing wrong with
> current code. And it certainly does not need to be changed in stable.
>
> Johan