Re: [PATCH 30/33] serial: 8250: invert serial8250_register_8250_port() CIR condition

Andy Shevchenko
2025-06-21T19:09:54Z

Fri, Jun 20, 2025 at 11:48:09PM +0200, Maciej S. Szmigiero kirjoitti:
> On 18.06.2025 07:48, Andy Shevchenko wrote:
> > On Wed, Jun 11, 2025 at 12:03:16PM +0200, Jiri Slaby (SUSE) wrote:

...

> > > + if (uart->port.type == PORT_8250_CIR) {
> > > + ret = -ENODEV;
> > > + goto unlock;
> > > + }
> >
> > > + if (up->port.flags & UPF_FIXED_TYPE)
> > > + uart->port.type = up->port.type;
> >
> > > + if (uart->port.type != PORT_8250_CIR) {
> >
> > I admit that there tons of mysterious ways of UART initialisation, but can you
> > elaborate how this is not a always-true conditional?
>
> Careful here, someone had an idea in the past that this is indeed
> a dead code/branch and ended causing a regression [1].

> It would definitely make sense to add a comment describing the code
> flow there though as it proven to bewilder people.

Yes, this is my point between the lines. I left the code that may affect the
type change and the second check needs a comment explaining these cases, if any.
"If any" defines "always-true" or not conditional. W//o a comment this code
tends to be updated again and lead to a regression.

--
With Best Regards,
Andy Shevchenko