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

[Maciej S. Szmigiero]

On 18.06.2025 07:48, Andy Shevchenko wrote:
> On Wed, Jun 11, 2025 at 12:03:16PM +0200, Jiri Slaby (SUSE) wrote:
> > There is no point in a long 'if' in serial8250_register_8250_port() to
> > just return ENOSPC for PORT_8250_CIR ports. Invert the condition and
> > return immediately.
> >
> > 'gpios' variable was moved to its set location.
> >
> > And return ENODEV instead of ENOSPC. The latter is a leftover from the
> > previous find-uart 'if'. The former makes a lot more sense in this case.
>
> ...
>
> > +	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.

Thanks,
Maciej

[1]: https://lore.kernel.org/lkml/c599065a-60f5-070e-c1e3-12b3ab2cbf0a@xxxxxxxx/