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

[Jiri Slaby]

On 21. 06. 25, 21:08, Andy Shevchenko wrote:
> 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].

Right, I was confused too, but then I noticed there is:
  uart->port.type = up->port.type;
in between the tests.

> > 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.

ACK, I will.

--
js
suse labs