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SubjectRe: [PATCH] serial: 8250: add option to disable registration of legacy ISA ports
On Sun, Jan 31, 2021 at 01:18:47PM +0000, Måns Rullgård wrote:
> Greg Kroah-Hartman <gregkh@linuxfoundation.org> writes:
>
> > On Thu, Jan 28, 2021 at 05:22:44PM +0000, Mans Rullgard wrote:
> >> On systems that do not have the traditional PC ISA serial ports, the
> >> 8250 driver still creates non-functional device nodes. This change
> >> makes only ports that actually exist (PCI, DT, ...) get device nodes.
> >>
> >> Signed-off-by: Mans Rullgard <mans@mansr.com>
> >> ---
> >> drivers/tty/serial/8250/8250_core.c | 26 ++++++++++++++++++++------
> >> drivers/tty/serial/8250/Kconfig | 5 +++++
> >> 2 files changed, 25 insertions(+), 6 deletions(-)
> >>
> >> diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
> >> index cae61d1ebec5..49695dd3677c 100644
> >> --- a/drivers/tty/serial/8250/8250_core.c
> >> +++ b/drivers/tty/serial/8250/8250_core.c
> >> @@ -555,6 +555,7 @@ static void __init serial8250_isa_init_ports(void)
> >> }
> >> }
> >>
> >> +#ifdef CONFIG_SERIAL_8250_ISA
> >
> > This is just making a mess of the code.
>
> It was already a mess.

True, but don't make it a worse one please.

>
> > To do this right, pull the isa code out into a separate file and put
> > the #ifdef in a .h file, so we can properly maintain and support this
> > code over time. This change as-is is not going to make that any
> > easier :(
>
> I might put in that effort if there's a reasonable chance this change
> will be accepted. If it's going to be rejected regardless, I'd rather
> not waste my time.
>
> >> +config SERIAL_8250_ISA
> >> + bool "8250/16550 ISA device support" if EXPERT
> >
> > So, no one will set this?
>
> I followed the pattern of the existing SERIAL_8250_PNP option. Was that
> a mistake? How would you prefer it?

I don't know, I'm just asking.

> > What userspace visable change will be caused by this?
>
> There won't be /dev/ttyS devices for ports that don't exist.
>
> > Will ports get renumbered?
>
> Not if they had predictable numbers to begin with.

So that would be "yes"? If so, obviously we couldn't take this, right?

thanks,
greg k-h

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