Re: [PATCH] serial: 8250: don't register ports that have no hardware

[Jiri Slaby <jirislaby@kernel.org>]

On 18. 08. 26, 20:52, Lucas Tanure wrote:
> The 8250 driver creates a fixed set of port slots at boot and
> registers a ttyS device for each one, even when the slot describes no
> hardware. On device tree platforms those slots are empty, but they
> still take the ttyS0..ttyS3 names.
> 
> New Amlogic SoCs (S4, T7) name their real UARTs ttyS as well. With
> both drivers built in, as in arm64 defconfig, the real port fails to bind:
> 
>    sysfs: cannot create duplicate filename '/class/tty/ttyS0'
>    meson_uart fe078000.serial: Cannot register tty device on line 0
> 
> Skip slots that have no I/O and no memory address. Legacy x86 slots
> come with resources and are not affected.
> 
> Signed-off-by: Lucas Tanure <tanure@linux.com>
> Assisted-by: Claude:claude-fable-5
> ---
>   drivers/tty/serial/8250/8250_core.c | 8 ++++++++
>   1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
> index f49862d90eeb..e66e0cdbb210 100644
> --- a/drivers/tty/serial/8250/8250_core.c
> +++ b/drivers/tty/serial/8250/8250_core.c
> @@ -378,6 +378,14 @@ void __init serial8250_register_ports(struct uart_driver *drv, struct device *de
>   		if (up->port.dev)
>   			continue;
>   
> +		/*
> +		 * Skip slots that describe no hardware: they would only
> +		 * take up ttyS<n> names. Real ports get their node when
> +		 * they claim a slot in serial8250_register_8250_port().
> +		 */
> +		if (!up->port.iobase && !up->port.mapbase && !up->port.membase)
> +			continue;

So you can no longer set up those ports via TIOCSSERIAL?

And what about already registered consoles?

Why does meson register ttyS* in the first place?

F*ck AI proposed changes.

thanks,
-- 
js
suse labs