[PATCH v1 02/14] serial: core: Add UPIO_UNSET constant for unset port type

[Florian Fainelli]

On 2/21/24 10:31, Andy Shevchenko wrote:
> In some APIs we would like to assign the special value to iotype
> and compare against it in another places. Introduce UPIO_UNSET
> for this purpose.
> 
> Note, we can't use 0, because it's a valid value for IO port access.
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko at linux.intel.com>
> ---
>   include/linux/serial_core.h | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
> index 2d2ec99eca93..2b0526ae1fac 100644
> --- a/include/linux/serial_core.h
> +++ b/include/linux/serial_core.h
> @@ -470,6 +470,7 @@ struct uart_port {
>   
>   	unsigned char		iotype;			/* io access style */
>   
> +#define UPIO_UNSET		((unsigned char)~0U)	/* UCHAR_MAX */

Nit: I would name this UPIO_UNKNOWN, or UPIO_NOTSET, unset means to me 
that it was previously set and we undid that action, whereas unknown or 
not set means we never did.
-- 
Florian