Re: [PATCH v6 2/8] serial: 8250: share the RX trigger conversion helper

[Andy Shevchenko]

On Mon, Nov 02, 2026 at 12:55:17PM -0700, James Hilliard wrote:
> Drivers can supply receive-trigger thresholds through the RX trigger
> callbacks without adding a legacy port type to uart_config[]. Extract the
> threshold search into serial8250_bytes_to_fcr() so those drivers can use
> the same conversion as the generic 8250 implementation.
> 
> Keep the implementation in 8250_port.c and export it in the SERIAL_8250
> namespace. Include the unsupported-table check and preserve the existing
> nearest-lower selection and highest-encoding fallback.

...

> -static int bytes_to_fcr_rxtrig(struct uart_8250_port *up, unsigned char bytes)
> +int serial8250_bytes_to_fcr(const unsigned char *rxtrig_bytes, unsigned char bytes)
>  {
> -	const struct serial8250_config *conf_type = &uart_config[up->port.type];
> -	int i;
> -
> -	if (!conf_type->rxtrig_bytes[UART_FCR_R_TRIG_BITS(UART_FCR_R_TRIG_00)])
> +	if (!rxtrig_bytes[UART_FCR_R_TRIG_BITS(UART_FCR_R_TRIG_00)])
>  		return -EOPNOTSUPP;
>  
> -	for (i = 1; i < UART_FCR_R_TRIG_MAX_STATE; i++) {
> -		if (bytes < conf_type->rxtrig_bytes[i])
> +	for (unsigned int i = 1; i < UART_FCR_R_TRIG_MAX_STATE; i++) {
> +		if (bytes < rxtrig_bytes[i])
>  			/* Use the nearest lower value */
> -			return (--i) << UART_FCR_R_TRIG_SHIFT;
> +			return (i - 1) << UART_FCR_R_TRIG_SHIFT;
>  	}

Strictly speaking cosmetics should go into a separate patch (for-loop iterator
locality, (--i) morph).

>  	return UART_FCR_R_TRIG_11;
>  }

-- 
With Best Regards,
Andy Shevchenko