Re: [PATCH v2 2/4] serial: 8250_dw: Only accept a contiguous DLF readback

[Jiri Slaby]

On 19. 10. 26, 22:06, Vinicius Pedrosa wrote:
> --- a/drivers/tty/serial/8250/8250_dwlib.c
> +++ b/drivers/tty/serial/8250/8250_dwlib.c
> @@ -225,7 +225,11 @@ void dw8250_setup_port(struct uart_port *p)
>   	reg = dw8250_readl_ext(p, DW_UART_DLF);
>   	dw8250_writel_ext(p, DW_UART_DLF, old_dlf);
>   
> -	if (reg) {
> +	/*
> +	 * DLF is a bit field starting at bit 0, so a real one reads back as
> +	 * 2^n - 1. Any other value means this offset is something else.
> +	 */
> +	if (reg && !(reg & (reg + 1))) {

Do I understand correctly, that this equivalent to:
  if (is_power_of_2(reg + 1))
?

thanks,
--
js
suse labs