linux-kernel - Re: [PATCH 3/3] serial: core: Update uart_poll

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Date:   Mon, 16 Oct 2023 14:44:32 +0300 (EEST)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     Vamshi Gajjela <vamshigajjela@...gle.com>
cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        ilpo.jarvinen@...ux.intel.com, linux-serial@...r.kernel.org,
        linux-kernel@...r.kernel.org, manugautam@...gle.com,
        Subhash Jadavani <sjadavani@...gle.com>,
        Channa Kadabi <kadabi@...gle.com>
Subject: Re: [PATCH 3/3] serial: core: Update uart_poll_timeout function to
 return unsigned int

On Sat, 14 Oct 2023, Vamshi Gajjela wrote:

> From: VAMSHI GAJJELA <vamshigajjela@...gle.com>
> 
> uart_fifo_timeout() returns unsigned value, hence the function
> uart_poll_timeout has been modified to use an unsigned int type for
> timeout values instead of a signed int. The return type of the function
> has been changed from int to unsigned int for consistency with the type
> of timeout values. The result of uart_fifo_timeout() is cast to u32,
> indicating that the value is truncated.
> 
> Signed-off-by: VAMSHI GAJJELA <vamshigajjela@...gle.com>
> ---
>  include/linux/serial_core.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
> index b128513b009a..445a1ff7e502 100644
> --- a/include/linux/serial_core.h
> +++ b/include/linux/serial_core.h
> @@ -773,9 +773,9 @@ static inline unsigned long uart_fifo_timeout(struct uart_port *port)
>  }
>  
>  /* Base timer interval for polling */
> -static inline int uart_poll_timeout(struct uart_port *port)
> +static inline unsigned int uart_poll_timeout(struct uart_port *port)

This is in jiffies so why don't you return unsigned long instead also 
here?

>  {
> -	int timeout = uart_fifo_timeout(port);
> +	unsigned int timeout = (u32)uart_fifo_timeout(port);

Use unsigned long and avoid casting entirely?
>  
>  	return timeout > 6 ? (timeout / 2 - 2) : 1;
>  }
> 

-- 
 i.