linux-kernel - Re: [PATCH v2 7/9] serial: st-asc: Sanitize CSIZE and correct PARENB for CS7

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Date:   Fri, 20 May 2022 08:19:36 +0200
From:   Patrice CHOTARD <patrice.chotard@...s.st.com>
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        <linux-serial@...r.kernel.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Shubhrajyoti Datta <shubhrajyoti.datta@...il.com>,
        Srinivas Kandagatla <srinivas.kandagatla@...com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 7/9] serial: st-asc: Sanitize CSIZE and correct PARENB
 for CS7

Hi Ilpo

On 5/19/22 10:18, Ilpo Järvinen wrote:
> Only CS7 and CS8 seem supported but CSIZE is not sanitized from CS5 or
> CS6 to CS8. In addition, ASC_CTL_MODE_7BIT_PAR suggests that CS7 has
> to have parity, thus add PARENB.
> 
> Incorrect CSIZE results in miscalculation of the frame bits in
> tty_get_char_size() or in its predecessor where the roughly the same
> code is directly within uart_update_timeout().
> 
> Cc: Srinivas Kandagatla <srinivas.kandagatla@...com>
> Fixes: c4b058560762 (serial:st-asc: Add ST ASC driver.)
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> ---
>  drivers/tty/serial/st-asc.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/tty/serial/st-asc.c b/drivers/tty/serial/st-asc.c
> index d7fd692286cf..1b0da603ab54 100644
> --- a/drivers/tty/serial/st-asc.c
> +++ b/drivers/tty/serial/st-asc.c
> @@ -535,10 +535,14 @@ static void asc_set_termios(struct uart_port *port, struct ktermios *termios,
>  	/* set character length */
>  	if ((cflag & CSIZE) == CS7) {
>  		ctrl_val |= ASC_CTL_MODE_7BIT_PAR;
> +		cflag |= PARENB;
>  	} else {
>  		ctrl_val |= (cflag & PARENB) ?  ASC_CTL_MODE_8BIT_PAR :
>  						ASC_CTL_MODE_8BIT;
> +		cflag &= ~CSIZE;
> +		cflag |= CS8;
>  	}
> +	termios->c_cflag = cflag;
>  
>  	/* set stop bit */
>  	ctrl_val |= (cflag & CSTOPB) ? ASC_CTL_STOP_2BIT : ASC_CTL_STOP_1BIT;

Reviewed-by: Patrice Chotard <patrice.chotard@...s.st.com>

Thanks
Patrice