[LinuxPPS] [PATCH 01/11] PPS: Don't waste time getting unnecessary timestamps.

[Rodolfo Giometti]

On Fri, Feb 06, 2009 at 08:25:38AM -0500, George Spelvin wrote:
> Here is a patch series for cleaning up linuxpps 5.3.4.
> 
> ---
>  drivers/pps/clients/pps-ldisc.c |   16 ++++++----------
>  1 files changed, 6 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/pps/clients/pps-ldisc.c b/drivers/pps/clients/pps-ldisc.c
> index f16396b..0406f40 100644
> --- a/drivers/pps/clients/pps-ldisc.c
> +++ b/drivers/pps/clients/pps-ldisc.c
> @@ -33,17 +33,13 @@ static void pps_tty_dcd_change(struct tty_struct *tty, unsigned int status,
>  	struct timespec __ts;
>  	struct pps_ktime pps_ts;
>  
> -	/* First of all we get the time stamp... */
> -	getnstimeofday(&__ts);
> -
> -	/* Does caller give us a timestamp? */
> -	if (ts) {	/* Yes. Let's use it! */
> -		pps_ts.sec = ts->tv_sec;
> -		pps_ts.nsec = ts->tv_nsec;
> -	} else {	/* No. Do it ourself! */
> -		pps_ts.sec = __ts.tv_sec;
> -		pps_ts.nsec = __ts.tv_nsec;
> +	/* Get timestamp if necessary */
> +	if (!ts) {
> +		getnstimeofday(&__ts);
> +		ts = &__ts;
>  	}
> +	pps_ts.sec = ts->tv_sec;
> +	pps_ts.nsec = ts->tv_nsec;

Nack.

Function getnstimeofday() should be called as soon as possible since
even a little delay may cause a large timing error! So is better
calling getnstimeofday() even if not necessary then delay it.

Ciao,

Rodolfo

-- 

GNU/Linux Solutions                  e-mail: giometti at enneenne.com
Linux Device Driver                          giometti at linux.it
Embedded Systems                     phone:  +39 349 2432127
UNIX programming                     skype:  rodolfo.giometti