Re: [Bug 212265] New: clock_gettime(CLOCK_TAI, ...) should return an error when TAI has not been configured

[Richard Cochran <richardcochran@gmail.com>]

On Mon, Mar 29, 2021 at 04:57:55PM +0200, Thomas Gleixner wrote:
> I think adjtimex is the right place and not yet another random file
> somewhere. Something like the below.

Perfect.

Acked-by: Richard Cochran <richardcochran@gmail.com>

> ---
>  include/uapi/linux/timex.h |    7 +++++--
>  kernel/time/ntp.c          |    4 +++-
>  2 files changed, 8 insertions(+), 3 deletions(-)
> 
> --- a/include/uapi/linux/timex.h
> +++ b/include/uapi/linux/timex.h
> @@ -188,9 +188,12 @@ struct __kernel_timex {
>  #define STA_MODE	0x4000	/* mode (0 = PLL, 1 = FLL) (ro) */
>  #define STA_CLK		0x8000	/* clock source (0 = A, 1 = B) (ro) */
>  
> +#define STA_TAISET	0x10000 /* TAI offset was set via adjtimex (ro) */
> +
>  /* read-only bits */
> -#define STA_RONLY (STA_PPSSIGNAL | STA_PPSJITTER | STA_PPSWANDER | \
> -	STA_PPSERROR | STA_CLOCKERR | STA_NANO | STA_MODE | STA_CLK)
> +#define STA_RONLY (STA_PPSSIGNAL | STA_PPSJITTER | STA_PPSWANDER |	\
> +		   STA_PPSERROR | STA_CLOCKERR | STA_NANO | STA_MODE |	\
> +		   STA_CLK | STA_TAISET)
>  
>  /*
>   * Clock states (time_state)
> --- a/kernel/time/ntp.c
> +++ b/kernel/time/ntp.c
> @@ -741,8 +741,10 @@ static inline void process_adjtimex_mode
>  	}
>  
>  	if (txc->modes & ADJ_TAI &&
> -			txc->constant >= 0 && txc->constant <= MAX_TAI_OFFSET)
> +	    txc->constant >= 0 && txc->constant <= MAX_TAI_OFFSET) {
>  		*time_tai = txc->constant;
> +		time_status |= STA_TAISET;
> +	}
>  
>  	if (txc->modes & ADJ_OFFSET)
>  		ntp_update_offset(txc->offset);