linux-kernel - Re: [PATCH v7] posix-timers: add clock

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Date: Wed, 03 Apr 2024 17:42:07 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: Mahesh Bandewar (महेश बंडेवार) <maheshb@...gle.com>
Cc: Sagi Maimon <maimon.sagi@...il.com>, richardcochran@...il.com,
 luto@...nel.org, mingo@...hat.com, bp@...en8.de,
 dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com, arnd@...db.de,
 geert@...ux-m68k.org, peterz@...radead.org, hannes@...xchg.org,
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 mark.rutland@....com, mszeredi@...hat.com, casey@...aufler-ca.com,
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 linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
 linux-arch@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH v7] posix-timers: add clock_compare system call

On Wed, Apr 03 2024 at 15:48, Thomas Gleixner wrote:
> On Tue, Apr 02 2024 at 16:37, Mahesh Bandewar (महेश बंडेवार) wrote:
> It is just an implementation detail whether you use a flag or a
> clockid. You can carry the clockid for the clocks which actually can be
> read in that context in a reserved field of PTP_SYS_OFFSET_EXTENDED:
>
> struct ptp_sys_offset_extended {
> 	unsigned int	n_samples; /* Desired number of measurements. */
> 	clockid_t	clockid;
> 	unsigned int	rsv[2];    /* Reserved for future use. */
> };
>
> and in the IOCTL:
>
>         if (extoff->clockid != CLOCK_MONOTONIC_RAW)
>         	return -EINVAL;

That should obviously be:

          switch (extoff->clockid) {
          case CLOCK_REALTIME:
          case CLOCK_MONOTONIC_RAW:
          	break;
          default:
                return -EINVAL;
          }
          
..

> 	sts.clockid = extoff->clockid;
>
> and it all just works, no?
>
> I have no problem to decide that PTP_SYS_OFFSET will not get this
> treatment and the drivers have to be converted over to
> PTP_SYS_OFFSET_EXTENDED.
>
> But adding yet another callback just to carry a clockid as argument is a
> more than pointless exercise as I demonstrated.
>
> Thanks,
>
>         tglx