Messages in this thread | | | Date | Tue, 17 Aug 2010 10:32:16 +0200 | From | Richard Cochran <> | Subject | Re: [PATCH 1/5] ptp: Added a brand new class driver for ptp clocks. |
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On Mon, Aug 16, 2010 at 09:59:39PM +0200, Arnd Bergmann wrote: > Why does it matter how long it takes to read the clock? I wasn't thinking > of replacing the system clock with this, just exposing the additional > clock as a new clockid_t value that can be accessed using the existing > syscalls.
Okay, now I see. You are suggesting this:
clock_gettime(CLOCK_PTP, &ts); clock_settime(CLOCK_PTP, &ts);
I like this. If there is agreement about it, I am happy to implement the PTP stuff that way.
> Why did you not want to add syscalls? Adding ioctls instead of syscalls > does not make the interface better, just less visible.
I bet that, had I posted patch set with new syscalls, someone would have said, "You are adding new syscalls. Can't you just use a char device instead!"
If you add syscalls and introduce CLOCK_PTP, then you add it to everyone's kernel, even those people who never heard of PTP. A char device has the advantage that can it be simply ignored. Also, a syscall has got to have the right form from the very beginning. If the next generation of PTP hardware looks very different, then it is not that much of a crime to change an ioctl interface, provided it has versioning.
Richard
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