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 _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev