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Date: Tue, 21 Sep 2010 16:47:45 -0400 From: Kyle Moffett <kyle@...fetthome.net> To: John Stultz <johnstul@...ibm.com> Cc: Richard Cochran <richardcochran@...il.com>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org, devicetree-discuss@...ts.ozlabs.org, linux-arm-kernel@...ts.infradead.org, Krzysztof Halasa <khc@...waw.pl>, Rodolfo Giometti <giometti@...ux.it>, Arnd Bergmann <arnd@...db.de> Subject: Re: [PATCH 1/5] ptp: Added a brand new class driver for ptp clocks. On Fri, Aug 27, 2010 at 18:30, John Stultz <johnstul@...ibm.com> wrote: > On one side, there is the view that the kernel should abstract and hide > the hardware details to increase app portability. And the other is that > the raw hardware details should be exposed, so the OS stays out of the > way. > > Neither of these views are always right. Ideally we can come up with a > abstracted way to provide the hardware data needed that's generic enough > that applications don't have to be changed when moving between hardware > or configurations. > > The posix clock id interface is frustrating because the flat static > enumeration is really limiting. > > I wonder if a dynamic enumeration for posix clocks would be possibly a > way to go? Well how about something much more straightforward: #define CLOCK_FD 0x80000000 fd = open("/dev/clocks/some_clock_name", O_RDONLY); clock_gettime(CLOCK_FD | fd, &ts); This would provide all of the standard character-device semantics that everyone is accustomed to, and furthermore you could allow non-root users to manage specific clocks using just DAC permission bits. You'd still probably need to add a clock_adjtimex() syscall, but it could easily fail with EINVAL for software or per-thread clocks, but that seems like it would nicely abstract the hardware without forcing a numeric address space. Cheers, Kyle Moffett -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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