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Date: Thu, 19 Aug 2010 08:23:01 -0700 From: "Ira W. Snyder" <iws@...o.caltech.edu> To: Arnd Bergmann <arnd@...db.de> Cc: Richard Cochran <richardcochran@...il.com>, Rodolfo Giometti <giometti@...ux.it>, john stultz <johnstul@...ibm.com>, devicetree-discuss@...ts.ozlabs.org, linux-kernel@...r.kernel.org, netdev@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org, linux-arm-kernel@...ts.infradead.org, Krzysztof Halasa <khc@...waw.pl> Subject: Re: [PATCH 1/5] ptp: Added a brand new class driver for ptp clocks. On Thu, Aug 19, 2010 at 02:29:49PM +0200, Arnd Bergmann wrote: > On Thursday 19 August 2010, Richard Cochran wrote: > > > > On Wed, Aug 18, 2010 at 05:02:03PM +0200, Arnd Bergmann wrote: > > > You might want to use callbacks for these system calls that you > > > can register to at module load time, like it is done for the > > > existing syscalls. > > > > Can you point me to a specific example? > > The struct k_clock contains callback functions to clock source > specific implementations of the syscalls and other functions. > Adding a new clock source that is (potentially) implemented > as a module means you have to define a new k_clock in that module > that you register using register_posix_clock. > > If you need additional syscalls to be implemented by the same > module, you can put more callback functions into struct k_clock > that would then only be implemented by the new module. > > > > The simpler way (e.g. for testing) is using Kconfig dependencies, like > > > > > > config PTP > > > bool "IEEE 1588 Precision Time Protocol" > > > > > > config PPS > > > tristate "Pulse per Second" > > > depends on PTP || !PTP > > > > > > The depends statement is a way of expressing that when PTP is enabled, > > > PPS cannot be a module, while it may be a module if PTP is disabled. > > > > THis did not work for me. > > > > What I got was, in effect, two independent booleans. > > Hmm, right. I wonder what I was thinking of then. > > You can certainly do > > config PTP > bool "IEEE 1588 Precision Time Protocol" > depends on PPS != m > > but that will hide the PTP option if PPS is set to 'm', which is normally > not what you want. > Arnd, Perhaps you were thinking of the vhost example (taken from drivers/vhost/Kconfig): config VHOST_NET tristate "Host kernel accelerator for virtio net (EXPERIMENTAL)" depends on NET && EVENTFD && (TUN || !TUN) && (MACVTAP || !MACVTAP) && EXPERIMENTAL They have a similar construct with both TUN and MACVTAP there. Perhaps the parens are a necessary part of the "X || !X" syntax? Just a random guess. Ira -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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