[LinuxPPS] multiple access to /dev/ppsN entries

[clemens at dwf.com]

> Hello all,
> 
> I am in the midst of designing a timing subsystem for a linux based project.
> I think that the LinuxPPS project is a very useful addition to the kernel
> and I would like to incorporate it into this design. First, my thanks to you
> for creating and especially pushing this code upstream.
> 
> I _think_ that I need to have multiple processes accessing the same
> /dev/ppsN entry -- I'm hoping that you will offer your expert opinion as to
> whether this is possible.
> 
> It looks like the pps_cdev_open() in 2.6.33 (
> http://lxr.linux.no/#linux+v2.6.33/drivers/pps/pps.c#L197 ) is not
> implementing any access control and that the 'atomic_t usage' member of
> pps_device ( http://lxr.linux.no/linux+*/include/linux/pps_kernel.h#L65 ) is
> there to facilitate ref counting so that there can be multiple opens of
> /dev/pps device nodes.
> 
I have run both ntp and my test program at the same time, so there is
no problem with two separate programs opening /dev/pps0
-- 
                                        Reg.Clemens
                                        reg at dwf.com