quote on Fri, Jul 01, 2016 at 05:18:17PM +0200 (Richard Cochran):
> On Fri, Jul 01, 2016 at 01:43:43PM +0300, Ivan Oleynikov wrote:
> > This is simply icquired by using `realpath(3)` of value passed with -p
> > parameter instead of its original value.
>
> Can you please explain what problem this patch fixes?
Imagine i have a symlink to my /dev/ptp0:
ln -s /dev/ptp0 /dev/my_ptp
If i try to syncronize that PHC over the network interface gbe0 i get:
# ptp4l -p /dev/my_ptp -i gbe0 -m -s
ptp4l[2117.975]: bad ptp device string
failed to create a clock
It seems strange that ptp4l expects path to ptp device to be in the form
"/dev/ptp%d". This also forbids me to specify a relative path to PHC
device. E.g:
# ptp4l -p /dev/../dev/ptp0 -i gbe0 -m -s
ptp4l[2268.015]: bad ptp device string
failed to create a clock
Working with PHC through a symlink instead of directly passing /dev/ptp0 to
`ptl4l -p` can be useful when you have multiple PTP clocks in your system and
the order in which they are registered is unpredictable (as well as name of your
desired PHC file in /dev/). So you have to look at
/sys/class/ptp/ptp*/{clock_name, device} to find the name of your device.
Alternative solution would be to create udev rule matching ptp device with
specific DRIVERS, KERNELS, etc. that will add a symlink (e.g. /dev/my_ptp in the
first example) to your device.
This patch makes ptp4l find full path to PHC using `realpath(3)` before doing
anything else with it. Thus allowing me to:
# ptp4l -p /dev/../dev/ptp0 -i gbe0 -m -s
ptp4l[5346.225]: selected /dev/ptp0 as PTP clock
And also to:
# ptp4l -p /dev/my_ptp -i gbe0 -m -s
ptp4l[5368.645]: selected /dev/ptp0 as PTP clock
Better solution would be to determine phc_index by given PHC char device path
without parsing its path (maybe by looking at sysfs or by some ioctl), but I
couldn't find a way to do that. This would allow me to create char device with
arbitrary name for my PHC (with mknod or by renaming it in udev).
--
Ivan Oleynikov
STC Metrotek
St.Petersburg
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