Re: [PATCH v2 0/2] make POSIX timers optional

On Tue, 20 Sep 2016, Thomas Gleixner wrote:

I think the whole approach is wrong because it makes the PTP split at the
wrong level.

Currently we have:

	  DRIVER_X
	  tristate "Driver X"
	  select PTP

In order to make POSIX_CLOCK configurable we should have

       	  PTP
	  tristate "PTP"
	  select POSIX_CLOCK

Now if you want to distangle PTP from a driver then you split it at the
driver level and not at the PTP level:

      	  DRIVER_X
	  tristate "Driver X"

	  DRIVER_X_PTP
	  bool "Enable PTP support"
	  default y if !MAKE_IT_TINY
	  depends on DRIVER_X
	  select PTP

We have already drivers following that scheme. That way you make the PTP
support in the driver conditional on DRIVER_X_PTP and have no hassle with
modules and dependencies.

I beg to disagree.

There are way more drivers than subsystems and if you had to go around 
unselecting all NIC drivers for CONFIG_ETHERNET to be turned off, and 
with CONFIG_ETHERNET=n you'd finally be able to turn networking off, 
then this would be a nightmare.

IMHO it is much nicer for the poor user configuring the kernel to have a 
single configuration prompt for PTP support, and then have whatever 
driver that can provide a PTP clock just do it (or omit it) based on 
that single prompt.  Prompting for PTP support for each individual 
ethernet driver is silly.


Nicolas