[LinuxPPS] http://lkml.org/lkml/2008/4/11/42

[Rodolfo Giometti]

On Sat, Apr 19, 2008 at 07:06:13PM +0200, Udo van den Heuvel wrote:
> Rodolfo Giometti wrote:
> >> Please comment.
> > 
> > I think we could do like this:
> > 
> > Step 1) Fix up the lowlevel x86-only irq method which improve
> >         resolution so much.
> 
> Sounds good to me.
> Maybe also make a small documentation (maybe even in the source) so
> other archs can be added easily.
> 
> > 	This step should be easy to implement regarding the timestamp
> > 	issue, a bit complicated regarding the echo function...
> 
> Care to explain?

Adding a timestamps recording it's easy due no locks required, but
implementing echo functions calls needs such locks.

> > Step 2) We can completely remove the PPS code from tty serial code
> > 	by using a "generic" client (maybe called pps-generic-irq?)
> > 	which can be used with any IRQ source.
> 
> How does that work with NMEA data from the same serial port?
> (I don't share a Gizmo2009 with my GPS's serial port but I'm just asking
> how I can maintain the current functionality)

If your serial port is connected with IRQ 4 you can load the module
as:

	$ modprobe modprobe pps-generic-irq.ko irqs=4

this will create a new PPS device which can be used to retreive
timestamps related with IRQ 4.

The serial code remains untouched. :)

> > 	We can implement something that loaded as follow:
> > 
> > 	$ modprobe pps-generic-irq.ko irqs=1,4
> 
> Or using kernel cmd-line parameter I hope?

Yes, or using whatever the kernel allows to use for automagic
configuration.

> > The first step should improve resolution and the second should remove
> > the problem with serial code.
> 
> Two steps forward?!
> What would Alan and the others think?

I never proposed these solution on LKML, I'd like before discuss with
you and try to implement some code before.

> > What do you think about these solutions? :)
> 
> Sound good to me.
> Maybe your complications can be solved somehow?

We should do some tests in order to find out if these steps can help.

Ciao,

Rodolfo

-- 

GNU/Linux Solutions                  e-mail:    giometti at enneenne.com
Linux Device Driver                             giometti at linux.it
Embedded Systems                     phone:	+39 349 2432127
UNIX programming                     skype:     rodolfo.giometti