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

[Rodolfo Giometti]

On Fri, Apr 18, 2008 at 05:16:50PM +0200, Udo van den Heuvel wrote:
> 
> BTW: Besides the 'x86 lowlevel irq way' of obtaining timestamps (which
> works well), could we just duplicate the serial code to some extent and
> use that copy for the PPS stuff?
> This driver could be as minimal as we like.
> 
> (I doubt that idea will be accepted at the lkml...)
> 
> So what options do we have?
> 
> - Current approach
> - Lowlevel x86-only irq method (works best for resolution)
> - Copying the serial driver as I proposed above
> - Alan's ldisc idea (how much does it differ?)
> - ...
> 
> Please comment.

I think we could do like this:

Step 1) Fix up the lowlevel x86-only irq method which improve
        resolution so much.

	This step should be easy to implement regarding the timestamp
	issue, a bit complicated regarding the echo function...

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.

	We can implement something that loaded as follow:

	$ modprobe pps-generic-irq.ko irqs=1,4

	enables two PPS sources linked with IRQs 1 and 4.

The first step should improve resolution and the second should remove
the problem with serial code.

What do you think about these solutions? :)

Rodolfo

-- 

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