linux-kernel - Re: [RFC 3/3] Documentation ABI: add PPS generators documentaion

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Message-ID: <2024100902-droop-uniformly-8dc8@gregkh>
Date: Wed, 9 Oct 2024 11:15:31 +0200
From: Greg KH <greg@...ah.com>
To: Rodolfo Giometti <giometti@...eenne.com>
Cc: linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>, corbet@....net,
	Hall Christopher S <christopher.s.hall@...el.com>,
	Mohan Subramanian <subramanian.mohan@...el.com>, tglx@...utronix.de,
	andriy.shevchenko@...ux.intel.com,
	Dong Eddie <eddie.dong@...el.com>, N Pandith <pandith.n@...el.com>,
	T R Thejesh Reddy <thejesh.reddy.t.r@...el.com>,
	Zage David <david.zage@...el.com>,
	Chinnadurai Srinivasan <srinivasan.chinnadurai@...el.com>
Subject: Re: [RFC 3/3] Documentation ABI: add PPS generators documentaion

On Wed, Oct 09, 2024 at 10:48:23AM +0200, Rodolfo Giometti wrote:
> On 08/10/24 17:43, Greg KH wrote:
> > On Tue, Oct 08, 2024 at 03:50:33PM +0200, Rodolfo Giometti wrote:
> > > This patch adds the documentation for the ABI between the Linux kernel
> > > and userspace regarding the PPS generators.
> > > 
> > > Signed-off-by: Rodolfo Giometti <giometti@...eenne.com>
> > > ---
> > >   Documentation/ABI/testing/sysfs-pps-gen | 44 +++++++++++++++++++++++++
> > >   1 file changed, 44 insertions(+)
> > >   create mode 100644 Documentation/ABI/testing/sysfs-pps-gen
> > > 
> > > diff --git a/Documentation/ABI/testing/sysfs-pps-gen b/Documentation/ABI/testing/sysfs-pps-gen
> > > new file mode 100644
> > > index 000000000000..9ad066cb3ce5
> > > --- /dev/null
> > > +++ b/Documentation/ABI/testing/sysfs-pps-gen
> > > @@ -0,0 +1,44 @@
> > > +What:		/sys/class/pps-gen/
> > > +Date:		October 2024
> > > +Contact:	Rodolfo Giometti <giometti@...eenne.com>
> > > +Description:
> > > +		The /sys/class/pps-gen/ directory will contain files and
> > > +		directories that will provide a unified interface to
> > > +		the PPS generators.
> > > +
> > > +What:		/sys/class/pps-gen/pps-genX/
> > > +Date:		October 2024
> > > +Contact:	Rodolfo Giometti <giometti@...eenne.com>
> > > +Description:
> > > +		The /sys/class/pps-gen/pps-genX/ directory is related to X-th
> > > +		PPS generator into the system. Each directory will
> > > +		contain files to manage and control its PPS generator.
> > > +
> > > +What:		/sys/class/pps-gen/pps-genX/enable
> > > +Date:		October 2024
> > > +Contact:	Rodolfo Giometti <giometti@...eenne.com>
> > > +Description:
> > > +		This write-only file enables or disables generation of the
> > > +		PPS signal.
> > > +
> > > +What:		/sys/class/pps-gen/pps-genX/name
> > > +Date:		October 2024
> > > +Contact:	Rodolfo Giometti <giometti@...eenne.com>
> > > +Description:
> > > +		This read-only file reports the name of the X-th generator.
> > 
> > Again, why a name?  What is that for?
> 
> This can be useful in order to distinguish between different PPS generators
> in the system.
> 
> For example, the PARPORT generator is not very precise, and userspace
> applications should be able to know which generator corresponds to the
> device /dev/pps-gen0 or /dev/pps-gen1, etc.

That's what the device symlink in the directory is for, no need to pick
yet-another-random-name to have to read from a file :)

thanks,

greg k-h