RE: Intel timed i/o driver in HTE

[N, Pandith]

> -----Original Message-----
> From: Dipen Patel <dipenp@xxxxxxxxxx>
> Sent: Wednesday, November 30, 2022 8:54 AM
> To: Linus Walleij <linus.walleij@xxxxxxxxxx>; N, Pandith
> <pandith.n@xxxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx; Hall, Christopher S
> <christopher.s.hall@xxxxxxxxx>; Gross, Mark <mark.gross@xxxxxxxxx>;
> Sangannavar, Mallikarjunappa <mallikarjunappa.sangannavar@xxxxxxxxx>;
> D, Lakshmi Sowjanya <lakshmi.sowjanya.d@xxxxxxxxx>; T R, Thejesh Reddy
> <thejesh.reddy.t.r@xxxxxxxxx>; andriy.shevchenko@xxxxxxxxxxxxxxx;
> timestamp@xxxxxxxxxxxxxxx
> Subject: Re: Intel timed i/o driver in HTE
> 
> On 11/23/22 1:22 PM, Linus Walleij wrote:
> > On Wed, Nov 23, 2022 at 3:38 PM N, Pandith <pandith.n@xxxxxxxxx>
> wrote:
> >
> >> Since the current gpio framework is inadequate to periodic output
> modes.
> >> I thought to disentangle from gpio and develop a new hte consumer.
> >> Something like hte-libcdev.c
> >
> > Maybe, if Dipen wants it.
> > Or maybe it needs its own subsystem.
> > Or maybe it should be with whatever is using these pulse trains.
> >
> Few things I want to know from Pandith as below:
> 1. Does timed io only meant for GPIO or other signals? if other signals, what
> type of signals?
This could be time sync signals or periodic/single pulse input for timestamp support
 
> 2. In the output mode case where for example, timed io IP outputs 1ms GPIO
> pulse, does it also timestamp it for consumers to retrieve later?
No. In output mode, either single shot or periodic pulse train is generated.
But timed i/o does keep timestamp data in input mode.

> 3. Can you share rough idea you have in mind for the hte-libcdev?
a. This layer can provide ioctl based user interactions for timestamp services (input and output mode)
b. char device creation for timestamping hardware. Something like /dev/hteX 
c.  Develop a native hte consumer, which handles user space interactions of hte subsystem
> 
> > Again: what is it used for? If we have no idea what it is supposed to
> > be used for, we cannot place it right, even less test it.
> I think it can possibly act as time sync server as one of the use case.
> >
> > Yours,
> > Linus Walleij