linux-kernel - Re: [Intel PMC TGPIO Driver 3/5] drivers/ptp: Add user-space input polling interface

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Message-ID: <20200203022850.GC3516@localhost>
Date:   Sun, 2 Feb 2020 18:28:50 -0800
From:   Richard Cochran <richardcochran@...il.com>
To:     christopher.s.hall@...el.com
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        tglx@...utronix.de, hpa@...or.com, mingo@...hat.com,
        x86@...nel.org, jacob.e.keller@...el.com, davem@...emloft.net,
        sean.v.kelley@...el.com
Subject: Re: [Intel PMC TGPIO Driver 3/5] drivers/ptp: Add user-space input
 polling interface

On Wed, Dec 11, 2019 at 01:48:50PM -0800, christopher.s.hall@...el.com wrote:
> From: Christopher Hall <christopher.s.hall@...el.com>
> 
> The Intel PMC Time-Aware GPIO controller doesn't implement interrupts to
> notify software that an input event has occurred. To solve this problem,
> implement a user-space polling interface allowing the application to check
> for input events. The API returns an event count and time. This interface
> (EVENT_COUNT_TSTAMP2) is *reused* from the output frequency adjustment API.
> The event count delta indicates that one or more events have occurred and
> how many events may have been missed.

So I think this interface is truly horrible.  

The ptp_pin_desc describes a pin's configuration WRT the PTP_PF_xxx
and the specific EXTTS/PEROUT_REQUEST channel.  I don't know exactly
what you are trying to accomplish, but there has got to be a better
way.  Re-using the ptp_pin_desc for a polling interface is surely not
the way forward.

Thanks,
Richard