linux-kernel - Re: [Intel PMC TGPIO Driver 2/5] drivers/ptp: Add PEROUT2 ioctl frequency adjustment interface

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Message-ID: <20200226002026.GB32079@skl-build>
Date:   Tue, 25 Feb 2020 16:20:26 -0800
From:   "Christopher S. Hall" <christopher.s.hall@...el.com>
To:     Richard Cochran <richardcochran@...il.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 2/5] drivers/ptp: Add PEROUT2 ioctl
 frequency adjustment interface

Hi Richard,

On Sun, Feb 02, 2020 at 06:14:29PM -0800, Richard Cochran wrote:
> On Wed, Dec 11, 2019 at 01:48:49PM -0800, christopher.s.hall@...el.com wrote:
> > diff --git a/include/linux/ptp_clock_kernel.h b/include/linux/ptp_clock_kernel.h

> > +	int (*counttstamp)(struct ptp_clock_info *ptp,
> > +			   struct ptp_event_count_tstamp *count);
> 
> KernelDoc missing.

> As tglx said, it is hard to guess what this will be used for.  I would
> appreciate a fuller explanation of the new callback in the commit log
> message.

Yes, to both of these above. More incremental patches as you point out
below also helps here. I have replied to tglx and you in another thread.

> In general, please introduce a specific new API with an example of how
> it is used.  In this series you have three new APIs,
> 
>    [Intel PMC TGPIO Driver 2/5] drivers/ptp: Add PEROUT2 ioctl frequency adjustment interface
>    [Intel PMC TGPIO Driver 3/5] drivers/ptp: Add user-space input polling interface
>    [Intel PMC TGPIO Driver 4/5] x86/tsc: Add TSC support functions to support ART driven Time-Aware GPIO
> 
> and then a largish driver using them all.
> 
>    [Intel PMC TGPIO Driver 5/5] drivers/ptp: Add PMC Time-Aware GPIO Driver
> 
> May I suggest an ordering more like:
> 
> [1/5] x86/tsc: Add TSC support functions to support ART...	(with forward explanation of the use case)
> [2/5] drivers/ptp: Add PMC Time-Aware GPIO Driver		(without new bits)
> [3/5] drivers/ptp: Add Enhanced handling of reserve fields	(okay as is)
> [4/5] drivers/ptp: Add PEROUT2 ioctl frequency adjustment interface
> [5/5] implement ^^^ in the driver
> [6/5] drivers/ptp: Add user-space input polling interface
> [7/5] implement ^^^ in the driver

This makes sense. Thanks for the detail here.

> > @@ -164,10 +179,14 @@ struct ptp_pin_desc {
> >  	 * PTP_EXTTS_REQUEST and PTP_PEROUT_REQUEST ioctls.
> >  	 */
> >  	unsigned int chan;
> > +	/*
> > +	 * Per pin capability flag
> > +	 */
> > +	unsigned int flags;
> 
> Please use 'capabilities' instead of 'flags'.

Yes. Makes sense.

> Thanks,
> Richard

Thanks,
Christopher