netdev - Re: [PATCH v1] ptp: add ToD device driver for Intel FPGA cards

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Date:   Tue, 14 Mar 2023 12:47:03 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Richard Cochran <richardcochran@...il.com>
Cc:     Tianfei Zhang <tianfei.zhang@...el.com>, netdev@...r.kernel.org,
        linux-fpga@...r.kernel.org, ilpo.jarvinen@...ux.intel.com,
        russell.h.weight@...el.com, matthew.gerlach@...ux.intel.com,
        pierre-louis.bossart@...ux.intel.com, vinicius.gomes@...el.com,
        Raghavendra Khadatare <raghavendrax.anand.khadatare@...el.com>
Subject: Re: [PATCH v1] ptp: add ToD device driver for Intel FPGA cards

On Mon, Mar 13, 2023 at 11:49:53AM -0700, Richard Cochran wrote:
> On Sun, Mar 12, 2023 at 11:02:39PM -0400, Tianfei Zhang wrote:

...

> > +	dt->ptp_clock = ptp_clock_register(&dt->ptp_clock_ops, dev);
> > +	if (IS_ERR(dt->ptp_clock))
> > +		return dev_err_probe(dt->dev, PTR_ERR(dt->ptp_clock),
> > +				     "Unable to register PTP clock\n");
> 
> Need to handle NULL as well...
> 
> /**
>  * ptp_clock_register() - register a PTP hardware clock driver
>  *
>  * @info:   Structure describing the new clock.
>  * @parent: Pointer to the parent device of the new clock.
>  *
>  * Returns a valid pointer on success or PTR_ERR on failure.  If PHC
>  * support is missing at the configuration level, this function
>  * returns NULL, and drivers are expected to gracefully handle that
>  * case separately.
>  */

I'm wondering why.

The semantics of the above is similar to gpiod_get_optional() and since NULL
is a valid return in such cases, the PTP has to handle this transparently to
the user. Otherwise it's badly designed API which has to be fixed.

TL;DR: If I'm mistaken, I would like to know why.

-- 
With Best Regards,
Andy Shevchenko