linux-kernel - Re: [PATCH 3/4] iio: backend: make use of dev_errp

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Date: Thu, 4 Apr 2024 18:12:25 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Nuno Sá <noname.nuno@...il.com>
Cc: Nuno Sa <nuno.sa@...log.com>, Petr Mladek <pmladek@...e.com>,
	Jonathan Cameron <jic23@...nel.org>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Olivier Moysan <olivier.moysan@...s.st.com>,
	Jyoti Bhayana <jbhayana@...gle.com>,
	Chris Down <chris@...isdown.name>,
	John Ogness <john.ogness@...utronix.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org
Subject: Re: [PATCH 3/4] iio: backend: make use of dev_errp_probe()

On Thu, Apr 04, 2024 at 04:58:27PM +0200, Nuno Sá wrote:
> On Thu, 2024-04-04 at 15:23 +0300, Andy Shevchenko wrote:
> > On Thu, Apr 04, 2024 at 01:06:25PM +0200, Nuno Sa wrote:
> > > Using dev_errp_probe() to simplify the code.

..

> > > +	if (IS_ERR(fwnode))
> > > +		return dev_errp_probe(dev, PTR_ERR(fwnode),
> > > +				      "Cannot get Firmware reference\n");
> > 
> > ERR_CAST() seems quite good candidate to have here.
> > 
> > 		return dev_errp_probe(dev, fwnode, "Cannot get Firmware
> > reference\n");
> > 
> > (Assuming dev_errp_probe() magically understands that, note you may have it as
> >  a macro and distinguish parameter type with _Generic() or so and behave
> >  differently: ERR_PTR() vs. ERR_CAST(), see acpi_dev_hid_uid_match()
> >  implementation, but also keep in mind that it doesn't distinguish NULL/0,
> > there
> >  is a patch available in the mailing list to fix that, though.)
> 
> Do we care that much for going with that trouble?

I don't think we do. We are not supposed to be called with ret == 0/NULL.
That's why I pointed out to the current version.

> I understand like this we go
> PTR_ERR() to then comeback to ERR_PTR() but this for probe() which is not a
> fastpath. So perhaps we could just keep it simple?

It's not about performance, it's about readability. See the difference between
yours and mine.

-- 
With Best Regards,
Andy Shevchenko