linux-kernel - RE: [PATCH v6 2/4] iio: adc: Add Xilinx AMS driver

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Date:   Mon, 19 Jul 2021 07:49:35 +0000
From:   Anand Ashok Dumbre <ANANDASH@...inx.com>
To:     Jonathan Cameron <Jonathan.Cameron@...wei.com>
CC:     Jonathan Cameron <jic23@...nel.org>,
        "lars@...afoo.de" <lars@...afoo.de>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        Michal Simek <michals@...inx.com>,
        "pmeerw@...erw.net" <pmeerw@...erw.net>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Manish Narani <MNARANI@...inx.com>, git <git@...inx.com>
Subject: RE: [PATCH v6 2/4] iio: adc: Add Xilinx AMS driver



> -----Original Message-----
> From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> Sent: Thursday 15 July 2021 1:52 PM
> To: Anand Ashok Dumbre <ANANDASH@...inx.com>
> Cc: Jonathan Cameron <jic23@...nel.org>; lars@...afoo.de; linux-
> iio@...r.kernel.org; git-dev <git-dev@...inx.com>; Michal Simek
> <michals@...inx.com>; pmeerw@...erw.net; devicetree@...r.kernel.org;
> linux-kernel@...r.kernel.org; Manish Narani <MNARANI@...inx.com>
> Subject: Re: [PATCH v6 2/4] iio: adc: Add Xilinx AMS driver
> 
> ...
> 
> > >
> > > > +	if (IS_ERR(ams->base))
> > > > +		return PTR_ERR(ams->base);
> > > > +
> > > > +	ams->clk = devm_clk_get(&pdev->dev, NULL);
> > > > +	if (IS_ERR(ams->clk))
> > > > +		return PTR_ERR(ams->clk);
> > > > +	clk_prepare_enable(ams->clk);
> > > > +	devm_add_action_or_reset(&pdev->dev, (void
> > > *)clk_disable_unprepare,
> > > > +				 ams->clk);
> > > > +
> > > > +	INIT_DELAYED_WORK(&ams->ams_unmask_work,
> > > ams_unmask_worker);
> > > > +	devm_add_action_or_reset(&pdev->dev, (void
> > > *)cancel_delayed_work,
> > >
> > > I'm not keen on casting away the function pointer type.  Normally
> > > we'd just wrap it in a local function, to make it clear it was
> > > deliberate and avoid potential nasty problems if the signature of the
> function ever changes.
> > >
> > > It's 3 lines of boilerplate, but will give me warm fuzzy feelings!
> > > Same for the other case above.  The fact this isn't done in exising
> > > kernel code make this particularly risky.
> >
> > Makes sense. I will revert the code back to its original and handle
> > the cases using goto and inside remove()
> Ah.  Not what I meant.  I was suggesting you add a little function locally that
> has the right type and in turn calls cancel_delayed_work().
> 
> As that directly exposes the actual function calls, any signature change in
> future will cause compile breakage (or be picked up any automated tools
> doing that refactor).

Now I understand.
Will fix it in the next series.

> 
> >
> > >
> > > > +				 &ams->ams_unmask_work);
> > > > +
> > > > +	ret = ams_init_device(ams);
> > > > +	if (ret) {
> > > > +		dev_err(&pdev->dev, "failed to initialize AMS\n");
> > > > +		return ret;
> > > > +	}
> > > > +
> > > > +	ret = ams_parse_dt(indio_dev, pdev);
> > > > +	if (ret) {
> > > > +		dev_err(&pdev->dev, "failure in parsing DT\n");
> > > > +		return ret;
> > > > +	}
> > > > +
> > > > +	ams_enable_channel_sequence(indio_dev);
> > > > +
> > > > +	ams->irq = platform_get_irq(pdev, 0);
> > >
> > > platform_get_irq () can return errors, in particular -EPROBE_DEFER
> > > so I'd check that and return before you call devm_request_irq() I'm
> > > not sure
> > > devm_request_irq() will not eat that error code.
> > >
> >
> > Will fix this in next series.
> >
> > >
> > > > +	ret = devm_request_irq(&pdev->dev, ams->irq, &ams_irq, 0, "ams-
> > > irq",
> > > > +			       indio_dev);
> > > > +	if (ret < 0) {
> > > > +		dev_err(&pdev->dev, "failed to register interrupt\n");
> > > > +		return ret;
> > > > +	}
> > > > +
> > > > +	platform_set_drvdata(pdev, indio_dev);
> > > > +
> > > > +	return iio_device_register(indio_dev); }
> > > > +
> > > > +static int ams_remove(struct platform_device *pdev) {
> > > > +	struct iio_dev *indio_dev = platform_get_drvdata(pdev);
> > > > +
> > > > +	iio_device_unregister(indio_dev);
> > >
> > > If this is all you have in remove, then you can use
> > > devm_iio_device_register() in probe() and not need an remove() callback
> at all.
> >
> > I think remove will have more functions since I am getting rid of
> > devm_add_action_or_reset()
> 
> See above.
> 
> J
> 
> >
> > >
> > > > +
> > > > +	return 0;
> > > > +}
> > > > +
> > >
> > > ...

Thanks,
Anand