linux-kernel - Re: [PATCH v3 1/2] mfd: arizona: Update reset pin to use GPIOD

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Message-ID: <20180307162537.pryp3qz3lgm7a4zs@dell>
Date:   Wed, 7 Mar 2018 16:25:37 +0000
From:   Lee Jones <lee.jones@...aro.org>
To:     Charles Keepax <ckeepax@...nsource.cirrus.com>
Cc:     robh+dt@...nel.org, mark.rutland@....com, linus.walleij@...aro.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        patches@...nsource.cirrus.com
Subject: Re: [PATCH v3 1/2] mfd: arizona: Update reset pin to use GPIOD

On Wed, 07 Mar 2018, Charles Keepax wrote:

> On Wed, Mar 07, 2018 at 01:28:12PM +0000, Lee Jones wrote:
> > On Tue, 20 Feb 2018, Charles Keepax wrote:
> > > +	if (IS_ERR(pdata->reset)) {
> > > +		ret = PTR_ERR(pdata->reset);
> > > +		switch (ret) {
> > > +		case -ENOENT:
> > > +		case -ENOSYS:
> > > +			break;
> > > +		case -EPROBE_DEFER:
> > > +			return ret;
> > > +		default:
> > > +			dev_err(arizona->dev, "Reset GPIO malformed: %d\n",
> > > +				ret);
> > > +			break;
> > > +		}
> > 
> > I haven't seen a switch statement used in the error handling path
> > before.  There is probably good reason for that.
> > 
> 
> There are a fair few of them "grep -rI "switch (ret)" | wc -l" ==
> 205. Although to be fair that has rarely been an argument in
> somethings favour.

I didn't say "it has never been done", just that I hadn't seen it.

Besides, 205 uses is a very small amount in kernel code:

`git grep "if (ret" | wc -l` == 74710

> > What is the 'default' case?  -EINVAL?
> > 
> 
> I would guess most of the time yes, but I would rather not assume
> that. I can redo this as if's if you prefer it that way? The if is
> slightly less lines although I do think the switch is much
> clearer as to intent.
> 
> if (ret == -EPROBE_DEFER) {
> 	return ret;
> } else if (ret != -ENOENT && ret != -ENOSYS {
> 	dev_err(arizona->dev, ....);
> }

I don't know enough about the API to see why -ENOENT and -ENOSYS do
not deserve error messages.

What do the other users of the API do?

-- 
Lee Jones
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
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