linux-kernel - Re: checkpatch: false positives for else after return

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Message-ID: <1468855842.1900.14.camel@perches.com>
Date:	Mon, 18 Jul 2016 08:30:42 -0700
From:	Joe Perches <joe@...ches.com>
To:	Thierry Reding <thierry.reding@...il.com>,
	Andy Whitcroft <apw@...onical.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: checkpatch: false positives for else after return

On Mon, 2016-07-18 at 13:26 +0200, Thierry Reding wrote:
> Hi,
> 
> I've run across what I think is a false positive for checkpatch's
> UNNECESSARY_ELSE check. The code that triggers it is in the
> tegra_sor_probe() function in drivers/gpu/drm/tegra/sor.c. For
> reference, here's the code:
> 
> 	if (sor->soc->supports_hdmi) {
> 		sor->ops = &tegra_sor_hdmi_ops;
> 	} else if (sor->soc->supports_lvds) {
> 		dev_err(&pdev->dev, "LVDS not supported yet\n");
> 		return -ENODEV;
> 	} else {
> 		dev_err(&pdev->dev, "unknown (non-DP) support\n");
> 		return -ENODEV;
> 	}
> 
> For the first case (HDMI supported on SoC) the code should continue
> normally, but otherwise we need to error out because we don't support
> the configuration.
> 
> I can't come up with an alternative way of writing the above, and at the
> same time I can't see what's wrong with the above. It looks like a
> legitimate use of an else to me.
> 
> I made an attempt at fixing the check myself but failed miserably. Regex
> isn't among my strong skills =\
> 
> Any ideas on how to deal with this?

Hi Thierry.

Ignore checkpatch when it's wrong.

The message is:
"else is not generally useful after a break or return"
and that statement is true.

checkpatch is not, and will not become, a code flow
analysis tool.  It's a very brain-dead, stupid little
script that looks at very simple patch table rules.