linux-kernel - Re: [PATCH v3] eeepc-laptop: simplify parse

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Date:	Wed, 17 Sep 2014 13:14:36 -0700
From:	Darren Hart <dvhart@...radead.org>
To:	Paul Bolle <pebolle@...cali.nl>
Cc:	Corentin Chary <corentin.chary@...il.com>,
	Frans Klaver <fransklaver@...il.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Matthew Garrett <matthew.garrett@...ula.com>,
	Rafael Wysocki <rafael.j.wysocki@...el.com>,
	acpi4asus-user@...ts.sourceforge.net,
	platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] eeepc-laptop: simplify parse_arg()

On Wed, Sep 17, 2014 at 09:02:51PM +0200, Paul Bolle wrote:
> parse_arg() has three possible return values:
>     -EINVAL if sscanf(), in short, fails;
>     zero if "count" is zero; and
>     "count" in all other cases
> 
> But "count" will never be zero. See, parse_arg() is called by the
> various store functions. And the callchain of these functions starts
> with sysfs_kf_write(). And that function checks for a zero "count". So
> we can stop checking for a zero "count", drop the "count" argument
> entirely, and transform parse_arg() into a function that returns zero on
> success or a negative error. That, in turn, allows to make those store
> functions just return "count" on success. The net effect is that the
> code becomes a bit easier to understand.
> 
> A nice side effect is that this GCC warning is silenced too:
>     drivers/platform/x86/eeepc-laptop.c: In function ‘store_sys_acpi’:
>     drivers/platform/x86/eeepc-laptop.c:279:10: warning: ‘value’ may be used uninitialized in this function [-Wmaybe-uninitialized]
>       int rv, value;
> 
> Which is, of course, the reason to have a look at parse_arg().
> 
> Signed-off-by: Paul Bolle <pebolle@...cali.nl>
> ---
> Still build tested only, but now on top of v3.17-rc5. Has Frans tested
> writing zero length values to these sysfs files?
> 
> v3: store_sys_acpi() again returns -EIO if set_acpi() fails.
> 
> v2: let store_sys_acpi() return whatever error set_acpi() returns
> instead of remapping it to EIO. The new line about that in the commit
> explanation is silly, but I couldn't come up with a better explanation.

Queued, thanks.

-- 
Darren Hart
Intel Open Source Technology Center
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