Re: [PATCH 10/13] eeepc-laptop: compare proper return values in get_cpufv

From: Darren Hart <dvhart@infradead.org>
To: Frans Klaver <fransklaver@gmail.com>, Paul Bolle <pebolle@tiscali.nl>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Corentin Chary <corentin.chary@gmail.com>,
	Rafael Wysocki <rafael.j.wysocki@intel.com>,
	acpi4asus-user <acpi4asus-user@lists.sourceforge.net>,
	platform-driver-x86 <platform-driver-x86@vger.kernel.org>,
	linux-kernel@vger.kernel.org,
	linux-acpi <linux-acpi@vger.kernel.org>,
	"H. Peter Anvin" <hpa@linux.intel.com>
Subject: Re: [PATCH 10/13] eeepc-laptop: compare proper return values in get_cpufv
Date: Tue, 16 Sep 2014 16:39:46 -0700	[thread overview]
Message-ID: <20140916233946.GB18698@vmdeb7> (raw)
In-Reply-To: <20140916211001.GA23674@gmail.com>

On Tue, Sep 16, 2014 at 11:10:01PM +0200, Frans Klaver wrote:
> On Tue, Sep 16, 2014 at 01:52:47PM -0700, Darren Hart wrote:
> > On Tue, Sep 16, 2014 at 01:54:25PM +0200, Frans Klaver wrote:
> > > On Mon, Sep 15, 2014 at 11:55 PM, Frans Klaver <fransklaver@gmail.com> wrote:
> > > > On Mon, Sep 15, 2014 at 02:51:25PM -0700, Greg Kroah-Hartman wrote:
> > > >> On Mon, Sep 15, 2014 at 02:49:02PM -0700, Darren Hart wrote:
> > > >> >
> > > >> > This patch is fine as is. However, Greg has supported propogating the error code
> > > >> > through to the sysfs interface (if I understand him correctly on an earlier post
> > > >> > to this list). This would require an addition change to this patch would
> > > >> > propogated the get_cpufv error code in show_available_cpuv(), show_cpuv(), and
> > > >> > store_cpuv(). As it is, we return -ENODEV on any failure, where an ACPI call
> > > >> > error should probably return -ENXIO as I understand it.
> > > >>
> > > >> I really have no idea at this point in time what to recommend.  How
> > > >> about just stick with what is happening today so that:
> > > >>
> > > >> > However, there was a rather famous change in error code handling in which pulse
> > > >> > audio broke and Linus was very upset with one of his maintainers.
> > > >>
> > > >> That doesn't happen :)
> > > >
> > > > So if I interpret that correctly, we're dropping the last patch
> > > > (ENODEV -> ENXIO) from the series? That's fine by me. As mentioned
> > > > earlier, I already saw something else break because I returned ENXIO
> > > > instead of ENODEV.
> > > >
> > > > Maybe it's a good idea to try and document the expected behavior
> > > > somewhere, if even Greg isn't sure what to do.
> > > 
> > > For good measure:
> > > 
> > > v2 will not change the return values at the sysfs interface, meaning
> > > we will always return -ENODEV on error. I am going to try to keep as
> > > much internal functions propagating errors as possible though, unless
> > > someone strongly disagrees.
> > > 
> > > Thanks,
> > > Frans
> > 
> > I cornered Linus today and asked about this specifically. The policy is this:
> > 
> > Don't change the sysfs return codes without good reason. A good reason could be
> > a real bug or problem with the return codes. It could also be to consolidate
> > error handling which makes things more uniform, etc.
> > 
> > If this results in broken userspace, the maintainer will revert the change.
> 
> Alright, that is basically what I was expecting it to be. As it happens,
> this also means that we'll have to decide what to do about returning
> -EIO/-ENODEV/rv in show_sys_acpi and store_sys_acpi. The latter was
> changed by Paul Bolle's "eeepc-laptop: simplify parse_arg()". The return
> value of these functions is propagated to the sysfs interface.

Yes, that change to store_sys_acpi needs to be reverted. I don't think
show_sys_acpi is actually changed in that patch.

Paul, can you resend that patch with the store_sys_acpi() -EIO return restored?

-- 
Darren Hart
Intel Open Source Technology Center