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

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Date:	Mon, 15 Sep 2014 23:55:28 +0200
From:	Frans Klaver <fransklaver@...il.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Darren Hart <dvhart@...radead.org>,
	Corentin Chary <corentin.chary@...il.com>,
	Rafael Wysocki <rafael.j.wysocki@...el.com>,
	acpi4asus-user@...ts.sourceforge.net,
	platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org, "H. Peter Anvin" <hpa@...ux.intel.com>
Subject: Re: [PATCH 10/13] eeepc-laptop: compare proper return values in
 get_cpufv

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:
> > On Sat, Sep 13, 2014 at 01:06:49AM +0200, Frans Klaver wrote:
> > > In get_cpufv the return value of get_acpi is stored in the cpufv struct.
> > > Right before this value is checked for errors, it is and'ed with 0xff.
> > > This means c->cur can never be less than zero. Besides that, the actual
> > > error value is ignored.
> > > 
> > > c->num is also and'ed with 0xff, which means we can ignore values below
> > > zero.
> > > 
> > > Check the result of get_acpi() right away. While at it, propagate the
> > > error if we got one.
> > > 
> > > Signed-off-by: Frans Klaver <fransklaver@...il.com>
> > > ---
> > >  drivers/platform/x86/eeepc-laptop.c | 5 ++++-
> > >  1 file changed, 4 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/platform/x86/eeepc-laptop.c b/drivers/platform/x86/eeepc-laptop.c
> > > index 47488d3..828db56 100644
> > > --- a/drivers/platform/x86/eeepc-laptop.c
> > > +++ b/drivers/platform/x86/eeepc-laptop.c
> > > @@ -332,9 +332,12 @@ struct eeepc_cpufv {
> > >  static int get_cpufv(struct eeepc_laptop *eeepc, struct eeepc_cpufv *c)
> > >  {
> > >  	c->cur = get_acpi(eeepc, CM_ASL_CPUFV);
> > > +	if (c->cur < 0)
> > > +		return c->cur;
> > > +
> > >  	c->num = (c->cur >> 8) & 0xff;
> > >  	c->cur &= 0xff;
> > > -	if (c->cur < 0 || c->num <= 0 || c->num > 12)
> > > +	if (c->num == 0 || c->num > 12)
> > >  		return -ENODEV;
> > >  	return 0;
> > 
> > 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.

Thanks,
Frans
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