[alsa-devel] [PATCH 1/2] ASoC: nuc900: Fix platform_get_irq() error checking some more

[Dan Carpenter]

On Mon, Dec 11, 2017 at 02:37:22PM +0530, Arvind Yadav wrote:
> Hi Dan,
> 
> 
> On Monday 11 December 2017 02:10 PM, Dan Carpenter wrote:
> > On Sun, Dec 10, 2017 at 08:10:26AM +0530, arvindY wrote:
> > > 
> > > On Sunday 10 December 2017 07:22 AM, Dan Carpenter wrote:
> > > > On Sat, Dec 09, 2017 at 06:27:32PM +0100, Alexandre Belloni wrote:
> > > > > > > diff --git a/sound/soc/nuc900/nuc900-ac97.c b/sound/soc/nuc900/nuc900-ac97.c
> > > > > > > index 5e4fbd2d3479..71fce7c85c93 100644
> > > > > > > --- a/sound/soc/nuc900/nuc900-ac97.c
> > > > > > > +++ b/sound/soc/nuc900/nuc900-ac97.c
> > > > > > > @@ -345,11 +345,10 @@ static int nuc900_ac97_drvprobe(struct platform_device *pdev)
> > > > > > >     		goto out;
> > > > > > >     	}
> > > > > > > -	nuc900_audio->irq_num = platform_get_irq(pdev, 0);
> > > > > > > -	if (nuc900_audio->irq_num <= 0) {
> > > > > > > -		ret = nuc900_audio->irq_num < 0 ? nuc900_audio->irq_num : -EBUSY;
> > > > > > > +	ret = platform_get_irq(pdev, 0);
> > > > > > > +	if (ret < 0)
> > > > > The <= 0 was ok, see:
> > > > > https://lkml.org/lkml/2017/11/18/41
> > > > > 
> > > > Yeah, but is it ever going to return 0?  That seems like a design error
> > > > and also really crap commenting if so
> > > yes, It can return 0 on sprac platform and If you see the return of
> > > platform_get_irq() 'return r ? r->start : -ENXIO;'. It should be
> > > 'return r && r->start? r->start : -ENXIO;'. We can not add checks here,
> > > Because There's a bunch of platforms in the kernel they still use IRQ0 as
> > > valid.
> > > I have separate mails where few maintainer ask me to add check for 0 and few
> > > not.
> > > Adding check for 0 will never harm.
> > What you're saying doesn't make sense.
> I am following a below link. Where they have point out irq 0 is not valid.
> https://lwn.net/Articles/470820/

That article is interesting and explains why this stuff is so messed up,
but I think my email is correct.  No one is going to tell the kernel,
"There is an IRQ resource at 0, please store it in r->start.  We can't
use that IRQ, it's only there to make the kernel crash when people call
platform_get_irq()!  #geniusidea."

There are other IRQ functions like irq_of_parse_and_map() which do
return zero on error but platform_get_irq() pretty clearly returns
negative error codes.

regards,
dan carpenter