linux-kernel - Re: [alsa-devel] regression v4.16 on Nokia N900: sound does not work

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Date:   Fri, 2 Mar 2018 17:53:21 +0100
From:   Pavel Machek <pavel@....cz>
To:     "Andrew F. Davis" <afd@...com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Daniel Baluta <daniel.baluta@...il.com>,
        Thorsten Leemhuis <regressions@...mhuis.info>,
        Peter Ujfalusi <peter.ujfalusi@...com>,
        Linux-ALSA <alsa-devel@...a-project.org>,
        Ivajlo Dimitrov <ivo.g.dimitrov.75@...il.com>,
        Kevin Hilman <khilman@...nel.org>,
        ext Tony Lindgren <tony@...mide.com>,
        Aaro Koskinen <aaro.koskinen@....fi>,
        kernel list <linux-kernel@...r.kernel.org>,
        Sebastian Reichel <sre@...nel.org>,
        Martijn Braam <martijn@...xit.nl>,
        Filip Matijević <filip.matijevic.pz@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Mickuláš Qwertz <abcloriens@...il.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Pali Rohár <pali.rohar@...il.com>,
        clayton@...ftyguy.net, Linux-OMAP <linux-omap@...r.kernel.org>,
        Patrik Bachan <patrikbachan@...il.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        serge@...lyn.com
Subject: Re: [alsa-devel] regression v4.16 on Nokia N900: sound does not work

On Fri 2018-03-02 08:22:52, Andrew F. Davis wrote:
> On 03/02/2018 05:10 AM, Pavel Machek wrote:
> > Hi!
> > 
> >>> If this is taking longer to fix, should c85823390215 be reverted in
> >>> the meantime? It does not seem particulary important/urgent...
> >>
> >> No patience between the v4.16 release candidates eh ;)
> >>
> >> commit 6662ae6af82df10259a70c7569b4c12ea7f3ba93
> >> ("gpiolib: Keep returning EPROBE_DEFER when we should")
> >>
> >> and
> >>
> >> commit ce27fb2c56db6ccfe8099343bb4afdab15e77e7b
> >> ("gpio: Handle deferred probing in of_find_gpio() properly")
> >>
> >> that are both in Torvalds' tree since yesterday should be fixing
> >> this, I think? Did you try just using the upstream HEAD?
> > 
> > Ok, so this code looks pretty crazy to me: I tried removing the
> > "of_find_spi_gpio" part, and audio started working.
> > 
> > What is going on with the ()s around == s? You made me look up C
> > operator precedence.
> > 
> > Hmm, and it is also wrong, right? It turns any error code into ENOENT,
> > as it tries to do the "special handling".
> > 
> >                  *                                                                      
> >                  * This means we don't need to look any further for                     
> >                  * alternate name conventions, and we should really                     
> >                  * preserve the return code for our user to be able to                  
> >                  * retry probing later.                                                 
> >                  */
> >                 if (IS_ERR(desc) && PTR_ERR(desc) == -EPROBE_DEFER)
> >                         return desc;
> > 
> >                 if (!IS_ERR(desc) || (PTR_ERR(desc) != -ENOENT))
> >                         break;
> >         }
> > 
> >         /* Special handling for SPI GPIOs if used */
> >         if (IS_ERR(desc))
> >                 desc = of_find_spi_gpio(dev, con_id, &of_flags);
> > 
> >         /* Special handling for regulator GPIOs if used */
> >         if (IS_ERR(desc) && PTR_ERR(desc) != -EPROBE_DEFER)
> >                 desc = of_find_regulator_gpio(dev, con_id, &of_flags);
> > 
> > Something like this?
> > 
> > diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c
> > index 84e5a9d..f0fab26 100644
> > --- a/drivers/gpio/gpiolib-of.c
> > +++ b/drivers/gpio/gpiolib-of.c
> > @@ -241,29 +241,17 @@ struct gpio_desc *of_find_gpio(struct device *dev, const char *con_id,
> >  
> >  		desc = of_get_named_gpiod_flags(dev->of_node, prop_name, idx,
> >  						&of_flags);
> > -		/*
> > -		 * -EPROBE_DEFER in our case means that we found a
> > -		 * valid GPIO property, but no controller has been
> > -		 * registered so far.
> > -		 *
> > -		 * This means we don't need to look any further for
> > -		 * alternate name conventions, and we should really
> > -		 * preserve the return code for our user to be able to
> > -		 * retry probing later.
> > -		 */
> > -		if (IS_ERR(desc) && PTR_ERR(desc) == -EPROBE_DEFER)
> > -			return desc;
> >  
> > -		if (!IS_ERR(desc) || (PTR_ERR(desc) != -ENOENT))
> > +		if (!IS_ERR(desc) || PTR_ERR(desc) != -ENOENT)
> 
> 
> I rather like the () so one doesn't always have to look up C operator
> precedence to verify..

Well, Ok, but then the ()s should be at the other ifs nearby, too. See?

> 
> >  			break;
> >  	}
> >  
> >  	/* Special handling for SPI GPIOs if used */
> > -	if (IS_ERR(desc))
> > +	if (IS_ERR(desc) && PTR_ERR(desc) == -ENOENT)
> >  		desc = of_find_spi_gpio(dev, con_id, &of_flags);
> >  
> >  	/* Special handling for regulator GPIOs if used */
> > -	if (IS_ERR(desc) && PTR_ERR(desc) != -EPROBE_DEFER)
> > +	if (IS_ERR(desc) && PTR_ERR(desc) == -ENOENT)
> >  		desc = of_find_regulator_gpio(dev, con_id, &of_flags);
> >  
> >  	if (IS_ERR(desc))
> >
									Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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