linux-kernel - Re: [PATCH 2/5] i2c-mux-gpio: Return an error if no config data found

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Message-ID: <20190425154736.emjumxqimzgvzrla@mobilestation>
Date:   Thu, 25 Apr 2019 18:47:48 +0300
From:   Serge Semin <fancer.lancer@...il.com>
To:     Peter Rosin <peda@...ntia.se>
Cc:     Peter Korsgaard <peter.korsgaard@...co.com>,
        Serge Semin <Sergey.Semin@...latforms.ru>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/5] i2c-mux-gpio: Return an error if no config data found

On Wed, Apr 24, 2019 at 09:25:50PM +0000, Peter Rosin wrote:
> On 2019-04-24 14:34, Serge Semin wrote:
> > It's pointless and might be even errors prone to proceed with further
> > initialization if neither of- no platform-based settings were discovered.
> > Just return an error in this case.
> > 
> > Signed-off-by: Serge Semin <fancer.lancer@...il.com>
> > ---
> >  drivers/i2c/muxes/i2c-mux-gpio.c | 12 +++++++-----
> >  1 file changed, 7 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/i2c/muxes/i2c-mux-gpio.c b/drivers/i2c/muxes/i2c-mux-gpio.c
> > index 24cf6ec02e75..a14fe132b0c3 100644
> > --- a/drivers/i2c/muxes/i2c-mux-gpio.c
> > +++ b/drivers/i2c/muxes/i2c-mux-gpio.c
> > @@ -132,7 +132,7 @@ static int i2c_mux_gpio_probe_dt(struct gpiomux *mux,
> >  static int i2c_mux_gpio_probe_dt(struct gpiomux *mux,
> >  					struct platform_device *pdev)
> >  {
> > -	return 0;
> > +	return -EINVAL;
> >  }
> >  #endif
> >  
> > @@ -142,6 +142,9 @@ static int i2c_mux_gpio_probe_plat(struct gpiomux *mux,
> >  	struct i2c_mux_gpio_platform_data *data = dev_get_platdata(&pdev->dev);
> >  	struct gpio_chip *gpio;
> >  
> > +	if (!data)
> > +		return -EINVAL;
> > +
> >  	/*
> >  	 * If a GPIO chip name is provided, the GPIO pin numbers provided are
> >  	 * relative to its base GPIO number. Otherwise they are absolute.
> > @@ -175,11 +178,10 @@ static int i2c_mux_gpio_probe(struct platform_device *pdev)
> >  	if (!mux)
> >  		return -ENOMEM;
> >  
> > -	if (!dev_get_platdata(&pdev->dev))
> > +	ret = i2c_mux_gpio_probe_plat(mux, pdev);
> > +	if (ret)
> >  		ret = i2c_mux_gpio_probe_dt(mux, pdev);
> > -	else
> > -		ret = i2c_mux_gpio_probe_plat(mux, pdev);
> > -	if (ret < 0)
> > +	if (ret)
> >  		return ret;
> 
> I notice that after this patch, all probe failures from non-dt configs
> will return -EINVAL from the dummy i2c_mux_gpio_probe_dt that gets
> called on i2c_mux_gpio_probe_plat failure.
> 
> So, any -EPROBE_DEFER is now lost. That probably doesn't fly.
> 

So what do you suggest then? We can return to something like:
if (dev_get_platdata(&pdev->dev))
    ret = i2c_mux_gpio_probe_plat(mux, pdev);
else
    ret = i2c_mux_gpio_probe_dt(mux, pdev);

In this case there is no falling back to dt. Just either plat- or of-based
initialization. The same can be done for i2c_mux_gpio_request_*() methods.

-Sergey

> Cheers,
> Peter
> 
> >  
> >  	parent = i2c_get_adapter(mux->data.parent);
> > 
>