Re: [PATCH 4.19 309/639] hwmon: (w83627hf) Use request_muxed_region for Super-IO accesses

[Guenter Roeck <linux@xxxxxxxxxxxx>]

On 1/25/20 10:59 AM, Pavel Machek wrote:
> Hi!
> > [ Upstream commit e95fd518d05bfc087da6fcdea4900a57cfb083bd ]
> >
> > Super-IO accesses may fail on a system with no or unmapped LPC bus.
> >
> > Also, other drivers may attempt to access the LPC bus at the same time,
> > resulting in undefined behavior.
> >
> > Use request_muxed_region() to ensure that IO access on the requested
> > address space is supported, and to ensure that access by multiple drivers
> > is synchronized.
>
> > @@ -1644,9 +1654,21 @@ static int w83627thf_read_gpio5(struct platform_device *pdev)
> >   	struct w83627hf_sio_data *sio_data = dev_get_platdata(&pdev->dev);
> >   	int res = 0xff, sel;
> >   
> > -	superio_enter(sio_data);
> > +	if (superio_enter(sio_data)) {
> > +		/*
> > +		 * Some other driver reserved the address space for itself.
> > +		 * We don't want to fail driver instantiation because of that,
> > +		 * so display a warning and keep going.
> > +		 */
> > +		dev_warn(&pdev->dev,
> > +			 "Can not read VID data: Failed to enable SuperIO access\n");
> > +		return res;
> > +	}
> > +
> >   	superio_select(sio_data, W83627HF_LD_GPIO5);
> >   
> > +	res = 0xff;
> > +
>
> This is strange. res is not actually assigned in the code above, so we
> have res = 0xff twice. Can we remove one of the initializations and do
> 'return 0xff' directly to make code more clear?
>
>
> > @@ -1677,7 +1699,17 @@ static int w83687thf_read_vid(struct platform_device *pdev)
> >   	struct w83627hf_sio_data *sio_data = dev_get_platdata(&pdev->dev);
> >   	int res = 0xff;
> >   
> > -	superio_enter(sio_data);
> > +	if (superio_enter(sio_data)) {
> > +		/*
> > +		 * Some other driver reserved the address space for itself.
> > +		 * We don't want to fail driver instantiation because of that,
> > +		 * so display a warning and keep going.
> > +		 */
> > +		dev_warn(&pdev->dev,
> > +			 "Can not read VID data: Failed to enable SuperIO access\n");
> > +		return res;
> > +	}
>
> Direct "return 0xff" would make more sense here, too.

Please feel free to submit a patch to improve the upstream code.

Thanks,
Guenter