linux-kernel - Re: [PATCH 1/2] i2c: piix4: Use request_muxed

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Date:   Wed, 14 Feb 2018 15:23:05 +0100
From:   Jean Delvare <jdelvare@...e.de>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Wolfram Sang <wsa@...-dreams.de>,
        Zoltán Böszörményi 
        <zboszor@...hu>, linux-i2c@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] i2c: piix4: Use request_muxed_region

On Mon, 12 Feb 2018 10:51:52 -0800, Guenter Roeck wrote:
> On Mon, Feb 12, 2018 at 11:10:41AM +0100, Jean Delvare wrote:
> > On Sat, 30 Dec 2017 08:50:57 -0800, Guenter Roeck wrote:  
> > > @@ -298,12 +295,15 @@ static int piix4_setup_sb800(struct pci_dev *PIIX4_dev,
> > >  	else
> > >  		smb_en = (aux) ? 0x28 : 0x2c;
> > >  
> > > -	mutex_lock(&piix4_mutex_sb800);
> > > +	if (!request_muxed_region(SB800_PIIX4_SMB_IDX, 2, "sb800_piix4_smb"))
> > > +		return -EBUSY;  
> > 
> > This would happen if and only if another driver has requested the
> > region already but without IORESOURCE_MUXED, right? Don't you want to  
> 
> Or if its call to alloc_resource() fails.

OK, two things which are not supposed to happen, so failing is the
right thing to do.

> > write an error message then? I don't think request_muxed_region() will
> > do, and probe failing with -EBUSY but no error message logged would be
> > hard to diagnose.
>
> NP, though the analysis is quite simple - /proc/iomem will show the culprit.

I'm confused. How would the user know what to look for in /proc/iomem
(or, I believe, /proc/ioports actually) if the driver does not print
which resource allocation failed?

If the information is already printed somewhere, then I agree there's no
point adding a message. But from the code I could not find it.

-- 
Jean Delvare
SUSE L3 Support