linux-kernel - Re: [PATCH] Silence 'ignoring return value' warnings in drivers/video/aty/radeon

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Date:	Tue, 6 May 2008 21:00:55 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	David Miller <davem@...emloft.net>, tony@...eyournoodle.com,
	linux-kernel@...r.kernel.org, benh@...nel.crashing.org
Subject: Re: [PATCH] Silence 'ignoring return value' warnings in
 drivers/video/aty/radeon_base.c

On Tue, 6 May 2008 14:56:08 -0700
Andrew Morton <akpm@...ux-foundation.org> wrote:

> On Tue, 06 May 2008 14:43:01 -0700 (PDT)
> David Miller <davem@...emloft.net> wrote:
> 
> > From: Andrew Morton <akpm@...ux-foundation.org>
> > Date: Tue, 6 May 2008 14:39:36 -0700
> > 
> > > On Thu, 24 Apr 2008 14:34:01 +1000
> > > tony@...eyournoodle.com (Tony Breeds) wrote:
> > > 
> > > > Current kernel builds warn about:
> > > > drivers/video/aty/radeon_base.c: In function
> > > > 'radeonfb_pci_register': drivers/video/aty/radeon_base.c:2334:
> > > > warning: ignoring return value of 'sysfs_create_bin_file',
> > > > declared with attribute warn_unused_result
> > > > drivers/video/aty/radeon_base.c:2336: warning: ignoring return
> > > > value of 'sysfs_create_bin_file', declared with attribute
> > > > warn_unused_result
> > > > 
> > > > Do minimal checking of these functions and issue a warning if
> > > > either fails.  They don't seem to be critical..
> > > 
> > > well OK, but I object to the patch title!
> > > 
> > > The point isn't to silence warnings.  It is to fix the problem
> > > which that warning is drawing our attention to.
> > > 
> > > So I rewrote the title to "drivers/video/aty/radeon_base.c:
> > > notify user if sysfs_create_bin_file() failed".
> > > 
> > > And your fix looks appropriate - if sysfs_create_bin_file() fails
> > > we will now get reports of this and we can find out what kernel
> > > bug caused this to happen.
> > 
> > The last time someone "fixed" this warning in the radeon driver,
> > people lost their consoles.
> > 
> > Just giving a heads up...
> 
> heh, thanks.
> 
> This one just emits a warning:
> 
> @@ -2340,9 +2341,12 @@ static int __devinit radeonfb_pci_regist
>  
>  	/* Register some sysfs stuff (should be done better) */
>  	if (rinfo->mon1_EDID)
> -		sysfs_create_bin_file(&rinfo->pdev->dev.kobj,
> &edid1_attr);
> +		err |= sysfs_create_bin_file(&rinfo->pdev->dev.kobj,
> &edid1_attr); if (rinfo->mon2_EDID)
> -		sysfs_create_bin_file(&rinfo->pdev->dev.kobj,
> &edid2_attr);
> +		err |= sysfs_create_bin_file(&rinfo->pdev->dev.kobj,
> &edid2_attr);
> +	if (err)
> +		pr_warning("%s() Creating sysfs files failed,
> continuing\n",
> +		           __func__);
>  
>  	/* save current mode regs before we switch into the new one
>  	 * so we can restore this upon __exit
> _
> 
> 
> So from what you say, it sounds like we will be seeing that warning.
> I wonder why.

can we make it a WARN_ON() as well? that way we'll see it in various
kerneloops.org stats etc etc.. and we also get a nice backtrace for
free to go with it....

(rationale: users tend to not read their dmesg much, but WARN_ON()'s do
get noticed)
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