linux-kernel - Re: mmotm 2011-03-02 - ACPI/sysfs WARNING with NVidia graphics card

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Date:	Thu, 03 Mar 2011 23:28:50 -0500
From:	Valdis.Kletnieks@...edu
To:	Greg KH <gregkh@...e.de>
Cc:	akpm@...ux-foundation.org, Len Brown <lenb@...nel.org>,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org
Subject: Re: mmotm 2011-03-02 - ACPI/sysfs WARNING with NVidia graphics card

On Thu, 03 Mar 2011 16:05:50 PST, Greg KH said:

> > [    0.818236] [Firmware Bug]: Duplicate ACPI video bus devices for the same VGA controller, please try module parameter "video.allow_duplicates=1"if the current driver doesn't work.
> 
> Have you tried this option?
> 
> There's nothing sysfs can do here, sorry, it really looks like you have
> a BIOS/firmware problem.

Well, (a) it's been saying "try it if the current driver doesn't work" - and
things have worked just fine all along (or more properly, if it's broken in
behavior, I haven't actually seen the effects...)

and (b) Something changed very recently to add the WARNING, which wasn't there
in rc5-next-2011022.

And (c) I doubt that's going to fix the WARNING, because looking at drivers/
acpi/video.c, the variable allow_duplicates is checked in exactly *ONE* place,
which is *after* the printk:

        if (status == AE_ALREADY_EXISTS) {
                printk(KERN_WARNING FW_BUG
                        "Duplicate ACPI video bus devices for the"
                        " same VGA controller, please try module "
                        "parameter \"video.allow_duplicates=1\""
                        "if the current driver doesn't work.\n");
                if (!allow_duplicates)
                        return -ENODEV;
        }

So since the warning triggers before we see the printk(), setting the variable
won't make a difference because we warn before we ever get into that if
statement.

Now, maybe we need to be checking allow_duplicates earlier and/or in other
places - but I'll let somebody who actually understands the code to decide taht. ;)

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