linux-kernel - Re: [PATCH 2/4] powerpc/vas: Fix cleanup when VAS is not configured

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Message-Id: <20180212202510.GB28183@us.ibm.com>
Date:   Mon, 12 Feb 2018 12:25:10 -0800
From:   Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        mikey@...ling.org, hbabu@...ibm.com, linuxppc-dev@...abs.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] powerpc/vas: Fix cleanup when VAS is not configured

Michael Ellerman [mpe@...erman.id.au] wrote:
> Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com> writes:
> 
> > When VAS is not configured in the system, make sure to remove
> > the VAS debugfs directory and unregister the platform driver.
> >
> > Signed-off-by: Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
> ...
> > diff --git a/arch/powerpc/platforms/powernv/vas.c b/arch/powerpc/platforms/powernv/vas.c
> > index aebbe95..f83e27d8 100644
> > --- a/arch/powerpc/platforms/powernv/vas.c
> > +++ b/arch/powerpc/platforms/powernv/vas.c
> > @@ -169,8 +169,11 @@ static int __init vas_init(void)
> >  		found++;
> >  	}
> >  
> > -	if (!found)
> > +	if (!found) {
> > +		platform_driver_unregister(&vas_driver);
> > +		vas_cleanup_dbgdir();
> >  		return -ENODEV;
> > +	}
> 
> The better patch would be to move the call to vas_init_dbgdir() down
> here, where we know we have successfully registered the driver.

Well, when VAS is configured, init_vas_instance() expects the top level
"vas" debugfs dir to already be setup.

We could have each init_vas_instance() assume it is the first and
unconditionally call vas_init_dbgdir(). vas_init_dbgdir() could make
sure to initialize only once.

Or, we could make a separate pass countng "ibm,vas" nodes. If there are
none, skip both steps (dbgdir and registering platform driver).

Sukadev