linux-kernel - Re: [PATCH] tpm: Move Linux RNG connection to hwrng

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Date:   Wed, 25 Oct 2017 09:18:59 -0600
From:   Jason Gunthorpe <jgunthorpe@...idianresearch.com>
To:     PrasannaKumar Muralidharan <prasannatsmkumar@...il.com>
Cc:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Stefan Berger <stefanb@...ux.vnet.ibm.com>,
        linux-integrity@...r.kernel.org,
        David Howells <dhowells@...hat.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
        open list <linux-kernel@...r.kernel.org>,
        linux-security-module@...r.kernel.org,
        "open list:KEYS-TRUSTED" <keyrings@...r.kernel.org>,
        "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" 
        <linux-crypto@...r.kernel.org>,
        James Morris <james.l.morris@...cle.com>,
        Matt Mackall <mpm@...enic.com>,
        David Safford <safford@...ibm.com>,
        Mimi Zohar <zohar@...ux.vnet.ibm.com>,
        "Serge E. Hallyn" <serge@...lyn.com>
Subject: Re: [PATCH] tpm: Move Linux RNG connection to hwrng

On Wed, Oct 25, 2017 at 08:15:09PM +0530, PrasannaKumar Muralidharan
wrote:

> > +static int tpm_add_hwrng(struct tpm_chip *chip)
> > +{
> > +       if (!IS_ENABLED(CONFIG_HW_RANDOM_TPM))
> > +               return 0;
> 
> Can #ifndef CONFIG_HW_RANDOM_TPM be used instead? That way an if
> condition can be avoided.

Generally speaking IS_ENABLED is prefered over #ifdef as it reduces the
set of compilation combinations.

Jason