linux-kernel - Re: [PATCH] tpm: remove chip_num parameter from in-kernel API

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Message-ID: <20171024222741.lqvgpdaosjazpvfd@linux.intel.com>
Date:   Wed, 25 Oct 2017 00:27:41 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Jason Gunthorpe <jgunthorpe@...idianresearch.com>
Cc:     linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        Matt Mackall <mpm@...enic.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Peter Huewe <peterhuewe@....de>,
        Marcel Selhorst <tpmdd@...horst.net>,
        Mimi Zohar <zohar@...ux.vnet.ibm.com>,
        Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
        James Morris <james.l.morris@...cle.com>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        David Howells <dhowells@...hat.com>,
        Jerry Snitselaar <jsnitsel@...hat.com>,
        "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" 
        <linux-crypto@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:KEYS-TRUSTED" <keyrings@...r.kernel.org>
Subject: Re: [PATCH] tpm: remove chip_num parameter from in-kernel API

On Tue, Oct 24, 2017 at 12:52:08PM -0600, Jason Gunthorpe wrote:
> On Mon, Oct 23, 2017 at 02:38:14PM +0200, Jarkko Sakkinen wrote:
> > The reasoning is simple and obvious. Since every call site passes the
> > value TPM_ANY_NUM (0xFFFF) the parameter does not have right to exist.
> > Refined the documentation of the corresponding functions.
> 
> I like this patch, but how about a slightly different take, make this
> change instead:
> 
> -struct tpm_chip *tpm_chip_find_get(int chip_num)
> +struct tpm_chip *tpm_chip_find_get(struct tpm_chip *chip);
> 
> Where chip == NULL means the default TPM.
> 
> And then at all call sites swap TPM_ANY_NUM to NULL and instead of
> flowing an 'int chip_num' to tpm_chip_find_get, flow the 'struct
> tpm_chip *' directly.
> 
> This gets us much closer to the desired API with about the same amount
> of churn as this patch has.
> 
> Jason

I can do that. I will rework this as a patch set that includes this
proposal. Gives us more clean position to continue. Thank you.

/Jarkko