From: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Subject: Re: [PATCH] tpm: remove chip_num parameter from in-kernel API
Date: Tue, 24 Oct 2017 12:52:08 -0600
Message-ID: <20171024185208.GD1806@obsidianresearch.com>
References: <20171023123817.18559-1-jarkko.sakkinen@linux.intel.com>
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Cc: linux-integrity@vger.kernel.org,
        linux-security-module@vger.kernel.org,
        Matt Mackall <mpm@selenic.com>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Peter Huewe <peterhuewe@gmx.de>,
        Marcel Selhorst <tpmdd@selhorst.net>,
        Mimi Zohar <zohar@linux.vnet.ibm.com>,
        Dmitry Kasatkin <dmitry.kasatkin@gmail.com>,
        James Morris <james.l.morris@oracle.com>,
        "Serge E. Hallyn" <serge@hallyn.com>,
        David Howells <dhowells@redhat.com>,
        Jerry Snitselaar <jsnitsel@redhat.com>,
        "open list:HARDWARE RANDOM NUMBER GENERATOR CORE"
        <linux-crypto@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>,
        "open list:KEYS-TRUSTED" <keyrings@vger.kernel.org>
To: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
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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