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Date: Mon, 4 Mar 2024 07:57:03 +0100
From: Lukas Wunner <lukas@wunner.de>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Bjorn Helgaas <helgaas@kernel.org>, David Howells <dhowells@redhat.com>,
	David Woodhouse <dwmw2@infradead.org>,
	Herbert Xu <herbert@gondor.apana.org.au>,
	"David S. Miller" <davem@davemloft.net>,
	Alex Williamson <alex.williamson@redhat.com>,
	linux-pci@vger.kernel.org, linux-cxl@vger.kernel.org,
	linux-coco@lists.linux.dev, keyrings@vger.kernel.org,
	linux-crypto@vger.kernel.org, kvm@vger.kernel.org,
	Jonathan Cameron <Jonathan.Cameron@huawei.com>, linuxarm@huawei.com,
	David Box <david.e.box@intel.com>,
	Dave Jiang <dave.jiang@intel.com>, "Li, Ming" <ming4.li@intel.com>,
	Zhi Wang <zhi.a.wang@intel.com>,
	Alistair Francis <alistair.francis@wdc.com>,
	Wilfred Mallawa <wilfred.mallawa@wdc.com>,
	Alexey Kardashevskiy <aik@amd.com>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	Sean Christopherson <seanjc@google.com>,
	Alexander Graf <graf@amazon.com>
Subject: Re: [PATCH 03/12] X.509: Move certificate length retrieval into new
 helper
Message-ID: <20240304065703.GA24373@wunner.de>
References: <cover.1695921656.git.lukas@wunner.de>
 <16c06528d13b2c0081229a45cacd4b1b9cdff738.1695921657.git.lukas@wunner.de>
 <65205cc1c1f40_ae7e72949d@dwillia2-xfh.jf.intel.com.notmuch>
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On Fri, Oct 06, 2023 at 12:15:13PM -0700, Dan Williams wrote:
> Lukas Wunner wrote:
> > The upcoming in-kernel SPDM library (Security Protocol and Data Model,
> > https://www.dmtf.org/dsp/DSP0274) needs to retrieve the length from
> > ASN.1 DER-encoded X.509 certificates.
> > 
> > Such code already exists in x509_load_certificate_list(), so move it
> > into a new helper for reuse by SPDM.
[...]
> > +EXPORT_SYMBOL_GPL(x509_get_certificate_length);
> 
> Given CONFIG_PCI is a bool, is the export needed? Maybe save this export
> until the modular consumer arrives, or identify the modular consumer in the
> changelog?

The x509_get_certificate_length() helper introduced by this patch
isn't needed directly by the PCI core, but by the SPDM library.

The SPDM library is tristate and is selected by CONFIG_PCI_CMA,
which is indeed bool.

However SCSI and ATA (both tristate) have explicitly expressed an
interest to use the SPDM library.

If I drop the export, I'd have to declare the SPDM library bool.

I'm leaning towards keeping the SPDM library tristate (and keep the
export) to accommodate SCSI, ATA and possibly others.

Please let me know if you disagree.

Thanks,

Lukas