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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Thu, 17 Oct 2019 15:47:47 +0200
Message-ID: <CAK8P3a3+UrqS0nQxcG7UuMt4s5FDnowFq-C5-K5XU-CKpciM8g@mail.gmail.com>
Subject: Re: [PATCH 3/3] crypto: inside-secure - Remove #ifdef checks
To:     Pascal Van Leeuwen <pvanleeuwen@verimatrix.com>
Cc:     Antoine Tenart <antoine.tenart@bootlin.com>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        "David S. Miller" <davem@davemloft.net>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Pascal van Leeuwen <pascalvanl@gmail.com>,
        Kelsey Skunberg <skunberg.kelsey@gmail.com>,
        "linux-crypto@vger.kernel.org" <linux-crypto@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>
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Sender: linux-kernel-owner@vger.kernel.org
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On Thu, Oct 17, 2019 at 3:26 PM Pascal Van Leeuwen
<pvanleeuwen@verimatrix.com> wrote:

> >       /* Register PCI driver */
> > -     pcireg_rc = pci_register_driver(&safexcel_pci_driver);
> > -#endif
> > +     ret = pci_register_driver(&safexcel_pci_driver);
> >
> > -#if IS_ENABLED(CONFIG_OF)
> >       /* Register platform driver */
> > -     ofreg_rc = platform_driver_register(&crypto_safexcel);
> > - #if IS_ENABLED(CONFIG_PCI)
> > -     /* Return success if either PCI or OF registered OK */
> > -     return pcireg_rc ? ofreg_rc : 0;
> > - #else
> > -     return ofreg_rc;
> > - #endif
> > -#else
> > - #if IS_ENABLED(CONFIG_PCI)
> > -     return pcireg_rc;
> > - #else
> > -     return -EINVAL;
> > - #endif
> > -#endif
> > +     if (IS_ENABLED(CONFIG_OF) && !ret) {
> >
> Hmm ... this would make it skip the OF registration if the PCIE
> registration failed. Note that the typical embedded  system will
> have a PCIE subsystem (e.g. Marvell A7K/A8K does) but will have
> the EIP embedded on the SoC as an OF device.
>
> So the question is: is it possible somehow that PCIE registration
> fails while OF registration does pass? Because in that case, this
> code would be wrong ...

I don't see how it would fail. When CONFIG_PCI is disabled,
pci_register_driver() does nothing, and the pci_driver as well
as everything referenced from it will be silently dropped from
the object file.
If CONFIG_PCI is enabled, then the driver will be registered
to the PCI subsystem, waiting for a device to show up, but
the driver registration does not care about whether there is
such a device.

> Other than that, I don't care much how this code is implemented
> as long as it works for both my use cases, being an OF embedded
> device (on a SoC _with_ or _without_ PCIE support) and a device
> on a PCIE board in a PCI (which has both PCIE and OF support).

Yes, that should be fine. There are a lot of drivers that support
multiple bus interfaces, and this is the normal way to handle them.

    Arnd