RE: [PATCH 3/3] crypto: inside-secure - Remove #ifdef checks

[Pascal Van Leeuwen]

Hi Arnd,

Sorry for not responding earlier, but I've been very busy lately.
So I'm looking at this now for the first time.

> -----Original Message-----
> From: Arnd Bergmann <arnd@xxxxxxxx>
> Sent: Monday, September 30, 2019 2:15 PM
> To: Antoine Tenart <antoine.tenart@xxxxxxxxxxx>; Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>;
> David S. Miller <davem@xxxxxxxxxxxxx>; Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> Cc: Arnd Bergmann <arnd@xxxxxxxx>; Pascal Van Leeuwen <pvanleeuwen@xxxxxxxxxxxxxx>; Pascal van
> Leeuwen <pascalvanl@xxxxxxxxx>; Kelsey Skunberg <skunberg.kelsey@xxxxxxxxx>; linux-
> crypto@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux-pci@xxxxxxxxxxxxxxx
> Subject: [PATCH 3/3] crypto: inside-secure - Remove #ifdef checks
> 
> When both PCI and OF are disabled, no drivers are registered, and
> we get some unused-function warnings:
> 
> drivers/crypto/inside-secure/safexcel.c:1221:13: error: unused function
> 'safexcel_unregister_algorithms' [-Werror,-Wunused-function]
> static void safexcel_unregister_algorithms(struct safexcel_crypto_priv *priv)
> drivers/crypto/inside-secure/safexcel.c:1307:12: error: unused function
> 'safexcel_probe_generic' [-Werror,-Wunused-function]
> static int safexcel_probe_generic(void *pdev,
> drivers/crypto/inside-secure/safexcel.c:1531:13: error: unused function
> 'safexcel_hw_reset_rings' [-Werror,-Wunused-function]
> static void safexcel_hw_reset_rings(struct safexcel_crypto_priv *priv)
> 
> It's better to make the compiler see what is going on and remove
> such ifdef checks completely. In case of PCI, this is trivial since
> pci_register_driver() is defined to an empty function that makes the
> compiler subsequently drop all unused code silently.
> 
> The global pcireg_rc/ofreg_rc variables are not actually needed here
> since the driver registration does not fail in ways that would make
> it helpful.
> 
> For CONFIG_OF, an IS_ENABLED() check is still required, since platform
> drivers can exist both with and without it.
> 
> A little change to linux/pci.h is needed to ensure that
> pcim_enable_device() is visible to the driver. Moving the declaration
> outside of ifdef would be sufficient here, but for consistency with the
> rest of the file, adding an inline helper is probably best.
> 
> Fixes: 212ef6f29e5b ("crypto: inside-secure - Fix unused variable warning when CONFIG_PCI=n")
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> ---
>  drivers/crypto/inside-secure/safexcel.c | 49 ++++++-------------------
>  include/linux/pci.h                     |  1 +
>  2 files changed, 13 insertions(+), 37 deletions(-)
> 
> diff --git a/drivers/crypto/inside-secure/safexcel.c b/drivers/crypto/inside-secure/safexcel.c
> index 311bf60df39f..c4e8fd27314c 100644
> --- a/drivers/crypto/inside-secure/safexcel.c
> +++ b/drivers/crypto/inside-secure/safexcel.c
> @@ -1547,7 +1547,6 @@ static void safexcel_hw_reset_rings(struct safexcel_crypto_priv *priv)
>  	}
>  }
> 
> -#if IS_ENABLED(CONFIG_OF)
>  /* for Device Tree platform driver */
> 
>  static int safexcel_probe(struct platform_device *pdev)
> @@ -1666,9 +1665,7 @@ static struct platform_driver  crypto_safexcel = {
>  		.of_match_table = safexcel_of_match_table,
>  	},
>  };
> -#endif
> 
> -#if IS_ENABLED(CONFIG_PCI)
>  /* PCIE devices - i.e. Inside Secure development boards */
> 
>  static int safexcel_pci_probe(struct pci_dev *pdev,
> @@ -1789,54 +1786,32 @@ static struct pci_driver safexcel_pci_driver = {
>  	.probe         = safexcel_pci_probe,
>  	.remove        = safexcel_pci_remove,
>  };
> -#endif
> -
> -/* Unfortunately, we have to resort to global variables here */
> -#if IS_ENABLED(CONFIG_PCI)
> -int pcireg_rc = -EINVAL; /* Default safe value */
> -#endif
> -#if IS_ENABLED(CONFIG_OF)
> -int ofreg_rc = -EINVAL; /* Default safe value */
> -#endif
> 
>  static int __init safexcel_init(void)
>  {
> -#if IS_ENABLED(CONFIG_PCI)
> +	int ret;
> +
>  	/* 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 ...

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).

> +		ret = platform_driver_register(&crypto_safexcel);
> +		if (ret)
> +			pci_unregister_driver(&safexcel_pci_driver);
> +	}
> +
> +	return ret;
>  }
> 
>  static void __exit safexcel_exit(void)
>  {
> -#if IS_ENABLED(CONFIG_OF)
>  	/* Unregister platform driver */
> -	if (!ofreg_rc)
> +	if (IS_ENABLED(CONFIG_OF))
>  		platform_driver_unregister(&crypto_safexcel);
> -#endif
> 
> -#if IS_ENABLED(CONFIG_PCI)
>  	/* Unregister PCI driver if successfully registered before */
> -	if (!pcireg_rc)
> -		pci_unregister_driver(&safexcel_pci_driver);
> -#endif
> +	pci_unregister_driver(&safexcel_pci_driver);
>  }
> 
>  module_init(safexcel_init);
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index f9088c89a534..1a6cf19eac2d 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1686,6 +1686,7 @@ static inline struct pci_dev *pci_get_class(unsigned int class,
>  static inline void pci_set_master(struct pci_dev *dev) { }
>  static inline int pci_enable_device(struct pci_dev *dev) { return -EIO; }
>  static inline void pci_disable_device(struct pci_dev *dev) { }
> +static inline int pcim_enable_device(struct pci_dev *pdev) { return -EIO; }
>  static inline int pci_assign_resource(struct pci_dev *dev, int i)
>  { return -EBUSY; }
>  static inline int __pci_register_driver(struct pci_driver *drv,
> --
> 2.20.0

Regards,
Pascal van Leeuwen
Silicon IP Architect, Multi-Protocol Engines @ Verimatrix
www.insidesecure.com