linux-kernel - [PATCH] pci: Add dummy for pci_acs_enabled() if CONFIG

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Date:   Mon, 11 Sep 2017 14:29:15 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Bjorn Helgaas <bhelgaas@...gle.com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Alex Williamson <alex.williamson@...hat.com>,
        Joerg Roedel <jroedel@...e.de>, linux-pci@...r.kernel.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: [PATCH] pci: Add dummy for pci_acs_enabled() if CONFIG_PCI=n to fix iommmu build

If CONFIG_PCI=n, and gcc (e.g. 4.1.2) decides not to inline
get_pci_function_alias_group(), the build fails with:

    drivers/iommu/iommu.o: In function `get_pci_function_alias_group':
    iommu.c:(.text+0xfdc): undefined reference to `pci_acs_enabled'

Due to the various dummies for PCI calls in the CONFIG_PCI=n case,
pci_acs_enabled() isn't actually ever called, but not all versions of
gcc are smart enough to realize that.

While explicitly marking get_pci_function_alias_group() inline would fix
the build, this would inflate the code for the CONFIG_PCI=y case, as
get_pci_function_alias_group() is a not-so-small function called from
two places.

Hence fix the issue by introducing a dummy for pci_acs_enabled()
instead.

Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
---
 include/linux/pci.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/linux/pci.h b/include/linux/pci.h
index f68c58a93dd045b9..f4f8ee5a7362e982 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1685,6 +1685,8 @@ static inline int pci_get_new_domain_nr(void) { return -ENOSYS; }

 #define dev_is_pci(d) (false)
 #define dev_is_pf(d) (false)
+static inline bool pci_acs_enabled(struct pci_dev *pdev, u16 acs_flags)
+{ return false; }
 #endif /* CONFIG_PCI */

 /* Include architecture-dependent settings and functions */
-- 
2.7.4