On Thu, Nov 20, 2014 at 3:26 PM, Bjorn Helgaas [off-list ref] wrote:

On Wed, Nov 19, 2014 at 05:19:20PM +0100, Arnd Bergmann wrote:

quoted

On Wednesday 19 November 2014 17:04:51 Tomasz Nowicki wrote:

quoted

+/*
+ * raw_pci_read/write - ACPI PCI config space accessors.
+ *
+ * ACPI spec defines MMCFG as the way we can access PCI config space,
+ * so let MMCFG be default (__weak).
+ *
+ * If platform needs more fancy stuff, should provides its own implementation.
+ */
+int __weak raw_pci_read(unsigned int domain, unsigned int bus,
+                       unsigned int devfn, int reg, int len, u32 *val)
+{
+       return pci_mmcfg_read(domain, bus, devfn, reg, len, val);
+}
+
+int __weak raw_pci_write(unsigned int domain, unsigned int bus,
+                        unsigned int devfn, int reg, int len, u32 val)
+{
+       return pci_mmcfg_write(domain, bus, devfn, reg, len, val);
+}
+

I think it would be better to avoid __weak functions here, as they tend
to be hard to follow when trying to understand the code.

That's interesting.  I would have said exactly the opposite -- I think the
extra Kconfiggery is harder to follow than weak/strong functions :)

But consistency is better than my personal opinion.  Is there a consensus
that we should use the Kconfig strategy instead of __weak?

I too find weak/strong functions easier to follow than "Kconfiggery" (nice term
invention there).

quoted

How about using a Kconfig symbol like this:

#ifdef CONFIG_ARCH_RAW_PCI_READWRITE
int raw_pci_read(unsigned int domain, unsigned int bus, unsigned int devfn,
                 int reg, int len, u32 *val);
int raw_pci_write(unsigned int domain, unsigned int bus, unsigned int devfn,
                  int reg, int len, u32 val);
#else
static inline int raw_pci_read(unsigned int domain, unsigned int bus,
                             unsigned int devfn, int reg, int len, u32 *val)
{
      return pci_mmcfg_read(domain, bus, devfn, reg, len, val);
}

static inline int raw_pci_write(unsigned int domain, unsigned int bus,
                                      unsigned int devfn, int reg, int len, u32 val)
{
       return pci_mmcfg_write(domain, bus, devfn, reg, len, val);
}
#endif

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