PCI: create common pcibios_err_to_errno

For returning errors out to non-PCI code.  Re-name xen's version.

Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

include/linux/pci.h

@@ -474,6 +474,32 @@ static inline bool pci_dev_msi_enabled(struct pci_dev *pci_dev) { return false;
 #define PCIBIOS_SET_FAILED		0x88
 #define PCIBIOS_BUFFER_TOO_SMALL	0x89
 
+/*
+ * Translate above to generic errno for passing back through non-pci.
+ */
+static inline int pcibios_err_to_errno(int err)
+{
+	if (err <= PCIBIOS_SUCCESSFUL)
+		return err; /* Assume already errno */
+
+	switch (err) {
+	case PCIBIOS_FUNC_NOT_SUPPORTED:
+		return -ENOENT;
+	case PCIBIOS_BAD_VENDOR_ID:
+		return -EINVAL;
+	case PCIBIOS_DEVICE_NOT_FOUND:
+		return -ENODEV;
+	case PCIBIOS_BAD_REGISTER_NUMBER:
+		return -EFAULT;
+	case PCIBIOS_SET_FAILED:
+		return -EIO;
+	case PCIBIOS_BUFFER_TOO_SMALL:
+		return -ENOSPC;
+	}
+
+	return -ENOTTY;
+}
+
 /* Low-level architecture-dependent routines */
 
 struct pci_ops {