[PATCH v2 3/4] x86/iosf: Make IOSF driver modular and usable by more drivers

["David E. Box" <david.e.box@linux.intel.com>]

From: "David E. Box" <david.e.box@linux.intel.com>

Currently drivers that work on big core can't use the mailbox driver without
selecting it which forces an unneeded dependency. Provides dummy fucntions to
allow these modules to conditionally use the mailbox on soc's without limiting
their ability to compile and load on big core systems. Make mailbox driver
build default m to ensure availability on x86 SOC's.

Signed-off-by: David E. Box <david.e.box@linux.intel.com>
---
 arch/x86/Kconfig                |    7 ++-----
 arch/x86/include/asm/iosf_mbi.h |   33 +++++++++++++++++++++++++++++++++
 arch/x86/kernel/iosf_mbi.c      |    6 ++++++
 3 files changed, 41 insertions(+), 5 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 25d2c6f..f1304d3 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2375,12 +2375,9 @@ config X86_DMA_REMAP
 	depends on STA2X11
 
 config IOSF_MBI
-	bool
+	tristate
+	default m
 	depends on PCI
-	---help---
-	  To be selected by modules requiring access to the Intel OnChip System
-	  Fabric (IOSF) Sideband MailBox Interface (MBI). For MBI platforms
-	  enumerable by PCI.
 
 source "net/Kconfig"
 
diff --git a/arch/x86/include/asm/iosf_mbi.h b/arch/x86/include/asm/iosf_mbi.h
index 8e71c79..9e92d65 100644
--- a/arch/x86/include/asm/iosf_mbi.h
+++ b/arch/x86/include/asm/iosf_mbi.h
@@ -50,6 +50,10 @@
 #define BT_MBI_PCIE_READ	0x00
 #define BT_MBI_PCIE_WRITE	0x01
 
+#if defined(CONFIG_IOSF_MBI) || defined(CONFIG_IOSF_MBI_MODULE)
+
+bool iosf_mbi_available(void);
+
 /**
  * iosf_mbi_read() - MailBox Interface read command
  * @port:	port indicating subunit being accessed
@@ -87,4 +91,33 @@ int iosf_mbi_write(u8 port, u8 opcode, u32 offset, u32 mdr);
  */
 int iosf_mbi_modify(u8 port, u8 opcode, u32 offset, u32 mdr, u32 mask);
 
+#else /* CONFIG_IOSF_MBI is not enabled */
+static inline
+bool iosf_mbi_available(void)
+{
+	return false;
+}
+
+static inline
+int iosf_mbi_read(u8 port, u8 opcode, u32 offset, u32 *mdr)
+{
+	WARN(1, "MBI driver not available");
+	return -EPERM;
+}
+
+static inline
+int iosf_mbi_write(u8 port, u8 opcode, u32 offset, u32 mdr)
+{
+	WARN(1, "MBI driver not available");
+	return -EPERM;
+}
+
+static inline
+int iosf_mbi_modify(u8 port, u8 opcode, u32 offset, u32 mdr, u32 mask)
+{
+	WARN(1, "MBI driver not available");
+	return -EPERM;
+}
+#endif /* CONFIG_IOSF_MBI */
+
 #endif /* IOSF_MBI_SYMS_H */
diff --git a/arch/x86/kernel/iosf_mbi.c b/arch/x86/kernel/iosf_mbi.c
index c3aae66..d3803c6 100644
--- a/arch/x86/kernel/iosf_mbi.c
+++ b/arch/x86/kernel/iosf_mbi.c
@@ -177,6 +177,12 @@ int iosf_mbi_modify(u8 port, u8 opcode, u32 offset, u32 mdr, u32 mask)
 }
 EXPORT_SYMBOL(iosf_mbi_modify);
 
+bool iosf_mbi_available(void)
+{
+	return mbi_pdev;
+}
+EXPORT_SYMBOL(iosf_mbi_available);
+
 static int iosf_mbi_probe(struct pci_dev *pdev,
 			  const struct pci_device_id *unused)
 {
-- 
1.7.10.4