With all subsystems and drivers either declaring their dependence on
HAS_IOPORT or fencing I/O port specific code sections we can finally
make inb()/outb() and friends compile-time dependent on HAS_IOPORT as
suggested by Linus in the linked mail. The main benefit of this is that
on platforms such as s390 which have no meaningful way of implementing
inb()/outb() their use without the proper HAS_IOPORT dependency will
result in easy to catch and fix compile-time errors instead of compiling
code that can never work.

Link: https://lore.kernel.org/lkml/CAHk-=wg80je=K7madF4e7WrRNp37e3qh6y10Svhdc7O8SZ_-8g@mail.gmail.com/
Co-developed-by: Arnd Bergmann <arnd@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@kernel.org>
Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
---
 include/asm-generic/io.h | 60 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 60 insertions(+)

diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
index 80de699bf6af4b7b77f582c0469c43e978f67a43..1027be6a62bcbcd5f6797e0fa42035208d0ca79f 100644
--- a/include/asm-generic/io.h
+++ b/include/asm-generic/io.h
@@ -540,6 +540,7 @@ static inline void writesq(volatile void __iomem *addr, const void *buffer,
 
 #if !defined(inb) && !defined(_inb)
 #define _inb _inb
+#ifdef CONFIG_HAS_IOPORT
 static inline u8 _inb(unsigned long addr)
 {
 	u8 val;
@@ -549,10 +550,15 @@ static inline u8 _inb(unsigned long addr)
 	__io_par(val);
 	return val;
 }
+#else
+u8 _inb(unsigned long addr)
+	__compiletime_error("inb()) requires CONFIG_HAS_IOPORT");
+#endif
 #endif
 
 #if !defined(inw) && !defined(_inw)
 #define _inw _inw
+#ifdef CONFIG_HAS_IOPORT
 static inline u16 _inw(unsigned long addr)
 {
 	u16 val;
@@ -562,10 +568,15 @@ static inline u16 _inw(unsigned long addr)
 	__io_par(val);
 	return val;
 }
+#else
+u16 _inw(unsigned long addr)
+	__compiletime_error("inw() requires CONFIG_HAS_IOPORT");
+#endif
 #endif
 
 #if !defined(inl) && !defined(_inl)
 #define _inl _inl
+#ifdef CONFIG_HAS_IOPORT
 static inline u32 _inl(unsigned long addr)
 {
 	u32 val;
@@ -575,36 +586,55 @@ static inline u32 _inl(unsigned long addr)
 	__io_par(val);
 	return val;
 }
+#else
+u32 _inl(unsigned long addr)
+	__compiletime_error("inl() requires CONFIG_HAS_IOPORT");
+#endif
 #endif
 
 #if !defined(outb) && !defined(_outb)
 #define _outb _outb
+#ifdef CONFIG_HAS_IOPORT
 static inline void _outb(u8 value, unsigned long addr)
 {
 	__io_pbw();
 	__raw_writeb(value, PCI_IOBASE + addr);
 	__io_paw();
 }
+#else
+void _outb(u8 value, unsigned long addr)
+	__compiletime_error("outb() requires CONFIG_HAS_IOPORT");
+#endif
 #endif
 
 #if !defined(outw) && !defined(_outw)
 #define _outw _outw
+#ifdef CONFIG_HAS_IOPORT
 static inline void _outw(u16 value, unsigned long addr)
 {
 	__io_pbw();
 	__raw_writew((u16 __force)cpu_to_le16(value), PCI_IOBASE + addr);
 	__io_paw();
 }
+#else
+void _outw(u16 value, unsigned long addr)
+	__compiletime_error("outw() requires CONFIG_HAS_IOPORT");
+#endif
 #endif
 
 #if !defined(outl) && !defined(_outl)
 #define _outl _outl
+#ifdef CONFIG_HAS_IOPORT
 static inline void _outl(u32 value, unsigned long addr)
 {
 	__io_pbw();
 	__raw_writel((u32 __force)cpu_to_le32(value), PCI_IOBASE + addr);
 	__io_paw();
 }
+#else
+void _outl(u32 value, unsigned long addr)
+	__compiletime_error("outl() requires CONFIG_HAS_IOPORT");
+#endif
 #endif
 
 #include <linux/logic_pio.h>
@@ -688,53 +718,83 @@ static inline void outl_p(u32 value, unsigned long addr)
 
 #ifndef insb
 #define insb insb
+#ifdef CONFIG_HAS_IOPORT
 static inline void insb(unsigned long addr, void *buffer, unsigned int count)
 {
 	readsb(PCI_IOBASE + addr, buffer, count);
 }
+#else
+void insb(unsigned long addr, void *buffer, unsigned int count)
+	__compiletime_error("insb() requires HAS_IOPORT");
+#endif
 #endif
 
 #ifndef insw
 #define insw insw
+#ifdef CONFIG_HAS_IOPORT
 static inline void insw(unsigned long addr, void *buffer, unsigned int count)
 {
 	readsw(PCI_IOBASE + addr, buffer, count);
 }
+#else
+void insw(unsigned long addr, void *buffer, unsigned int count)
+	__compiletime_error("insw() requires HAS_IOPORT");
+#endif
 #endif
 
 #ifndef insl
 #define insl insl
+#ifdef CONFIG_HAS_IOPORT
 static inline void insl(unsigned long addr, void *buffer, unsigned int count)
 {
 	readsl(PCI_IOBASE + addr, buffer, count);
 }
+#else
+void insl(unsigned long addr, void *buffer, unsigned int count)
+	__compiletime_error("insl() requires HAS_IOPORT");
+#endif
 #endif
 
 #ifndef outsb
 #define outsb outsb
+#ifdef CONFIG_HAS_IOPORT
 static inline void outsb(unsigned long addr, const void *buffer,
 			 unsigned int count)
 {
 	writesb(PCI_IOBASE + addr, buffer, count);
 }
+#else
+void outsb(unsigned long addr, const void *buffer, unsigned int count)
+	__compiletime_error("outsb() requires HAS_IOPORT");
+#endif
 #endif
 
 #ifndef outsw
 #define outsw outsw
+#ifdef CONFIG_HAS_IOPORT
 static inline void outsw(unsigned long addr, const void *buffer,
 			 unsigned int count)
 {
 	writesw(PCI_IOBASE + addr, buffer, count);
 }
+#else
+void outsw(unsigned long addr, const void *buffer, unsigned int count)
+	__compiletime_error("outsw() requires HAS_IOPORT");
+#endif
 #endif
 
 #ifndef outsl
 #define outsl outsl
+#ifdef CONFIG_HAS_IOPORT
 static inline void outsl(unsigned long addr, const void *buffer,
 			 unsigned int count)
 {
 	writesl(PCI_IOBASE + addr, buffer, count);
 }
+#else
+void outsl(unsigned long addr, const void *buffer, unsigned int count)
+	__compiletime_error("outsl() requires HAS_IOPORT");
+#endif
 #endif
 
 #ifndef insb_p

-- 
2.45.2