ARM: io: add a default IO_SPACE_LIMIT definition
Add a default IO_SPACE_LIMIT definition. Explain the chosen value and
suggest why platforms would want to make it larger.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/include/asm/io.h b/arch/arm/include/asm/io.h
index d66605d..ffb089d 100644
--- a/arch/arm/include/asm/io.h
+++ b/arch/arm/include/asm/io.h
@@ -110,6 +110,27 @@
#include <mach/io.h>
/*
+ * This is the limit of PC card/PCI/ISA IO space, which is by default
+ * 64K if we have PC card, PCI or ISA support. Otherwise, default to
+ * zero to prevent ISA/PCI drivers claiming IO space (and potentially
+ * oopsing.)
+ *
+ * Only set this larger if you really need inb() et.al. to operate over
+ * a larger address space. Note that SOC_COMMON ioremaps each sockets
+ * IO space area, and so inb() et.al. must be defined to operate as per
+ * readb() et.al. on such platforms.
+ */
+#ifndef IO_SPACE_LIMIT
+#if defined(CONFIG_PCMCIA_SOC_COMMON) || defined(CONFIG_PCMCIA_SOC_COMMON_MODULE)
+#define IO_SPACE_LIMIT ((resource_size_t)0xffffffff)
+#elif defined(CONFIG_PCI) || defined(CONFIG_ISA) || defined(CONFIG_PCCARD)
+#define IO_SPACE_LIMIT ((resource_size_t)0xffff)
+#else
+#define IO_SPACE_LIMIT ((resource_size_t)0)
+#endif
+#endif
+
+/*
* IO port access primitives
* -------------------------
*