+ This optional function does a "fast" set of critical region protection to the
+ value specified by pval. See the documentation for sys_arch_protect() for
+ more information. This function is only required if your port is supporting
+ an operating system.
+
+-------------------------------------------------------------------------------
+Additional files required for the "OS support" emulation layer:
+-------------------------------------------------------------------------------
+
+cc.h - Architecture environment, some compiler specific, some
+ environment specific (probably should move env stuff
+ to sys_arch.h.)
+
+ Typedefs for the types used by lwip -
+ u8_t, s8_t, u16_t, s16_t, u32_t, s32_t, mem_ptr_t
+
+ Compiler hints for packing lwip's structures -
+ PACK_STRUCT_FIELD(x)
+ PACK_STRUCT_STRUCT
+ PACK_STRUCT_BEGIN
+ PACK_STRUCT_END
+
+ Platform specific diagnostic output -
+ LWIP_PLATFORM_DIAG(x) - non-fatal, print a message.
+ LWIP_PLATFORM_ASSERT(x) - fatal, print message and abandon execution.
+
+ "lightweight" synchronization mechanisms -
+ SYS_ARCH_DECL_PROTECT(x) - declare a protection state variable.
+ SYS_ARCH_PROTECT(x) - enter protection mode.
+ SYS_ARCH_UNPROTECT(x) - leave protection mode.
+
+ If the compiler does not provide memset() this file must include a
+ definition of it, or include a file which defines it.
+
+ This file must either include a system-local <errno.h> which defines
+ the standard *nix error codes, or it should #define LWIP_PROVIDE_ERRNO
+ to make lwip/arch.h define the codes which are used throughout.
+
+
+perf.h - Architecture specific performance measurement.
+ Measurement calls made throughout lwip, these can be defined to nothing.
+ PERF_START - start measuring something.
+ PERF_STOP(x) - stop measuring something, and record the result.