From: Alan Cox <alan@linux.intel.com>
Date: Wed, 14 Sep 2016 12:30:53 +0000 (+0100)
Subject: CPU: notes on CPU defines etc
X-Git-Url: https://git.ndcode.org/public/gitweb.cgi?a=commitdiff_plain;h=225ab1adc3063a70d6046bf6330ac9a879a6ffff;p=FUZIX.git

CPU: notes on CPU defines etc
---

diff --git a/Kernel/CPU b/Kernel/CPU
new file mode 100644
index 00000000..3b547ea4
--- /dev/null
+++ b/Kernel/CPU
@@ -0,0 +1,94 @@
+Each CPU has its own cpu subdirectory
+
+	cpu-$name/
+
+In that should be
+
+cpu.h
+	Types and definitions specific to the processor
+
+rules.mk
+	Cross compiler options and settings
+
+image.mk
+	General rules to build the final binary image
+
+
+The following other per CPU files currently have leaked outside of the CPU
+directory and will eventually move
+
+lowlevel-$cpu.[sS]
+	Low level function implementations that are common across all
+platforms using that processor type
+
+usermem_std-$cpu.[sS]
+	Standard implementation of user/kernel memory access functions for
+this processor type (may be blank)
+
+kernel-$cpu.def
+	Assembler constants and the like used to access structure offsets
+shared between the C and assembler code.
+
+
+Other CPU specific files can be placed in the cpu directory and referenced
+as needed. The lowlevel code can also be C or assembler as best suits that
+platform.
+
+
+Types and definitions: cpu.h
+
+The following standard types should be provided, either directly from a
+compiler header or in cpu.h
+
+	uint32_t
+	int32_t
+	uint16_t
+	int16_t
+	uint8_t
+	int8_t
+	size_t
+
+The following additional types are used by FUZIX
+
+	arg_t		-	a syscall argument (signed)
+	uarg_t		-	a syscall argument (unsigned)
+	usize_t		-	size_t for a userspace pointer
+	susize_t	-	ditto, signed
+	uaddr_t		-	a userspace address
+	uptr_t		-	the size of a userspace pointer
+
+	irqflags_t	-	a suitable type to hold the IRQ status
+
+	clock_t		-	used for times()
+
+	time_t		-	holds unix time split into a high/low part
+				according to byte order. Not the same as
+				user space.
+
+	ticks_t		-	clock_t with a 16bit low/high split in
+				CPU byte order
+
+Althouh not tested the uptr_t type is there to support mixed pointer size
+kernel/user space. To allow for this ugetp and uputp should be defined to
+the correct uget/put size for a pointer (or provided)
+
+EMAGIC			-	16bit platforms only (magic numbers)
+EMAGIC_2		-	define as EMAGIC if only one
+
+
+staticfast		-	define as blank unless you have a CPU that
+				is much happier accessing memory from fixed
+				addresses. Intended to make the Z80 port
+				a bit tighter
+
+
+POINTER32		-	set if pointers are 32bit
+
+used(x)			-	indicate to the compiler that x is used
+
+BIG_ENDIAN		-	set for big endian processor
+
+
+Some of the other defines currently present are obsolete including the
+banking ones and __fastcall__
+