exec: introduce endianness swapped mmio

The way we're currently modeling mmio is too simplified. We assume that
every device has the same endianness as the target CPU. In reality,
most devices are little endian (all PCI and ISA ones I'm aware of). Some
are big endian (special system devices) and a very little fraction is
target native endian (fw_cfg).

So instead of assuming every device to be native endianness, let's move
to a model where the device tells us which endianness it's in.

That way we can compile the devices only once and get rid of all the ugly
swap will be done by the underlying layer.

For the same of readability, this patch only introduces the helper framework
but doesn't allow the registering code to set its endianness yet.

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>

1 files changed, 7 insertions, 1 deletions

diff --git a/cpu-common.h b/cpu-common.h
index bb6b137e16..6d4a898ad1 100644
--- a/cpu-common.h
+++ b/cpu-common.h
@@ -20,6 +20,12 @@
 
 #if !defined(CONFIG_USER_ONLY)
 
+enum device_endian {
+    DEVICE_NATIVE_ENDIAN,
+    DEVICE_BIG_ENDIAN,
+    DEVICE_LITTLE_ENDIAN,
+};
+
 /* address in the RAM (different from a physical address) */
 typedef unsigned long ram_addr_t;
 
@@ -55,7 +61,7 @@ ram_addr_t qemu_ram_addr_from_host_nofail(void *ptr);
 
 int cpu_register_io_memory(CPUReadMemoryFunc * const *mem_read,
                            CPUWriteMemoryFunc * const *mem_write,
-                           void *opaque);
+                           void *opaque, enum device_endian endian);
 void cpu_unregister_io_memory(int table_address);
 
 void cpu_physical_memory_rw(target_phys_addr_t addr, uint8_t *buf,