memory: Provide memory_region_init_rom()

Provide a new helper function memory_region_init_rom() for memory
regions which are read-only (and unlike those created by
memory_region_init_rom_device() don't have special behaviour
for writes). This has the same behaviour as calling
memory_region_init_ram() and then memory_region_set_readonly()
(which is what we do today in boards with pure ROMs) but is a
more easily discoverable API for the purpose.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1467122287-24974-2-git-send-email-peter.maydell@linaro.org

1 files changed, 7 insertions, 2 deletions

diff --git a/docs/memory.txt b/docs/memory.txt
index 431d9ca88f..811b1bd3c5 100644
--- a/docs/memory.txt
+++ b/docs/memory.txt
@@ -41,8 +41,13 @@ MemoryRegion):
   MemoryRegionOps structure describing the callbacks.
 
 - ROM: a ROM memory region works like RAM for reads (directly accessing
-  a region of host memory), but like MMIO for writes (invoking a callback).
-  You initialize these with memory_region_init_rom_device().
+  a region of host memory), and forbids writes. You initialize these with
+  memory_region_init_rom().
+
+- ROM device: a ROM device memory region works like RAM for reads
+  (directly accessing a region of host memory), but like MMIO for
+  writes (invoking a callback).  You initialize these with
+  memory_region_init_rom_device().
 
 - IOMMU region: an IOMMU region translates addresses of accesses made to it
   and forwards them to some other target memory region.  As the name suggests,