Add READ_ONLY flag to indicate access type to allocated host memory (#454)

* Add READ_ONLY flag to indicate access type to allocated host memory

allows mapping host memory as read-only on device when zeMemAllocHost()
is used with external memmap sysmem.

Signed-off-by: Mateusz Hoppe <mateusz.hoppe@intel.com>

Author: HoppeMateusz

scripts/core/EXT_ExternalMemMap.rst

@@ -32,4 +32,5 @@ Mapping External Memory to Host Allocation
 
 Accelerator devices can map external memory as a host allocation. The ${x}_external_memmap_sysmem_ext_desc_t struct defines the system memory being mapped as part of the ${x}MemAllocHost.
 The user may use this extention to specify, as part of the pNext member of the ${x}_host_mem_alloc_desc_t , the system memory that needs to be mapped as part of the allocation being created with a call to ${x}MemAllocHost.
+For read-only system memory $(X}_HOST_MEM_ALLOC_FLAG_MEM_READ_ONLY flag should be set in ${x}_host_mem_alloc_desc_t.
 

scripts/core/memory.yml

@@ -56,6 +56,9 @@ etors:
     - name: BIAS_INITIAL_PLACEMENT
       desc: "optimize shared allocation for first access on the host"
       version: "1.2"
+    - name: MEM_READ_ONLY
+      desc: "device access will be read-only, mutually exclusive with $X_HOST_MEM_ALLOC_FLAG_BIAS_WRITE_COMBINED"
+      version: "1.16"
 --- #--------------------------------------------------------------------------
 type: struct
 desc: "Host memory allocation descriptor"