Add an IOCTL to check ION ABI version

Userspace needs a way to detect ION ABI version at runtime to determine
heap IDs. CURRENT_ION_ABI_VERSION is set to 2 considering legacy and
upstream versions as 0 and 1.

Bug: 140916230
Test: make

Signed-off-by: Hridya Valsaraju <hridya@google.com>

Change-Id: Ie9d9e23c2d8323620832906d33745d599cbce6be

drivers/staging/android/ion/ion.c

@@ -27,6 +27,8 @@
 
 #include "ion_private.h"
 
+#define ION_CURRENT_ABI_VERSION  2
+
 static struct ion_device *internal_dev;
 
 /* Entry into ION allocator for rest of the kernel */
@@ -108,6 +110,7 @@ out:
 union ion_ioctl_arg {
 	struct ion_allocation_data allocation;
 	struct ion_heap_query query;
+	u32 ion_abi_version;
 };
 
 static int validate_ioctl_arg(unsigned int cmd, union ion_ioctl_arg *arg)
@@ -169,6 +172,9 @@ static long ion_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 	case ION_IOC_HEAP_QUERY:
 		ret = ion_query_heaps(&data.query);
 		break;
+	case ION_IOC_ABI_VERSION:
+		data.ion_abi_version = ION_CURRENT_ABI_VERSION;
+		break;
 	default:
 		return -ENOTTY;
 	}

include/uapi/linux/ion.h

@@ -159,4 +159,11 @@ struct ion_heap_query {
 #define ION_IOC_HEAP_QUERY     _IOWR(ION_IOC_MAGIC, 8, \
 					struct ion_heap_query)
 
+/**
+ * DOC: ION_IOC_HEAP_ABI_VERSION - return ABI version
+ *
+ * Returns ABI version for this driver
+ */
+#define ION_IOC_ABI_VERSION    _IOR(ION_IOC_MAGIC, 9, \
+					__u32)
 #endif /* _UAPI_LINUX_ION_H */