From 2e634ba4191594394d9b378eed7850b2242d9cb4 Mon Sep 17 00:00:00 2001
From: Brendan King <Brendan.King@imgtec.com>
Date: Tue, 13 Jun 2017 15:52:44 +0100
Subject: [PATCH 1/3] libsync: add support for pre-v4.7 kernels

Add support for the the sync merge ioctl supported by older kernels.
---
 libsync.h | 44 +++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 41 insertions(+), 3 deletions(-)

diff --git a/libsync.h b/libsync.h
index f1a2f96d..c3b8a385 100644
--- a/libsync.h
+++ b/libsync.h
@@ -40,6 +40,10 @@
 extern "C" {
 #endif
 
+#ifndef SYNC_IOC_MAGIC
+#define SYNC_IOC_MAGIC		'>'
+#endif
+
 #ifndef SYNC_IOC_MERGE
 /* duplicated from linux/sync_file.h to avoid build-time dependency
  * on new (v4.7) kernel headers.  Once distro's are mostly using
@@ -53,10 +57,22 @@ struct sync_merge_data {
 	uint32_t	flags;
 	uint32_t	pad;
 };
-#define SYNC_IOC_MAGIC		'>'
 #define SYNC_IOC_MERGE		_IOWR(SYNC_IOC_MAGIC, 3, struct sync_merge_data)
 #endif
 
+#ifndef SYNC_IOC_LEGACY_MERGE
+/* the legacy definitions are based on the contents of
+ * drivers/staging/android/uapi/sync.h in the v4.4 kernel.
+ */
+struct sync_legacy_merge_data {
+	int32_t	fd2;
+	char	name[32];
+	int32_t	fence;
+};
+
+#define SYNC_IOC_LEGACY_MERGE	_IOWR(SYNC_IOC_MAGIC, 1, \
+	struct sync_legacy_merge_data)
+#endif
 
 static inline int sync_wait(int fd, int timeout)
 {
@@ -83,6 +99,24 @@ static inline int sync_wait(int fd, int timeout)
 	return ret;
 }
 
+static inline int sync_legacy_merge(const char *name, int fd1, int fd2)
+{
+	struct sync_legacy_merge_data data;
+	int ret;
+
+	data.fd2 = fd2;
+	strncpy(data.name, name, sizeof(data.name));
+
+	do {
+		ret = ioctl(fd1, SYNC_IOC_LEGACY_MERGE, &data);
+	} while (ret == -1 && (errno == EINTR || errno == EAGAIN));
+
+	if (ret < 0)
+		return ret;
+
+	return data.fence;
+}
+
 static inline int sync_merge(const char *name, int fd1, int fd2)
 {
 	struct sync_merge_data data = {0};
@@ -95,8 +129,12 @@ static inline int sync_merge(const char *name, int fd1, int fd2)
 		ret = ioctl(fd1, SYNC_IOC_MERGE, &data);
 	} while (ret == -1 && (errno == EINTR || errno == EAGAIN));
 
-	if (ret < 0)
-		return ret;
+	if (ret < 0) {
+		if (errno == ENOTTY)
+			return sync_legacy_merge(name, fd1, fd2);
+		else
+			return ret;
+	}
 
 	return data.fence;
 }
-- 
2.25.1