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-rw-r--r--include/linux/rfkill.h14
1 files changed, 14 insertions, 0 deletions
diff --git a/include/linux/rfkill.h b/include/linux/rfkill.h
index 278777fa8a3a..10202903141a 100644
--- a/include/linux/rfkill.h
+++ b/include/linux/rfkill.h
@@ -82,6 +82,20 @@ struct rfkill_event {
__u8 soft, hard;
} __packed;
+/*
+ * We are planning to be backward and forward compatible with changes
+ * to the event struct, by adding new, optional, members at the end.
+ * When reading an event (whether the kernel from userspace or vice
+ * versa) we need to accept anything that's at least as large as the
+ * version 1 event size, but might be able to accept other sizes in
+ * the future.
+ *
+ * One exception is the kernel -- we already have two event sizes in
+ * that we've made the 'hard' member optional since our only option
+ * is to ignore it anyway.
+ */
+#define RFKILL_EVENT_SIZE_V1 8
+
/* ioctl for turning off rfkill-input (if present) */
#define RFKILL_IOC_MAGIC 'R'
#define RFKILL_IOC_NOINPUT 1