Add comment describing ioctl number duplication

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/lttng-abi.h b/lttng-abi.h
index e23393ff9e0a28b183f1c143dbfc2f9a1b7256c6..9b9a2323b66f20f26eb498027f0e507728e5cc2b 100644 (file)
--- a/lttng-abi.h
+++ b/lttng-abi.h
@@ -197,6 +197,11 @@ struct lttng_kernel_filter_bytecode {
        _IOR(0xF6, 0x58, int32_t)
 #define LTTNG_KERNEL_SESSION_UNTRACK_PID       \
        _IOR(0xF6, 0x59, int32_t)
+/*
+ * ioctl 0x58 and 0x59 are duplicated here. It works, since _IOR vs _IO
+ * are generating two different ioctl numbers, but this was not done on
+ * purpose. We should generally try to avoid those duplications.
+ */
 #define LTTNG_KERNEL_SESSION_LIST_TRACKER_PIDS _IO(0xF6, 0x58)
 #define LTTNG_KERNEL_SESSION_METADATA_REGEN    _IO(0xF6, 0x59)