Require trace byte_order field, remove use of magic number for autodetection

[ctf.git] / common-trace-format-proposal.txt

diff --git a/common-trace-format-proposal.txt b/common-trace-format-proposal.txt
index f8ddcacc2811867dbcc2fdd9b99ed4d80bed9dca..7f978306bd44eeb91ca40136a1c20c8a5f803324 100644 (file)
--- a/common-trace-format-proposal.txt
+++ b/common-trace-format-proposal.txt
@@ -530,14 +530,10 @@ the metadata.
 
 Fixed layout (event packet header):
 
-- Magic number (CTF magic numbers: 0xC1FC1FC1 and its reverse endianness
-  representation: 0xC11FFCC1) It needs to have a non-symmetric bytewise
-  representation. Used to distinguish between big and little endian traces (this
-  information is determined by knowing the endianness of the architecture
-  reading the trace and comparing the magic number against its value and the
-  reverse, 0xC11FFCC1). This magic number specifies that we use the CTF metadata
-  description language described in this document. Different magic numbers
-  should be used for other metadata description languages.
+- Magic number (CTF magic number: 0xC1FC1FC1 This magic number specifies
+  that we use the CTF metadata description language described in this
+  document. Different magic numbers should be used for other metadata
+  description languages.
 - Trace UUID, used to ensure the event packet match the metadata used.
   (note: we cannot use a metadata checksum because metadata can be appended to
    while tracing is active)
@@ -597,9 +593,6 @@ trace {
   packet.header := struct event_packet_header;
 };
 
-If a packet header lacks the "magic" number field, the trace endianness
-needs to be specified in the trace "byte_order" metadata attribute.
-
 If the trace_uuid is not present, no validation that the metadata
 actually corresponds to the stream is performed.
 
@@ -902,10 +895,6 @@ The grammar representing the TSDL metadata is presented in Appendix C.
 TSDL Grammar. This section presents a rather ligher reading that
 consists in examples of TSDL metadata, with template values.
 
-Note that the trace endianness is usually extracted from the packet
-header magic number. The "byte_order" field is only needed when the magic
-number packet header field is not present.
-
 The stream "id" can be left out if there is only one stream in the
 trace. The event "id" field can be left out if there is only one event
 in a stream.
@@ -914,7 +903,7 @@ trace {
   major = value;                               /* Trace format version */
   minor = value;
   uuid = "aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa";       /* Trace UUID */
-  byte_order = be OR le;                       /* Endianness (optional) */
+  byte_order = be OR le;                       /* Endianness (required) */
   packet.header := struct {
     uint32_t magic;
     uint8_t  trace_uuid[16];