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[v5,2/4] docs: clarify trace2 version invariants

Message ID a757bca8f99bad57806bfdcd67ac1c1f6cc38584.1570225500.git.steadmon@google.com (mailing list archive)
State New, archived
Headers show
Series trace2: discard new traces if the target directory contains too many files | expand

Commit Message

Josh Steadmon Oct. 4, 2019, 10:08 p.m. UTC 
Make it explicit that we always want trace2 "version" events to be the
first event of any trace session. Also list the changes that would or
would not cause the EVENT format version field to be incremented.

Change-Id: I20b9ac1fa0786bcaad7e290cc805cbf45b323021
Signed-off-by: Josh Steadmon <steadmon@google.com>
---
 Documentation/technical/api-trace2.txt | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)
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Patch

diff --git a/Documentation/technical/api-trace2.txt b/Documentation/technical/api-trace2.txt
index 80ffceada0..18b79128fd 100644
--- a/Documentation/technical/api-trace2.txt
+++ b/Documentation/technical/api-trace2.txt
@@ -604,7 +604,13 @@  only present on the "start" and "atexit" events.
 ==== Event-Specific Key/Value Pairs
 
 `"version"`::
-	This event gives the version of the executable and the EVENT format.
+	This event gives the version of the executable and the EVENT format. It
+	should always be the first event in a trace session. The EVENT format
+	version will be incremented if new event types are added, if existing
+	fields are removed, or if there are significant changes in
+	interpretation of existing events or fields. Smaller changes, such as
+	adding a new field to an existing event, will not require an increment
+	to the EVENT format version.
 +
 ------------
 {