[PATCH v7 04/31] docs/dyndbg: explain flags parse 1st

[Jim Cromie <jim.cromie@gmail.com>]

When writing queries to >control, flags are parsed 1st, since they are
the only required field, and they require specific compositions.  So
if the flags draw an error (on those specifics), then keyword errors
aren't reported.  This can be mildly confusing/annoying, so explain it
instead.

cc: linux-doc@vger.kernel.org
Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
 .../admin-guide/dynamic-debug-howto.rst         | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/Documentation/admin-guide/dynamic-debug-howto.rst b/Documentation/admin-guide/dynamic-debug-howto.rst
index 4ac18c0a1d95..e76ccd987704 100644
--- a/Documentation/admin-guide/dynamic-debug-howto.rst
+++ b/Documentation/admin-guide/dynamic-debug-howto.rst
@@ -109,10 +109,19 @@ The match-spec's select *prdbgs* from the catalog, upon which to apply
 the flags-spec, all constraints are ANDed together.  An absent keyword
 is the same as keyword "*".
 
-
-A match specification is a keyword, which selects the attribute of
-the callsite to be compared, and a value to compare against.  Possible
-keywords are:::
+Note that since the match-spec can be empty, the flags are checked 1st,
+then the pairs of keyword and value.  Flag errs will hide keyword errs::
+
+  bash-5.2# ddcmd mod bar +foo
+  dyndbg: read 13 bytes from userspace
+  dyndbg: query 0: "mod bar +foo" mod:*
+  dyndbg: unknown flag 'o'
+  dyndbg: flags parse failed
+  dyndbg: processed 1 queries, with 0 matches, 1 errs
+
+So a match-spec is a keyword, which selects the attribute of the
+callsite to be compared, and a value to compare against.  Possible
+keywords are::
 
   match-spec ::= 'func' string |
 		 'file' string |
-- 
2.52.0