linux-kernel - [PATCH v8-RESEND 27/33] dyndbg-doc: explain flags parse 1st

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Message-ID: <20240516174357.26755-28-jim.cromie@gmail.com>
Date: Thu, 16 May 2024 11:43:51 -0600
From: Jim Cromie <jim.cromie@...il.com>
To: jbaron@...mai.com,
	gregkh@...uxfoundation.org,
	linux-kernel@...r.kernel.org
Cc: ukaszb@...omium.org,
	linux@...musvillemoes.dk,
	joe@...ches.com,
	mcgrof@...nel.org,
	daniel.vetter@...ll.ch,
	tvrtko.ursulin@...ux.intel.com,
	jani.nikula@...el.com,
	ville.syrjala@...ux.intel.com,
	seanpaul@...omium.org,
	robdclark@...il.com,
	groeck@...gle.com,
	yanivt@...gle.com,
	bleung@...gle.com,
	Jim Cromie <jim.cromie@...il.com>
Subject: [PATCH v8-RESEND 27/33] dyndbg-doc: explain flags parse 1st

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

This note could be moved up to just after the grammar id's the flags,
and before the match-spec is detailed.  Opinions ?

Signed-off-by: Jim Cromie <jim.cromie@...il.com>
---
 Documentation/admin-guide/dynamic-debug-howto.rst | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/Documentation/admin-guide/dynamic-debug-howto.rst b/Documentation/admin-guide/dynamic-debug-howto.rst
index 7b570f29ae98..ccf3704f2143 100644
--- a/Documentation/admin-guide/dynamic-debug-howto.rst
+++ b/Documentation/admin-guide/dynamic-debug-howto.rst
@@ -106,6 +106,16 @@ 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 "*".
 
+Note: because the match-spec can be empty, the flags are checked 1st,
+then the pairs of keyword values.  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
+
 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:::
-- 
2.45.0