linux-kernel - [PATCH v7 01/25] test-dyndbg: fixup CLASSMAP usage error

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Message-ID: <20231012172137.3286566-2-jim.cromie@gmail.com>
Date:   Thu, 12 Oct 2023 11:21:12 -0600
From:   Jim Cromie <jim.cromie@...il.com>
To:     linux-kernel@...r.kernel.org, jbaron@...mai.com,
        gregkh@...uxfoundation.org, dri-devel@...ts.freedesktop.org,
        amd-gfx@...ts.freedesktop.org, intel-gvt-dev@...ts.freedesktop.org,
        intel-gfx@...ts.freedesktop.org
Cc:     daniel.vetter@...ll.ch, jani.nikula@...el.com,
        ville.syrjala@...ux.intel.com, seanpaul@...omium.org,
        robdclark@...il.com, groeck@...gle.com, yanivt@...gle.com,
        bleung@...gle.com, linux-doc@...r.kernel.org,
        Jim Cromie <jim.cromie@...il.com>
Subject: [PATCH v7 01/25] test-dyndbg: fixup CLASSMAP usage error

more careful reading of test output reveals:

lib/test_dynamic_debug.c:103 [test_dynamic_debug]do_cats =pmf "doing categories\n"
lib/test_dynamic_debug.c:105 [test_dynamic_debug]do_cats =p "LOW msg\n" class:MID
lib/test_dynamic_debug.c:106 [test_dynamic_debug]do_cats =p "MID msg\n" class:HI
lib/test_dynamic_debug.c:107 [test_dynamic_debug]do_cats =_ "HI msg\n" class unknown, _id:13

That last line is wrong, the HI class is declared.

But the enum's 1st val (explicitly initialized) was wrong; it must be
_base, not _base+1 (a DECLARE_DYNDBG_CLASSMAP[1] param).  So the last
enumeration exceeded the range of mapped class-id's, which triggered
the "class unknown" report.  I intentionally coded in an error, but
forgot to verify its detection and remove it.

RFC:

This patch fixes a bad usage of DECLARE_DYNDBG_CLASSMAP(), showing
that it is too error-prone.  As noted in test-mod comments:

 * Using the CLASSMAP api:
 * - classmaps must have corresponding enum
 * - enum symbols must match/correlate with class-name strings in the map.
 * - base must equal enum's 1st value
 * - multiple maps must set their base to share the 0-62 class_id space !!
 *   (build-bug-on tips welcome)

Those shortcomings could largely be fixed with a __stringify_list
(which doesn't exist,) used in DECLARE_DYNDBG_CLASSMAP to stringify
__VA_ARGS__.  Then, API would accept DRM_UT_* values literally; all
the categories, in order, and not their stringifications, which
created all the usage complications above.

[1] name changes later to DYNDBG_CLASSMAP_DEFINE

Signed-off-by: Jim Cromie <jim.cromie@...il.com>
---
 lib/test_dynamic_debug.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/test_dynamic_debug.c b/lib/test_dynamic_debug.c
index 8dd250ad022b..a01f0193a419 100644
--- a/lib/test_dynamic_debug.c
+++ b/lib/test_dynamic_debug.c
@@ -75,7 +75,7 @@ DD_SYS_WRAP(disjoint_bits, p);
 DD_SYS_WRAP(disjoint_bits, T);

 /* symbolic input, independent bits */
-enum cat_disjoint_names { LOW = 11, MID, HI };
+enum cat_disjoint_names { LOW = 10, MID, HI };
 DECLARE_DYNDBG_CLASSMAP(map_disjoint_names, DD_CLASS_TYPE_DISJOINT_NAMES, 10,
 			"LOW", "MID", "HI");
 DD_SYS_WRAP(disjoint_names, p);
-- 
2.41.0