@@ -390,42 +390,56 @@ in case ``prefix_str`` is built dynamically.
Dynamic Debug classmaps
=======================
-Dyndbg allows selection/grouping of *prdbg* callsites using structural
-info: module, file, function, line. Classmaps allow authors to add
-their own domain-oriented groupings using class-names. Classmaps are
-exported, so they referencable from other modules.
+Classmaps adds the "class" keyword, which selects prdbgs based on
+author supplied, domain-oriented names; this complements the code
+organizational keywords: module, file, function, line.
+
+The main difference from the others: class'd prdbgs must be named to
+be changed. This protects them from generic overwrite:
+
+ # IOW this cannot undo any DRM.debug settings
+ :#> ddcmd -p
+
+So each class must be enabled individually (no wildcards):
- # enable classes individually
:#> ddcmd class DRM_UT_CORE +p
:#> ddcmd class DRM_UT_KMS +p
# or more selectively
:#> ddcmd class DRM_UT_CORE module drm +p
-The "class FOO" syntax protects class'd prdbgs from generic overwrite::
-
- # IOW this doesn't wipe any DRM.debug settings
- :#> ddcmd -p
+Or the legacy/normal (convenient) way:
-To support the DRM.debug parameter, DYNDBG_CLASSMAP_PARAM* updates all
-classes in a classmap, mapping param-bits 0..N onto the classes:
-DRM_UT_<*> for the DRM use-case.
+ :#> echo 0x1ff > /sys/module/drm/parameters/debug
Dynamic Debug Classmap API
==========================
-DYNDBG_CLASSMAP_DEFINE - modules use this to create classmaps, naming
-each of the classes (stringified enum-symbols: "DRM_UT_<*>"), and
-type, and mapping the class-names to consecutive _class_ids.
+The classmap API is closely modeled on DRM, which has:
+
+enum drm_debug_category: DRM_UT_* // 10 independent categories.
+dyndbg's .classid encodes that directly, allowing 0..62 classes
+
+DRM has ~5k calls like: drm_dbg(DRM_UT_KMS, "kms msg");
+these are unchanged, even in argtype, since classid === category.
+
+DRM controls the classes together via sysfs; bits 0..9 control the
+classes independently.
+
+Its expected that other classmap users will also provide debug-macros
+using an enum-defined categorization scheme like DRM's, and dyndbg can
+be adapted under them similarly.
+
+DYNDBG_CLASSMAP_DEFINE(var,type,_base,classnames) - this maps
+classnames onto class-ids starting at _base, it also maps the
+names onto CLASSMAP_PARAM bits 0..N.
-By doing so, modules tell dyndbg that they have prdbgs with those
-class_ids, and they authorize dyndbg to accept "class FOO" for the
-module defining the classmap, and its contained classnames.
+DYNDBG_CLASSMAP_USE(var) - modules call this to refer to the var
+_DEFINEd elsewhere (and exported).
-DYNDBG_CLASSMAP_USE - drm drivers invoke this to ref the CLASSMAP that
-drm DEFINEs. This shares the classmap definition, and authorizes
-dyndbg to apply changes to the user module's class'd pr_debugs. It
-also tells dyndbg how to initialize the user's prdbgs at modprobe,
-based upon the current setting of the parent's controlling param.
+Classmaps are opt-in: modules invoke _DEFINE or _USE to authorize
+dyndbg to update those classes. "class FOO" queries are validated
+against the classes, this finds the classid to alter; classes are not
+directly selectable by their classid.
There are 2 types of classmaps:
@@ -436,9 +450,9 @@ DYNDBG_CLASSMAP_PARAM - modelled after module_param_cb, it refers to a
DEFINEd classmap, and associates it to the param's data-store. This
state is then applied to DEFINEr and USEr modules when they're modprobed.
-This interface also enforces the DD_CLASS_TYPE_LEVEL_NUM relation
+The PARAM interface also enforces the DD_CLASS_TYPE_LEVEL_NUM relation
amongst the contained classnames; all classes are independent in the
-control parser itself.
+control parser itself; there is no implied meaning in names like "V4".
Modules or module-groups (drm & drivers) can define multiple
classmaps, as long as they share the limited 0..62 per-module-group
reword the classmaps-api section to better explain how it supports DRM, and (a little bit) to steer clear of designated-inits in the _DEFINE description. probably just squash this back in Signed-off-by: Jim Cromie <jim.cromie@gmail.com> --- .../admin-guide/dynamic-debug-howto.rst | 64 +++++++++++-------- 1 file changed, 39 insertions(+), 25 deletions(-)