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@xxxxxxxxx> --- .../admin-guide/dynamic-debug-howto.rst | 64 +++++++++++-------- 1 file changed, 39 insertions(+), 25 deletions(-) diff --git a/Documentation/admin-guide/dynamic-debug-howto.rst b/Documentation/admin-guide/dynamic-debug-howto.rst index ccf3704f2143..1ffab6be07fc 100644 --- a/Documentation/admin-guide/dynamic-debug-howto.rst +++ b/Documentation/admin-guide/dynamic-debug-howto.rst @@ -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 -- 2.45.2 _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
