Add some basic info on classmap usage and api cc: linux-doc@xxxxxxxxxxxxxxx Signed-off-by: Jim Cromie <jim.cromie@xxxxxxxxx> --- v5- adjustments per Randy Dunlap, me v7b- checkpatch fixes --- .../admin-guide/dynamic-debug-howto.rst | 60 ++++++++++++++++++- 1 file changed, 59 insertions(+), 1 deletion(-) diff --git a/Documentation/admin-guide/dynamic-debug-howto.rst b/Documentation/admin-guide/dynamic-debug-howto.rst index 0b3d39c610d9..028c2cb5b4c5 100644 --- a/Documentation/admin-guide/dynamic-debug-howto.rst +++ b/Documentation/admin-guide/dynamic-debug-howto.rst @@ -225,7 +225,6 @@ the ``p`` flag has meaning, other flags are ignored. Note the regexp ``^[-+=][fslmpt_]+$`` matches a flags specification. To clear all flags at once, use ``=_`` or ``-fslmpt``. - Debug messages during Boot Process ================================== @@ -375,3 +374,62 @@ just a shortcut for ``print_hex_dump(KERN_DEBUG)``. For ``print_hex_dump_debug()``/``print_hex_dump_bytes()``, format string is its ``prefix_str`` argument, if it is constant string; or ``hexdump`` 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. + + # 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 + +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. + +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. + +By doing so, modules tell dyndbg that they are have prdbgs with those +class_ids, and they authorize dyndbg to accept "class FOO" for the +module defining that classname. + +There are 2 types of classmaps: + + DD_CLASS_TYPE_DISJOINT_BITS: classes are independent, like DRM.debug + DD_CLASS_TYPE_LEVEL_NUM: classes are relative, ordered (V3 > V2) + +DYNDBG_CLASSMAP_PARAM - refers to a DEFINEd classmap, exposing the set +of defined classes to manipulation as a group. This interface +enforces the relatedness of classes of DD_CLASS_TYPE_LEVEL_NUM typed +classmaps; all classes are independent in the >control parser itself. + +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. + +Modules or module-groups (drm & drivers) can define multiple +classmaps, as long as they share the limited 0..62 per-module-group +_class_id range, without overlap. + +``#define DEBUG`` will enable all pr_debugs in scope, including any +class'd ones. This won't be reflected in the PARAM readback value, +but the pr_debug callsites can be toggled into agreement with the +param. -- 2.41.0
