On Tue, Jun 09, 2020 at 01:45:58PM +0300, Stanimir Varbanov wrote:

+level
+    The given level will be a bitmask ANDed with the level of the each ``pr_debug()``
+    callsite. This will allow to group debug messages and show only those of the
+    same level.  The -p flag takes precedence over the given level. Note that we can
+    have up to five groups of debug messages.

That doesn't sound like a "level".  printk has levels.  If you ask for
"level 3" messages, you get messages from levels 0, 1, 2, and 3.  These
seem like "types" or "groups" or something.

+  // enable all messages in file with 0x01 level bitmask
+  nullarbor:~ # echo -n 'file foo.c level 0x01 +p' >
+                                <debugfs>/dynamic_debug/control