On Wed, Jun 10, 2020 at 01:29:20PM +0300, Stanimir Varbanov wrote: > Hi Greg, > > On 6/9/20 2:16 PM, Greg Kroah-Hartman wrote: > > On Tue, Jun 09, 2020 at 01:45:58PM +0300, Stanimir Varbanov wrote: > >> This adds description of the level bitmask feature. > >> > >> Cc: Jonathan Corbet <corbet@xxxxxxx> (maintainer:DOCUMENTATION) > >> > >> Signed-off-by: Stanimir Varbanov <stanimir.varbanov@xxxxxxxxxx> > >> --- > >> Documentation/admin-guide/dynamic-debug-howto.rst | 10 ++++++++++ > >> 1 file changed, 10 insertions(+) > >> > >> diff --git a/Documentation/admin-guide/dynamic-debug-howto.rst b/Documentation/admin-guide/dynamic-debug-howto.rst > >> index 0dc2eb8e44e5..c2b751fc8a17 100644 > >> --- a/Documentation/admin-guide/dynamic-debug-howto.rst > >> +++ b/Documentation/admin-guide/dynamic-debug-howto.rst > >> @@ -208,6 +208,12 @@ line > >> line -1605 // the 1605 lines from line 1 to line 1605 > >> line 1600- // all lines from line 1600 to the end of the file > >> > >> +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. > > > > As was pointed out, this isn't a "level", it's some arbitrary type of > > "grouping". > > Yes, it is grouping of KERN_DEBUG level messages by importance (my > fault, I put incorrect name). What is important is driver author > decision. Usually when the driver is huge and has a lot of debug > messages it is not practical to enable all of them to chasing a > particular bug or issue. You know that debugging (printk) add delays > which could hide or rise additional issue(s) which would complicate > debug and waste time. That is why it is possible to turn on and off debugging messages on a function/line basis already. Why not just use that instead? > For the Venus driver I have defined three groups of KERN_DEBUG - low, > medium and high (again the driver author(s) will decide what the > importance is depending on his past experience). > > There is another point where the debugging is made by person who is not > familiar with the driver code. In that case he/she cannot enable lines > or range of lines because he don't know the details. Here the grouping > by importance could help. And they will really know what "low/medium/high" are? Anyway, that makes a bit more sense, but the documentation could use a lot more in order to describe this type of behavior, and what is expected by both driver authors, and users of the interface. thanks, greg k-h
