On Mon, 2010-04-19 at 19:22 +0200, Jan Kiszka wrote: > Philippe Gerum wrote: > > On Mon, 2010-04-19 at 18:25 +0200, Philippe Gerum wrote: > >> On Mon, 2010-04-19 at 18:14 +0200, Jan Kiszka wrote: > >>> Philippe Gerum wrote: > >>>> On Mon, 2010-04-19 at 17:58 +0200, Jan Kiszka wrote: > >>>>> Gilles Chanteperdrix wrote: > >>>>>> Jan Kiszka wrote: > >>>>>>> Gilles Chanteperdrix wrote: > >>>>>>>> Jan Kiszka wrote: > >>>>>>>>> Gilles Chanteperdrix wrote: > >>>>>>>>>> Jan Kiszka wrote: > >>>>>>>>>>> Gilles Chanteperdrix wrote: > >>>>>>>>>>>> Hi, > >>>>>>>>>>>> > >>>>>>>>>>>> I found some code which was referencing directly some > >>>>>>>>>>>> CONFIG_XENO_OPT_DEBUG_ variables with things like: > >>>>>>>>>>>> > >>>>>>>>>>>> #ifdef CONFIG_XENO_OPT_DEBUG_FOO > >>>>>>>>>>>> > >>>>>>>>>>>> This usage is incompatible with the pre-requisites of the > >>>>>>>>>>>> assert.h > >>>>>>>>>>>> header that CONFIG_XENO_OPT_DEBUG_FOO should be defined at all > >>>>>>>>>>>> times. > >>>>>>>>>>>> While grepping for CONFIG_XENO_OPT_DEBUG_, I found that we also > >>>>>>>>>>>> have > >>>>>>>>>>>> many duplicates of construction like: > >>>>>>>>>>>> #ifndef CONFIG_XENO_OPT_DEBUG_FOO > >>>>>>>>>>>> #define CONFIG_XENO_OPT_DEBUG_FOO 0 > >>>>>>>>>>>> #endif /* CONFIG_XENO_OPT_DEBUG_FOO */ > >>>>>>>>>>>> > >>>>>>>>>>>> So, a patch follows which: > >>>>>>>>>>>> - replace the #ifdef with some #if XENO_DEBUG(FOO) > >>>>>>>>>>> Should probably come as a separate patch. > >>>>>>>>>> Come on, the patch is simple, one patch for this is enough. > >>>>>>>>> One part is an obvious fix, the other a refactoring under > >>>>>>>>> discussion. > >>>>>>>>> > >>>>>>>>>>>> - move all the initializations to assert.h > >>>>>>>>>>>> > >>>>>>>>>>>> This will make any reference to CONFIG_XENO_OPT_DEBUG_FOO > >>>>>>>>>>>> outside of > >>>>>>>>>>>> assert.h suspicious, and easy to detect. > >>>>>>>>>>> How many duplicates did you find? > >>>>>>>>>> A lot, especially for CONFIG_XENO_OPT_DEBUG_NUCLEUS > >>>>>>>>> That's because the CONFIG_XENO_OPT_DEBUG_NUCLEUS defines were > >>>>>>>>> misplaced. > >>>>>>>>> Besides that we had one CONFIG_XENO_OPT_DEBUG_QUEUE duplicate, but > >>>>>>>>> tons > >>>>>>>>> of proper users. I don't see such an immediate need. > >>>>>>>>> > >>>>>>>>> When adding this kind of switching, it's till more handy to have > >>>>>>>>> things > >>>>>>>>> locally in your subsystem. That also makes reviewing easier when you > >>>>>>>>> only find changes in files that belong to a subsystem. > >>>>>>>> That is not the main point, the main point is that putting all these > >>>>>>>> defines in one files allow to detect easily direct references to the > >>>>>>>> symbols. > >>>>>>>> > >>>>>>>>>>> Generally, I'm more a fan of decentralized management here (e.g. > >>>>>>>>>>> this > >>>>>>>>>>> avoids needless patch conflicts in central files). > >>>>>>>>>> If we maintain the list in alphabetical order (which I have done), > >>>>>>>>>> we > >>>>>>>>>> reduce the likeliness for conflicts. The aim of doing this is also > >>>>>>>>>> that > >>>>>>>>>> I can check that the sources are clean with: > >>>>>>>>>> > >>>>>>>>>> find xenomai-2.5 ! -name 'assert.h' -name '*.[ch]' | xargs grep > >>>>>>>>>> CONFIG_XENO_OPT_DEBUG_ > >>>>>>>>>> > >>>>>>>>>> And that I can add this test to the automated build test. > >>>>>>>>>> > >>>>>>>>>> Note that forgetting to add a #define to the list yields an > >>>>>>>>>> immediate > >>>>>>>>>> compilation error. So, the patch makes things completely safe. > >>>>>>>>> What did you change to make this happen (for new users of > >>>>>>>>> XENO_DEBUG)? > >>>>>>>> Nothing. If you forget to add the define, and do not enable the debug > >>>>>>>> option (which everybody does most of the time), you get a compilation > >>>>>>>> error. > >>>>>>> The alternative (and decentralized) approach for fixing this consists > >>>>>>> of > >>>>>>> Kconfig magic for generating the value: > >>>>>>> > >>>>>>> config XENO_OPT_DEBUG_FOO > >>>>>>> bool "..." > >>>>>>> > >>>>>>> config XENO_OPT_DEBUG_FOO_P > >>>>>>> int > >>>>>>> default "1" if XENO_OPT_DEBUG_FOO > >>>>>>> default "0" > >>>>>>> > >>>>>>> and XENO_DEBUG() could be extended to test for > >>>>>>> CONFIG_XENO_OPT_DEBUG_FOO_P when given "FOO". I'm just not sure if > >>>>>>> this > >>>>>>> can be expressed for legacy 2.4 kernels, so it might have to wait for > >>>>>>> Xenomai 3. > >>>> Well, actually, I would not merge this in Xenomai 3. I find this rather > >>>> overkill; mainline first I mean, and mainline, i.e. the Xenomai code > >>>> base only requires a simple and straightforward way to get debug > >>>> switches right. Having to make Kconfig a kitchen sink for some unknown > >>>> out of tree modules to be happy is not really my preferred approach in > >>>> this particular case. > >>>> > >>>> Don't get me wrong, I'm not opposed to a more decentralized approach on > >>>> the paper, it's just that I only care about the mainline tree here. > >>> The point is not out-of-tree but robustness. Neither the current > >>> decentralized #ifdef-#define nor its centralized brother meet this > >>> criteria. An approach like the above which forces you to provide all > >>> required bits before any of the cases (disabled/enabled) starts to work > >>> does so. > >> Flexibility and robustness have to be combined. Explicit declaration in > >> Kconfig is against flexibility, because this is one external thing more > >> to take care of, for adding something as simple as a debug switch. So if > > You already have to take care of Kconfig if you want a debug switch. >
The point you have to keep in mind to understand why I would not merge anything like this is that adding a config knob to enable a particular debug subsystem, is fine, smart and makes a lot of sense. But having to tweak the config system to deal with obscure internal issues we may have for using those knobs is wrong. > Jan > -- Philippe. _______________________________________________ Xenomai-core mailing list Xenomai-core@gna.org https://mail.gna.org/listinfo/xenomai-core
