On Fri, 03 Dec 2021, Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> wrote: > On Thu, Nov 25, 2021 at 04:27:18PM +0200, Jani Nikula wrote: >> On Thu, 25 Nov 2021, Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx> wrote: >> > On 25/11/2021 12:13, Ville Syrjälä wrote: >> >> On Thu, Nov 25, 2021 at 12:57:27PM +0200, Jani Nikula wrote: >> >>> On Thu, 25 Nov 2021, Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> wrote: >> >>>> On Wed, Nov 24, 2021 at 05:43:52PM +0200, Jani Nikula wrote: >> >>>>> On Wed, 24 Nov 2021, Ville Syrjala <ville.syrjala@xxxxxxxxxxxxxxx> wrote: >> >>>>>> From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> >> >>>>>> >> >>>>>> In order to encapsulate FBC harder let's just move the debugfs >> >>>>>> stuff into intel_fbc.c. >> >>>>> >> >>>>> Mmmh, I've kind of moved towards a split where i915_debugfs.c and >> >>>>> intel_display_debugfs.c have all the debugfs boilerplate, while the >> >>>>> implementation files have the guts with struct drm_i915_private *i915 >> >>>>> (or something more specific) and struct seq_file *m passed in. >> >>>>> >> >>>>> In some ways the split is arbitrary, but I kind of find the debugfs >> >>>>> boilerplate a distraction in the implementation files, and we also skip >> >>>>> building the debugfs files completely for CONFIG_DEBUG_FS=n. I don't >> >>>>> think I'd want to add #ifdefs on that spread around either. >> >>>> >> >>>> If we want to keep the debugfs in a separate file then we'll have to >> >>>> expose the guts of the FBC implementation in intel_fbc.h (or some other >> >>>> header) just for that, or we add a whole bunch of otherwise useless >> >>>> functions that pretend to provide some higher level of abstraction. >> >>>> >> >>>> Not really a fan of either of those options. >> >>> >> >>> Obviously I'm in favour of hiding the guts, no question about it. I'm >> >>> also very much in favour of moving the details out of our *debugfs.c >> >>> files. It's just a question of where to draw the line, and which side of >> >>> the line the debugfs boilerplate lands. >> >>> >> >>> Which leaves us either your approach in the patch at hand, or adding the >> >>> fbc helper functions for debugfs, which would be something like: >> >>> >> >>> intel_fbc_get_status >> >>> intel_fbc_get_false_color >> >>> intel_fbc_set_false_color >> >> >> >> So I guess you're suggesting that just the DEFINE_ATTRIBUTE >> >> and debugfs_create_file() stuff should remain in >> >> intel_display_debugfs.c? >> >> >> >> Not sure that approach has any benefits whatsoever. The get/set >> >> functions will need to be non-static and they'll get included in >> >> the binary whether or not debugfs is enabled or not (unless you >> >> lto it perhaps). If everything is in intel_fbc.c all that stuff >> >> just gets optimized out entirely when not needed. >> >> >> >> Also then I couldn't do this sort of stuff: >> >> if (fbc->funcs->set_false_color) >> >> debugfs_create_file(...) >> >> because that requires knowledge only available to intel_fbc.c. >> >> I'd need to add some kind of intel_fbc_has_false_color() thing >> >> just for that. >> > >> > Not guaranteeing I captured all the nuances here but how about an >> > approach similar to selftests? That is, have a separate file for debugfs >> > registration and bits (each "module" explicitly registers as in Ville's >> > patch), and have the owning "module" include the debugfs part at the end >> > of it. That way no exports, or defining too much API, would be needed. >> > And not needing common debugfs code to know the guts of any module. >> > Benefit of not compiling any of it when !CONFIG_DEBUG_FS is kept (or >> > gained, not even sure any more..). >> >> Frankly, I really dislike the "include code" part about selftests... > > We seem to have gone a bit off track in the discussion here. There > is no plan to do any kind of "include code" or anything here. All > I want to do is put the debugfs stuff into the same file as the > real implementation so that a) no implementation details need to > leak outside, b) the code gets optimized away when debufs is > disabled resulting in a smaller binary. Though I don't know if > anyone seriously compiles w/o debugfs anyway. > > I guess another benefit is that it's harder to forget to > update the debugfs code when making changes to the rest of the > implementation. I've lost count how many times I've forgeotten > to do that with the debugfs code living in a totally separate > file. Yeah, let's un-stall this. Acked-by: Jani Nikula <jani.nikula@xxxxxxxxx> on the change here, better abstractions and smaller interfaces being the main rationale for it. I think an insteresting question is, with all the debugfs stuff being static in intel_fbc.c, is the compiler actually smart enough to optimize the static code and data away when CONFIG_DEBUG_FS=n, even without #ifdefs? Or is that something you're already claiming above? If that's the case, my objection to adding #ifdefs just goes away. BR, Jani. -- Jani Nikula, Intel Open Source Graphics Center