On Fri, Dec 03, 2021 at 11:55:43AM +0200, Jani Nikula wrote: > 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? Yes it all disappeared from the binary when I tried it. Only thing left was an empty intel_fbc_debugfs_register(). -- Ville Syrjälä Intel
