From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 5A626C43217 for ; Fri, 3 Dec 2021 10:06:19 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id E965F73CBE; Fri, 3 Dec 2021 10:06:18 +0000 (UTC) Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) by gabe.freedesktop.org (Postfix) with ESMTPS id EC92C73CBD for ; Fri, 3 Dec 2021 10:06:17 +0000 (UTC) X-IronPort-AV: E=McAfee;i="6200,9189,10186"; a="237176453" X-IronPort-AV: E=Sophos;i="5.87,284,1631602800"; d="scan'208";a="237176453" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Dec 2021 02:06:17 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.87,284,1631602800"; d="scan'208";a="513651021" Received: from stinkbox.fi.intel.com (HELO stinkbox) ([10.237.72.171]) by orsmga008.jf.intel.com with SMTP; 03 Dec 2021 02:06:13 -0800 Received: by stinkbox (sSMTP sendmail emulation); Fri, 03 Dec 2021 12:06:13 +0200 Date: Fri, 3 Dec 2021 12:06:13 +0200 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: Jani Nikula Message-ID: References: <20211124113652.22090-1-ville.syrjala@linux.intel.com> <20211124113652.22090-12-ville.syrjala@linux.intel.com> <87pmqplft3.fsf@intel.com> <87bl28lcyw.fsf@intel.com> <91e37161-7148-5d71-2efa-0176fbe2f468@linux.intel.com> <871r34l395.fsf@intel.com> <87lf12gggw.fsf@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <87lf12gggw.fsf@intel.com> X-Patchwork-Hint: comment Subject: Re: [Intel-gfx] [PATCH 11/20] drm/i915/fbc: Move FBC debugfs stuff into intel_fbc.c X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Daniel Vetter , intel-gfx@lists.freedesktop.org Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On Fri, Dec 03, 2021 at 11:55:43AM +0200, Jani Nikula wrote: > On Fri, 03 Dec 2021, Ville Syrjälä wrote: > > On Thu, Nov 25, 2021 at 04:27:18PM +0200, Jani Nikula wrote: > >> On Thu, 25 Nov 2021, Tvrtko Ursulin 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 wrote: > >> >>>> On Wed, Nov 24, 2021 at 05:43:52PM +0200, Jani Nikula wrote: > >> >>>>> On Wed, 24 Nov 2021, Ville Syrjala wrote: > >> >>>>>> From: Ville Syrjälä > >> >>>>>> > >> >>>>>> 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 > > 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