Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932671AbcKPON4 (ORCPT ); Wed, 16 Nov 2016 09:13:56 -0500 Received: from mail-wm0-f65.google.com ([74.125.82.65]:33286 "EHLO mail-wm0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932263AbcKPONz (ORCPT ); Wed, 16 Nov 2016 09:13:55 -0500 Date: Wed, 16 Nov 2016 15:13:50 +0100 From: Daniel Vetter To: Jani Nikula Cc: Tomeu Vizoso , Intel Graphics Development , "linux-kernel@vger.kernel.org" , "dri-devel@lists.freedesktop.org" , Daniel Vetter Subject: Re: [Intel-gfx] [PATCH v11 3/4] drm/i915: Use new CRC debugfs API Message-ID: <20161116141350.cxec4jwklwoluq6r@phenom.ffwll.local> Mail-Followup-To: Jani Nikula , Tomeu Vizoso , Intel Graphics Development , "linux-kernel@vger.kernel.org" , "dri-devel@lists.freedesktop.org" , Daniel Vetter References: <1475767268-14379-1-git-send-email-tomeu.vizoso@collabora.com> <1475767268-14379-4-git-send-email-tomeu.vizoso@collabora.com> <87inrq2vee.fsf@intel.com> <20161115071609.GI8202@suiko.acc.umu.se> <87a8d12lmy.fsf@intel.com> <87h9771t0k.fsf@intel.com> <87eg2b1pr5.fsf@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87eg2b1pr5.fsf@intel.com> X-Operating-System: Linux phenom 4.6.0-1-amd64 User-Agent: NeoMutt/20161104 (1.7.1) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3650 Lines: 73 On Wed, Nov 16, 2016 at 04:08:30PM +0200, Jani Nikula wrote: > On Wed, 16 Nov 2016, Tomeu Vizoso wrote: > > On 16 November 2016 at 13:58, Jani Nikula wrote: > >> On Wed, 16 Nov 2016, Tomeu Vizoso wrote: > >>> On 15 November 2016 at 09:27, Jani Nikula wrote: > >>>> On Tue, 15 Nov 2016, David Weinehall wrote: > >>>>> On Mon, Nov 14, 2016 at 12:44:25PM +0200, Jani Nikula wrote: > >>>>>> On Thu, 06 Oct 2016, Tomeu Vizoso wrote: > >>>>>> > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c > >>>>>> > index 23a6c7213eca..7412a05fa5d9 100644 > >>>>>> > --- a/drivers/gpu/drm/i915/intel_display.c > >>>>>> > +++ b/drivers/gpu/drm/i915/intel_display.c > >>>>>> > @@ -14636,6 +14636,7 @@ static const struct drm_crtc_funcs intel_crtc_funcs = { > >>>>>> > .page_flip = intel_crtc_page_flip, > >>>>>> > .atomic_duplicate_state = intel_crtc_duplicate_state, > >>>>>> > .atomic_destroy_state = intel_crtc_destroy_state, > >>>>>> > + .set_crc_source = intel_crtc_set_crc_source, > >>>>>> > }; > >>>>>> > > >>>>>> > /** > >>>>>> > diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h > >>>>>> > index 737261b09110..31894b7c6517 100644 > >>>>>> > --- a/drivers/gpu/drm/i915/intel_drv.h > >>>>>> > +++ b/drivers/gpu/drm/i915/intel_drv.h > >>>>>> > @@ -1844,6 +1844,14 @@ void intel_color_load_luts(struct drm_crtc_state *crtc_state); > >>>>>> > /* intel_pipe_crc.c */ > >>>>>> > int intel_pipe_crc_create(struct drm_minor *minor); > >>>>>> > void intel_pipe_crc_cleanup(struct drm_minor *minor); > >>>>>> > +#ifdef CONFIG_DEBUG_FS > >>>>>> > +int intel_crtc_set_crc_source(struct drm_crtc *crtc, const char *source_name, > >>>>>> > + size_t *values_cnt); > >>>>>> > +#else > >>>>>> > +static inline int intel_crtc_set_crc_source(struct drm_crtc *crtc, > >>>>>> > + const char *source_name, > >>>>>> > + size_t *values_cnt) { return 0; } > >>>>>> > +#endif > >>>>>> > >>>>>> "inline" here doesn't work because it's used as a function pointer. > >>>>>> > >>>>>> Is it better to have a function that returns 0 for .set_crc_source, or > >>>>>> to set .set_crc_source to NULL when CONFIG_DEBUG_FS=n? > >>>>> > >>>>> I'd say that whenever we have a function pointer we should have a dummy > >>>>> function without side-effects for this kind of things. > >>>> > >>>> Whoever calls .set_crc_source could do smarter things depending on the > >>>> hook not being there vs. just silently plunging on. > >>> > >>> In this specific case, when CONFIG_DEBUG_FS=n it doesn't make any > >>> sense to call that callback, so I think we should have a dummy > >>> implementation to avoid adding an ifdef to the .c. > >> > >> We don't want the ifdef to the .c file, but we could do > >> > >> #ifdef CONFIG_DEBUG_FS > >> int intel_crtc_set_crc_source(struct drm_crtc *crtc, const char *source_name, > >> size_t *values_cnt); > >> #else > >> #define intel_crtc_set_crc_source NULL > >> #endif > > > > Sounds good to me, and though I don't have any objections, wonder why > > this isn't a common idiom in the DRM subsystem. I was able to find > > only one instance: drm_compat_ioctl. > > Heh, and it was I who suggested that too. Maybe get a second opinion. ;) Personally I like drm_compat_ioctl, we should spread it far&wide. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch