Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753340AbcKPOIe (ORCPT ); Wed, 16 Nov 2016 09:08:34 -0500 Received: from mga14.intel.com ([192.55.52.115]:59776 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751589AbcKPOId (ORCPT ); Wed, 16 Nov 2016 09:08:33 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.31,500,1473145200"; d="scan'208";a="787150571" From: Jani Nikula To: Tomeu Vizoso Cc: David Airlie , Intel Graphics Development , "linux-kernel\@vger.kernel.org" , "dri-devel\@lists.freedesktop.org" , Thierry Reding , Daniel Vetter Subject: Re: [Intel-gfx] [PATCH v11 3/4] drm/i915: Use new CRC debugfs API In-Reply-To: Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo 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> Date: Wed, 16 Nov 2016 16:08:30 +0200 Message-ID: <87eg2b1pr5.fsf@intel.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3397 Lines: 76 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. ;) BR, Jani. > > Regards, > > Tomeu -- Jani Nikula, Intel Open Source Technology Center