Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753200AbcKPOEo (ORCPT ); Wed, 16 Nov 2016 09:04:44 -0500 Received: from mail-wm0-f66.google.com ([74.125.82.66]:35183 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751589AbcKPOEn (ORCPT ); Wed, 16 Nov 2016 09:04:43 -0500 MIME-Version: 1.0 In-Reply-To: <87h9771t0k.fsf@intel.com> 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> From: Tomeu Vizoso Date: Wed, 16 Nov 2016 15:04:20 +0100 X-Google-Sender-Auth: q4XTGBUDuxrg1d2UfmimDL23UWY Message-ID: Subject: Re: [Intel-gfx] [PATCH v11 3/4] drm/i915: Use new CRC debugfs API To: Jani Nikula Cc: David Airlie , Intel Graphics Development , "linux-kernel@vger.kernel.org" , "dri-devel@lists.freedesktop.org" , Thierry Reding , Daniel Vetter Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3115 Lines: 66 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. Regards, Tomeu