[AMD Official Use Only] +Harry
-----Original Message----- From: Daniel Vetter <dan...@ffwll.ch> Sent: Friday, July 23, 2021 11:23 AM To: Arnd Bergmann <a...@kernel.org> Cc: Daniel Vetter <dan...@ffwll.ch>; Ben Skeggs <bske...@redhat.com>; David Airlie <airl...@linux.ie>; Lyude Paul <ly...@redhat.com>; Arnd Bergmann <a...@arndb.de>; Ville Syrjälä <ville.syrj...@linux.intel.com>; Cornij, Nikola <nikola.cor...@amd.com>; dri-devel <dri-devel@lists.freedesktop.org>; Nouveau Dev <nouv...@lists.freedesktop.org>; Linux Kernel Mailing List <linux-ker...@vger.kernel.org> Subject: Re: [PATCH] drm/nouveau/kms/nv50-: fix build failure with CONFIG_BACKLIGHT=n On Fri, Jul 23, 2021 at 12:16:31PM +0200, Arnd Bergmann wrote: > On Fri, Jul 23, 2021 at 11:25 AM Daniel Vetter <dan...@ffwll.ch> wrote: > > > > On Fri, Jul 23, 2021 at 11:15 AM Arnd Bergmann <a...@kernel.org> wrote: > > > > > > From: Arnd Bergmann <a...@arndb.de> > > > > > > When the backlight support is disabled, the driver fails to build: > > > > > > drivers/gpu/drm/nouveau/dispnv50/disp.c: In function > > > 'nv50_sor_atomic_disable': > > > drivers/gpu/drm/nouveau/dispnv50/disp.c:1665:59: error: 'struct > > > nouveau_connector' has no member named 'backlight' > > > 1665 | struct nouveau_backlight *backlight = > > > nv_connector->backlight; > > > | ^~ > > > drivers/gpu/drm/nouveau/dispnv50/disp.c:1670:35: error: invalid use of > > > undefined type 'struct nouveau_backlight' > > > 1670 | if (backlight && backlight->uses_dpcd) { > > > | ^~ > > > drivers/gpu/drm/nouveau/dispnv50/disp.c:1671:64: error: invalid use of > > > undefined type 'struct nouveau_backlight' > > > 1671 | ret = drm_edp_backlight_disable(aux, > > > &backlight->edp_info); > > > | ^~ > > > > > > The patch that introduced the problem already contains some #ifdef > > > checks, so just add another one that makes it build again. > > > > > > Fixes: 6eca310e8924 ("drm/nouveau/kms/nv50-: Add basic DPCD > > > backlight support for nouveau") > > > Signed-off-by: Arnd Bergmann <a...@arndb.de> > > > > Can we just toss the idea that BACKTLIGHT=n is a reasonable config > > for drm drivers using backlights, and add depends BACKLIGHT to all > > of them? > > > > I mean this is a perfect source of continued patch streams to keep > > us all busy, but beyond that I really don't see the point ... I > > frankly have better things to do, and especially with the big > > drivers we have making backlight optional saves comparitively nothing. > > -Daniel > > Yes! I'd definitely be in favor of that, I've wasted way too much time > trying to sort through dependency loops and other problems with backlight > support. > > Maybe we should leave the drivers/video/fbdev/ drivers untouched in > this regard, at least for the moment, but for the drivers/gpu/drm > users of backlight that would be a nice simplification, and even the > smallest ones are unlikely to be used on systems that are too memory > constrained to deal with 4KB extra .text. Yeah I think we can do this entirely ad-hoc, i.e. any time the backlight wheel wobbles off again we nail it down for good for that driver with a depends on BACKGLIGHT and remove any lingering #ifdef all over. If you want maybe start out with the biggest drm drivers in a series, I think if nouveau/amdgpu/i915 folks ack this you're good to go to just convert as things get in the way. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation https://nam11.safelinks.protection.outlook.com/?url=http%3A%2F%2Fblog.ffwll.ch%2F&data=04%7C01%7Cnikola.cornij%40amd.com%7C48104ef3c5724531e8f708d94dedcf83%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637626506075627495%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=KWVzpQyZsBh4jo522b36pru1zPBxxW2wvXUAjJ6u3G8%3D&reserved=0