Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751074AbdCQJBs (ORCPT ); Fri, 17 Mar 2017 05:01:48 -0400 Received: from [148.251.143.178] ([148.251.143.178]:33705 "EHLO netline-mail3.netline.ch" rhost-flags-FAIL-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1750885AbdCQJBr (ORCPT ); Fri, 17 Mar 2017 05:01:47 -0400 From: =?UTF-8?Q?Michel_D=c3=a4nzer?= Subject: Re: [PATCH] drm/fb-helper: Only reject FB changes if FB_MISC_USER_EVENT is set To: =?UTF-8?B?VmlsbGUgU3lyasOkbMOk?= Cc: linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, Stefan Agner References: <20170316095553.1586-1-michel@daenzer.net> <20170316100900.GC31595@intel.com> Message-ID: <87d59360-8419-b547-7b6b-32afedcf1330@daenzer.net> Date: Fri, 17 Mar 2017 18:01:41 +0900 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: <20170316100900.GC31595@intel.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3823 Lines: 85 On 16/03/17 07:09 PM, Ville Syrjälä wrote: > On Thu, Mar 16, 2017 at 06:55:53PM +0900, Michel Dänzer wrote: >> From: Michel Dänzer >> >> Otherwise this can also prevent modesets e.g. for switching VTs. >> >> FB_MISC_USER_EVENT is set when the request originates from userspace, >> which is what we're interested in here according to the DRM_DEBUG >> output. > > So why is the kernel allowed to violate this? > > The checks look somewhat bogus to me anyway. The 'virtual size == fb size' > check makes some kind of sense. Although I don't see why the virtual > resolution couldn't be smaller than the fb size. But requiring that the > visible resolutionn matches the fb size as well definitely seems wrong. Agreed on all counts. So, I think what's needed is almost a revert of 865afb11949e, except for the bits_per_pixel comparison, since we really can't change that. See diff below. Does that make sense? Stefan, would this break any test case you wrote your patch for? diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c index f6d4d9700734..f4f70ce24fcc 100644 --- a/drivers/gpu/drm/drm_fb_helper.c +++ b/drivers/gpu/drm/drm_fb_helper.c @@ -1260,8 +1260,8 @@ int drm_fb_helper_check_var(struct fb_var_screeninfo *var, * to KMS, hence fail if different settings are requested. */ if (var->bits_per_pixel != fb->format->cpp[0] * 8 || - var->xres != fb->width || var->yres != fb->height || - var->xres_virtual != fb->width || var->yres_virtual != fb->height) { + var->xres > fb->width || var->yres > fb->height || + var->xres_virtual > fb->width || var->yres_virtual > fb->height) { DRM_DEBUG("fb userspace requested width/height/bpp different than current fb " "request %dx%d-%d (virtual %dx%d) > %dx%d-%d\n", var->xres, var->yres, var->bits_per_pixel, >> Bugzilla: https://bugs.freedesktop.org/99841 >> Fixes: 865afb11949e ("drm/fb-helper: reject any changes to the fbdev") >> Signed-off-by: Michel Dänzer >> --- >> >> I'm not entirely sure why the values can not match for a VT switch. If >> anybody thinks this just papers over the real issue, please speak up. >> >> drivers/gpu/drm/drm_fb_helper.c | 7 ++++--- >> 1 file changed, 4 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c >> index f6d4d9700734..9663f3b8f287 100644 >> --- a/drivers/gpu/drm/drm_fb_helper.c >> +++ b/drivers/gpu/drm/drm_fb_helper.c >> @@ -1259,9 +1259,10 @@ int drm_fb_helper_check_var(struct fb_var_screeninfo *var, >> * Changes struct fb_var_screeninfo are currently not pushed back >> * to KMS, hence fail if different settings are requested. >> */ >> - if (var->bits_per_pixel != fb->format->cpp[0] * 8 || >> - var->xres != fb->width || var->yres != fb->height || >> - var->xres_virtual != fb->width || var->yres_virtual != fb->height) { >> + if ((info->flags & FBINFO_MISC_USEREVENT) && >> + (var->bits_per_pixel != fb->format->cpp[0] * 8 || >> + var->xres != fb->width || var->yres != fb->height || >> + var->xres_virtual != fb->width || var->yres_virtual != fb->height)) { >> DRM_DEBUG("fb userspace requested width/height/bpp different than current fb " >> "request %dx%d-%d (virtual %dx%d) > %dx%d-%d\n", >> var->xres, var->yres, var->bits_per_pixel, >> -- >> 2.11.0 >> >> _______________________________________________ >> dri-devel mailing list >> dri-devel@lists.freedesktop.org >> https://lists.freedesktop.org/mailman/listinfo/dri-devel > -- Earthling Michel Dänzer | http://www.amd.com Libre software enthusiast | Mesa and X developer