On Fri, Mar 17, 2017 at 06:01:41PM +0900, Michel Dänzer wrote:
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 michel.daenzer@amd.com
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.
So one semi-crazy idea I had was: 12:18 < vsyrjala> daniels: hmm. given that the fb_helper doesn't implement a modeset in set_par, i guess what we really should do is look at the currently active crtcs and see if the mode on one of them more or less matches what the user is asking for
I tried to trip this current check by booting with a big screen and later switching to a small screen. For some reason that worked out just fine, so I'm not even sure what kind of values we stuff into xres & co.
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 michel.daenzer@amd.com
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)) {-- 2.11.0
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-- Earthling Michel Dänzer | http://www.amd.com Libre software enthusiast | Mesa and X developer