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[92.176.231.205]) by smtp.gmail.com with ESMTPSA id m8-20020a05600c4f4800b003942a244f51sm28267502wmq.42.2022.06.07.11.23.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 07 Jun 2022 11:23:48 -0700 (PDT) From: Javier Martinez Canillas To: linux-kernel@vger.kernel.org Cc: dri-devel@lists.freedesktop.org, Thomas Zimmermann , Laszlo Ersek , Alex Williamson , Gerd Hoffmann , kvm@vger.kernel.org, Greg Kroah-Hartman , Daniel Vetter , Javier Martinez Canillas , Daniel Vetter , Helge Deller , linux-fbdev@vger.kernel.org Subject: [PATCH v6 3/5] fbdev: Disable sysfb device registration when removing conflicting FBs Date: Tue, 7 Jun 2022 20:23:36 +0200 Message-Id: <20220607182338.344270-4-javierm@redhat.com> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220607182338.344270-1-javierm@redhat.com> References: <20220607182338.344270-1-javierm@redhat.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org The platform devices registered by sysfb match with firmware-based DRM or fbdev drivers, that are used to have early graphics using a framebuffer provided by the system firmware. DRM or fbdev drivers later are probed and remove all conflicting framebuffers, leading to these platform devices for generic drivers to be unregistered. But the current solution has a race, since the sysfb_init() function could be called after a DRM or fbdev driver is probed and request to unregister the devices for drivers with conflicting framebuffes. To prevent this, disable any future sysfb platform device registration by calling sysfb_disable(), if a driver requests to remove the conflicting framebuffers. Suggested-by: Daniel Vetter Signed-off-by: Javier Martinez Canillas Reviewed-by: Daniel Vetter --- Changes in v6: - Move the sysfb_disable() before the remove conflicting framebuffers loop (Daniel Vetter). Changes in v5: - Move the sysfb_disable() call at conflicting framebuffers again to avoid the need of a DRIVER_FIRMWARE capability flag. - Add Daniel Vetter's Reviewed-by tag again since reverted to the old patch that he already reviewed in v2. Changes in v3: - Call sysfb_disable() when a DRM dev and a fbdev are registered rather than when conflicting framebuffers are removed (Thomas Zimmermann). - Call sysfb_disable() when a fbdev framebuffer is registered rather than when conflicting framebuffers are removed (Thomas Zimmermann). - Drop Daniel Vetter's Reviewed-by tag since patch changed a lot. Changes in v2: - Explain in the commit message that fbmem has to unregister the device as fallback if a driver registered the device itself (Daniel Vetter). - Also explain that fallback in a comment in the code (Daniel Vetter). - Don't encode in fbmem the assumption that sysfb will always register platform devices (Daniel Vetter). - Add a FIXME comment about drivers registering devices (Daniel Vetter). drivers/video/fbdev/core/fbmem.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c index 2fda5917c212..e0720fef0ee6 100644 --- a/drivers/video/fbdev/core/fbmem.c +++ b/drivers/video/fbdev/core/fbmem.c @@ -19,6 +19,7 @@ #include #include #include +#include #include #include #include @@ -1764,6 +1765,17 @@ int remove_conflicting_framebuffers(struct apertures_struct *a, do_free = true; } + /* + * If a driver asked to unregister a platform device registered by + * sysfb, then can be assumed that this is a driver for a display + * that is set up by the system firmware and has a generic driver. + * + * Drivers for devices that don't have a generic driver will never + * ask for this, so let's assume that a real driver for the display + * was already probed and prevent sysfb to register devices later. + */ + sysfb_disable(); + mutex_lock(®istration_lock); do_remove_conflicting_framebuffers(a, name, primary); mutex_unlock(®istration_lock);