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Wed, 18 Feb 2026 08:04:34 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id lNPvDJJylWmZCwAAD6G6ig (envelope-from ); Wed, 18 Feb 2026 08:04:34 +0000 Message-ID: <6440e721-daea-4d1d-a920-7eb786dec7f5@suse.de> Date: Wed, 18 Feb 2026 09:04:33 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] drm/gud: fix NULL crtc dereference on display disable To: Shenghao Yang , Ruben Wauters , Maarten Lankhorst , Maxime Ripard , David Airlie , Simona Vetter Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, kernel test robot , Dan Carpenter References: <20260203172630.10077-1-me@shenghaoyang.info> <0356024b-e951-4f87-98fc-2ecaf25f0ac4@suse.de> <8c5ff095-539e-4c63-b811-efb7de8002ce@shenghaoyang.info> Content-Language: en-US From: Thomas Zimmermann Autocrypt: addr=tzimmermann@suse.de; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Score: -4.30 X-Spam-Level: X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-0.982]; MIME_GOOD(-0.10)[text/plain]; RCVD_VIA_SMTP_AUTH(0.00)[]; FREEMAIL_TO(0.00)[shenghaoyang.info,aol.com,linux.intel.com,kernel.org,gmail.com,ffwll.ch]; ARC_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; RCPT_COUNT_SEVEN(0.00)[10]; FUZZY_RATELIMITED(0.00)[rspamd.com]; MID_RHS_MATCH_FROM(0.00)[]; FREEMAIL_ENVRCPT(0.00)[aol.com,gmail.com]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; RCVD_TLS_ALL(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:mid,imap1.dmz-prg2.suse.org:helo,suse.com:url] X-Spam-Flag: NO Hi Am 18.02.26 um 05:22 schrieb Shenghao Yang: > Hi, > > Thanks for taking a look! > > On 6/2/26 15:52, Thomas Zimmermann wrote: > >>>   +void gud_crtc_atomic_enable(struct drm_crtc *crtc, >>> +               struct drm_atomic_state *state) >>> +{ >>> +    struct drm_device *drm = crtc->dev; >>> +    struct gud_device *gdrm = to_gud_device(drm); >>> +    int idx; >>> + >>> +    if (!drm_dev_enter(drm, &idx)) >>> +        return; >>> + >>> +    if (crtc->state->mode_changed || crtc->state->connectors_changed) { >> I think you can do this unconditionally. Atomic_enable is supposed to be a full modeset and take some time.  For simple pageflips, this function doesn't run at all. >> > I was trying this with proptest and toggling DPMS - the atomic_disable() and > atomic_enable() functions get called in that path even if the mode doesn't > change. > > The driver in 6.12 LTS (before the atomic changes) didn't send > SET_CONTROLLER_ENABLE commands on DPMS changes either, so I thought it'd be > safer to do the same here. Leave it as it is if you like. But in DRM, we don't have real DPMS support for atomic modesetting. The DPMS on state is a full atomic_enable and the off and blanking states are atomic_disable IIRC. Doing that would be the correct handling. Best regards Thomas > >>> +        gud_usb_set_u8(gdrm, GUD_REQ_SET_CONTROLLER_ENABLE, 1); >>> +        gud_usb_set(gdrm, GUD_REQ_SET_STATE_COMMIT, 0, NULL, 0); >>> +    } >>> + >>> +    gud_usb_set_u8(gdrm, GUD_REQ_SET_DISPLAY_ENABLE, crtc->state->active); >> Why not write '1' unconditionally? IIRC the active bit is always true in atomic_enable. >> > Yup looking at drm_atomic_helper_commit_crtc_enable() the call to > atomic_enable() is skipped if !active - I'll sort this in v4! > > drm_atomic_helper_commit_crtc_enable(struct drm_device *dev, struct drm_atomic_state *state) > { > ... > for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state, new_crtc_state, i) { > ... > if (!new_crtc_state->active) > continue; > } > > Shenghao > > -- -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)