Re: [PATCH v3] drm/gud: fix NULL crtc dereference on display disable

[Thomas Zimmermann <tzimmermann@suse.de>]

Hi

Am 18.02.26 um 15:29 schrieb Shenghao Yang:
> Hi,
>
> On 18/2/26 16:04, Thomas Zimmermann wrote:
>
>> 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.
> Ah - gotcha. I'll do some testing with the conditional removed.
> The worry about changing command sequences was a bit pedantic anyway -
> DPMS would have caused an instant oops in the current tree and nobody else
> has reported anything yet.
>
> Would y'all be happy to take a v5 afterwards? Apologies for all the
> iterations here :/

I'm OK with that. No worries.

Best regards
Thomas

>
> Thanks,
>
> 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)