linux-kernel - Re: [PATCH 2/3] drm: Reorganize drm_pending

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Date:   Thu, 06 Jul 2017 08:36:00 -0700
From:   Keith Packard <keithp@...thp.com>
To:     Daniel Vetter <daniel@...ll.ch>
Cc:     linux-kernel@...r.kernel.org, Dave Airlie <airlied@...hat.com>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH 2/3] drm: Reorganize drm_pending_event to support future event types

Daniel Vetter <daniel@...ll.ch> writes:

> A few nits below, but looks good otherwise.

Thanks.

>>  static struct drm_pending_vblank_event *create_vblank_event(
>> -		struct drm_device *dev, uint64_t user_data)
>> +		struct drm_device *dev, struct drm_crtc *crtc, uint64_t user_data)
>
> Nit: Please also drop the dev argument, we have crtc->dev easily
> available. That fits better into my long-term goal of getting rid of the
> (dev, pipe) pairs everywhere in the vblank code and fully switching over
> to drm_crtc *.

As 'dev' isn't used anyways, this seems like a fine plan.

>> +	switch (e->event.base.type) {
>> +	case DRM_EVENT_VBLANK:
>> +	case DRM_EVENT_FLIP_COMPLETE:
>> +		if (seq)
>> +			e->event.vbl.sequence = (u32) seq;
>> +		if (now) {
>> +			e->event.vbl.tv_sec = now->tv_sec;
>> +			e->event.vbl.tv_usec = now->tv_nsec / 1000;
>> +		}
>> +		break;
>> +	}
>
> Not sure why this change? Also prep for the new, presumably extended
> events? Seems at least slightly inconsistent with other paths, where we
> still unconditionally fill it in.

Yes, this prepares for the new events to make that patch smaller. The
places where the data are still unconditionally assigned should know
that the event in the struct is either a VBLANK or FLIP_COMPLETE.

>> +	struct drm_crtc *crtc = drm_crtc_from_index(dev, pipe);
>
> This'll oops on ums drivers since kms isn't set up.

How about this fix?

diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
index 857b7cf011e1..e39b2bd074e4 100644
--- a/drivers/gpu/drm/drm_vblank.c
+++ b/drivers/gpu/drm/drm_vblank.c
@@ -1355,7 +1355,6 @@ static int drm_queue_vblank_event(struct drm_device *dev, unsigned int pipe,
 				  union drm_wait_vblank *vblwait,
 				  struct drm_file *file_priv)
 {
-	struct drm_crtc *crtc = drm_crtc_from_index(dev, pipe);
 	struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
 	struct drm_pending_vblank_event *e;
 	struct timespec now;
@@ -1373,7 +1372,12 @@ static int drm_queue_vblank_event(struct drm_device *dev, unsigned int pipe,
 	e->event.base.type = DRM_EVENT_VBLANK;
 	e->event.base.length = sizeof(e->event.vbl);
 	e->event.vbl.user_data = vblwait->request.signal;
-	e->event.vbl.crtc_id = crtc ? crtc->base.id : 0;
+	e->event.vbl.crtc_id = 0;
+	if (drm_core_check_feature(dev, DRIVER_MODESET)) {
+		struct drm_crtc *crtc = drm_crtc_from_index(dev, pipe);
+		if (crtc)
+			e->event.vbl.crtc_id = crtc->base.id;
+	}
 
 	spin_lock_irqsave(&dev->event_lock, flags);

> Or maybe I shouldn't have told you this and seized this opportunity to
> break all the old drivers :-)

You now know my evil plan :-)

-- 
-keith

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