linux-kernel - Re: [PATCH 3/3] drm: Add CRTC_GET_SEQUENCE and CRTC_QUEUE

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Message-ID: <55be11c9-d1e0-d6f9-e497-512e9926eff4@daenzer.net>
Date:   Wed, 2 Aug 2017 18:45:33 +0900
From:   Michel Dänzer <michel@...nzer.net>
To:     Keith Packard <keithp@...thp.com>,
        Dave Airlie <airlied@...hat.com>,
        Daniel Vetter <daniel@...ll.ch>
Cc:     linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH 3/3] drm: Add CRTC_GET_SEQUENCE and CRTC_QUEUE_SEQUENCE
 ioctls [v2]

On 01/08/17 02:03 PM, Keith Packard wrote:
> These provide crtc-id based functions instead of pipe-number, while
> also offering higher resolution time (ns) and wider frame count (64)
> as required by the Vulkan API.
> 
> v2:
> 
>  * Check for DRIVER_MODESET in new crtc-based vblank ioctls
> 
> 	Failing to check this will oops the driver.
> 
>  * Ensure vblank interupt is running in crtc_get_sequence ioctl
> 
> 	The sequence and timing values are not correct while the
> 	interrupt is off, so make sure it's running before asking for
> 	them.
> 
>  * Short-circuit get_sequence if the counter is enabled and accurate
> 
> 	Steal the idea from the code in wait_vblank to avoid the
> 	expense of drm_vblank_get/put
> 
>  * Return active state of crtc in crtc_get_sequence ioctl
> 
> 	Might be useful for applications that aren't in charge of
> 	modesetting?
> 
>  * Use drm_crtc_vblank_get/put in new crtc-based vblank sequence ioctls
> 
> 	Daniel Vetter prefers these over the old drm_vblank_put/get
> 	APIs.
> 
>  * Return s64 ns instead of u64 in new sequence event
> 
> Suggested-by:  Daniel Vetter <daniel@...ll.ch>
> Suggested-by: Ville Syrjälä <ville.syrjala@...ux.intel.com>
> Signed-off-by: Keith Packard <keithp@...thp.com>

[...]

> +#define DRM_CRTC_SEQUENCE_NEXT_ON_MISS		0x00000002	/* Use next sequence if we've missed */

Do you have userspace making use of DRM_CRTC_SEQUENCE_NEXT_ON_MISS? If
not, drop it.

> +#define DRM_CRTC_SEQUENCE_FIRST_PIXEL_OUT	0x00000004	/* Signal when first pixel is displayed */

I thought there was consensus that this flag is pointless.


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer