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From: "Michel Dänzer" <michel@daenzer.net>
To: Stefan Lengfeld <contact@stefanchrist.eu>,
	Maxime Ripard <maxime.ripard@free-electrons.com>
Cc: linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
	Daniel Vetter <daniel.vetter@intel.com>
Subject: Re: [PATCH v3 2/2] drm/fb-helper: implement ioctl FBIO_WAITFORVSYNC
Date: Wed, 22 Feb 2017 16:05:31 +0900	[thread overview]
Message-ID: <29b6baba-c83b-7591-f2e5-0fb0de609857@daenzer.net> (raw)
In-Reply-To: <20170221100059.GD17643@sill.h.stcim.de>

On 21/02/17 07:00 PM, Stefan Lengfeld wrote:
> 
> 2/ Wait for a single vsync event on all active crtcs as Ville Syrjälä 
>    described here [2] in the optimal implementation.

FWIW, this seems like a bad idea, since with multiple active CRTCs it
would make it essentially random at which intervals the ioctl returns,
and which CRTCs are in vertical blank when it does. So it would be
useless for both timing and tearing prevention purposes, i.e. more or
less completely useless.


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

WARNING: multiple messages have this Message-ID (diff)
From: "Michel Dänzer" <michel@daenzer.net>
To: Stefan Lengfeld <contact@stefanchrist.eu>,
	Maxime Ripard <maxime.ripard@free-electrons.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>,
	linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org
Subject: Re: [PATCH v3 2/2] drm/fb-helper: implement ioctl FBIO_WAITFORVSYNC
Date: Wed, 22 Feb 2017 16:05:31 +0900	[thread overview]
Message-ID: <29b6baba-c83b-7591-f2e5-0fb0de609857@daenzer.net> (raw)
In-Reply-To: <20170221100059.GD17643@sill.h.stcim.de>

On 21/02/17 07:00 PM, Stefan Lengfeld wrote:
> 
> 2/ Wait for a single vsync event on all active crtcs as Ville Syrjälä 
>    described here [2] in the optimal implementation.

FWIW, this seems like a bad idea, since with multiple active CRTCs it
would make it essentially random at which intervals the ioctl returns,
and which CRTCs are in vertical blank when it does. So it would be
useless for both timing and tearing prevention purposes, i.e. more or
less completely useless.


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer
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https://lists.freedesktop.org/mailman/listinfo/dri-devel

  parent reply	other threads:[~2017-02-22  7:05 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-02-15 16:19 [PATCH v3 0/2] drm: Support framebuffer panning Maxime Ripard
2017-02-15 16:19 ` Maxime Ripard
2017-02-15 16:19 ` [PATCH v3 1/2] drm/fb-helper: Add multi buffer support for cma fbdev Maxime Ripard
2017-02-15 16:19   ` Maxime Ripard
2017-02-20 17:07   ` Stefan Lengfeld
2017-02-23  0:49     ` Maxime Ripard
2017-02-23  0:49       ` Maxime Ripard
2017-02-26 21:06       ` Daniel Vetter
2017-02-15 16:19 ` [PATCH v3 2/2] drm/fb-helper: implement ioctl FBIO_WAITFORVSYNC Maxime Ripard
2017-02-15 16:19   ` Maxime Ripard
2017-02-21 10:00   ` Stefan Lengfeld
2017-02-21 10:00     ` Stefan Lengfeld
2017-02-21 10:55     ` Ville Syrjälä
2017-02-21 10:55       ` Ville Syrjälä
2017-02-23  0:52       ` Maxime Ripard
2017-02-23  0:52         ` Maxime Ripard
2017-02-23  9:02         ` Stefan Lengfeld
2017-02-26 21:11           ` Daniel Vetter
2017-02-22  7:05     ` Michel Dänzer [this message]
2017-02-22  7:05       ` Michel Dänzer
2017-02-16 16:40 ` [PATCH v3 0/2] drm: Support framebuffer panning Neil Armstrong
2017-02-16 16:40   ` Neil Armstrong
2017-02-16 16:40   ` Neil Armstrong

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