From: Nicolas Dufresne <nicolas@ndufresne.ca>
To: Brian Starkey <brian.starkey@arm.com>, Hans Verkuil <hverkuil@xs4all.nl>
Cc: Daniel Vetter <daniel@ffwll.ch>,
"linux-media@vger.kernel.org" <linux-media@vger.kernel.org>,
jonathan.chai@arm.com,
Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
dri-devel <dri-devel@lists.freedesktop.org>
Subject: Re: DRM Format Modifiers in v4l2
Date: Mon, 28 Aug 2017 14:07:22 -0400 [thread overview]
Message-ID: <1503943642.3316.7.camel@ndufresne.ca> (raw)
In-Reply-To: <20170824122647.GA28829@e107564-lin.cambridge.arm.com>
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Le jeudi 24 août 2017 à 13:26 +0100, Brian Starkey a écrit :
> > What I mean was: an application can use the modifier to give buffers from
> > one device to another without needing to understand it.
> >
> > But a generic video capture application that processes the video itself
> > cannot be expected to know about the modifiers. It's a custom HW specific
> > format that you only use between two HW devices or with software written
> > for that hardware.
> >
>
> Yes, makes sense.
>
> > >
> > > However, in DRM the API lets you get the supported formats for each
> > > modifier as-well-as the modifier list itself. I'm not sure how exactly
> > > to provide that in a control.
> >
> > We have support for a 'menu' of 64 bit integers: V4L2_CTRL_TYPE_INTEGER_MENU.
> > You use VIDIOC_QUERYMENU to enumerate the available modifiers.
> >
> > So enumerating these modifiers would work out-of-the-box.
>
> Right. So I guess the supported set of formats could be somehow
> enumerated in the menu item string. In DRM the pairs are (modifier +
> bitmask) where bits represent formats in the supported formats list
> (commit db1689aa61bd in drm-next). Printing a hex representation of
> the bitmask would be functional but I concede not very pretty.
The problem is that the list of modifiers depends on the format
selected. Having to call S_FMT to obtain this list is quite
inefficient.
Also, be aware that DRM_FORMAT_MOD_SAMSUNG_64_32_TILE modifier has been
implemented in V4L2 with a direct format (V4L2_PIX_FMT_NV12MT). I think
an other one made it the same way recently, something from Mediatek if
I remember. Though, unlike the Intel one, the same modifier does not
have various result depending on the hardware revision.
regards,
Nicolas
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next prev parent reply other threads:[~2017-08-28 18:07 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-21 15:52 DRM Format Modifiers in v4l2 Brian Starkey
2017-08-21 16:01 ` Daniel Vetter
2017-08-21 16:21 ` Brian Starkey
2017-08-21 16:36 ` Hans Verkuil
2017-08-24 11:14 ` Brian Starkey
2017-08-24 11:37 ` Hans Verkuil
2017-08-24 12:26 ` Brian Starkey
2017-08-25 8:14 ` Hans Verkuil
2017-08-29 9:19 ` Brian Starkey
2017-08-31 14:36 ` Laurent Pinchart
2017-08-28 18:07 ` Nicolas Dufresne [this message]
2017-08-28 20:49 ` Daniel Vetter
2017-08-29 9:47 ` Brian Starkey
2017-08-30 7:50 ` Daniel Vetter
2017-08-30 8:10 ` Hans Verkuil
2017-08-30 9:36 ` Brian Starkey
2017-08-30 9:53 ` Hans Verkuil
2017-08-30 10:32 ` Brian Starkey
2017-08-31 14:51 ` Laurent Pinchart
2017-08-31 15:23 ` Brian Starkey
2017-08-31 14:28 ` Laurent Pinchart
2017-08-31 16:12 ` Nicolas Dufresne
2017-09-01 7:13 ` Laurent Pinchart
2017-09-01 12:43 ` Rob Clark
2017-09-03 9:00 ` Daniel Vetter
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