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From: Sakari Ailus <sakari.ailus@linux.intel.com>
To: Hans Verkuil <hverkuil@xs4all.nl>
Cc: Linux Media Mailing List <linux-media@vger.kernel.org>,
	Ezequiel Garcia <ezequiel@collabora.com>,
	Nicolas Dufresne <nicolas@ndufresne.ca>,
	Tomasz Figa <tfiga@chromium.org>
Subject: Re: [PATCH] videodev2.h: add V4L2_BUF_CAP_SUPPORTS_PREPARE_BUF/CREATE_BUFS
Date: Tue, 20 Nov 2018 12:03:10 +0200	[thread overview]
Message-ID: <20181120100310.z5xerjvsf76qqtcd@paasikivi.fi.intel.com> (raw)
In-Reply-To: <8711051e-df50-181f-d5e3-677d63d63465@xs4all.nl>

On Tue, Nov 20, 2018 at 10:41:42AM +0100, Hans Verkuil wrote:
> On 11/20/2018 10:27 AM, Sakari Ailus wrote:
> > Hi Hans,
> > 
> > On Tue, Nov 20, 2018 at 09:58:43AM +0100, Hans Verkuil wrote:
> >> Add new buffer capability flags to indicate if the VIDIOC_PREPARE_BUF or
> >> VIDIOC_CREATE_BUFS ioctls are supported.
> > 
> > Are there practical benefits from the change for the user space?
> 
> The more important ioctl to know about is PREPARE_BUF. I noticed this when working
> on v4l2-compliance: the only way to know for an application if PREPARE_BUF exists
> is by trying it, but then you already have prepared a buffer. That's not what you
> want in the application, you need a way to know up front if prepare_buf is present
> or not without having to actually execute it.
> 
> CREATE_BUFS was added because not all drivers support it. It can be dropped since
> it is possible to test for the existence of CREATE_BUFS without actually allocating
> anything, but if I'm adding V4L2_BUF_CAP_SUPPORTS_PREPARE_BUF anyway, then it is
> trivial to add V4L2_BUF_CAP_SUPPORTS_CREATE_BUFS as well to avoid an additional
> ioctl call.
> 
> Hmm, I should have explained this in the commit log.

Please add:

Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>

-- 
Sakari Ailus
sakari.ailus@linux.intel.com

  reply	other threads:[~2018-11-20 20:31 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-20  8:58 [PATCH] videodev2.h: add V4L2_BUF_CAP_SUPPORTS_PREPARE_BUF/CREATE_BUFS Hans Verkuil
2018-11-20  9:27 ` Sakari Ailus
2018-11-20  9:41   ` Hans Verkuil
2018-11-20 10:03     ` Sakari Ailus [this message]
2018-11-20 11:39 ` kbuild test robot
2018-11-20 11:48 ` kbuild test robot

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