Re: [PATCH] videodev2.h: add V4L2_BUF_CAP_SUPPORTS_PREPARE_BUF/CREATE_BUFS

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



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@xxxxxxxxxxxxxxx>

-- 
Sakari Ailus
sakari.ailus@xxxxxxxxxxxxxxx



[Index of Archives]     [Linux Input]     [Video for Linux]     [Gstreamer Embedded]     [Mplayer Users]     [Linux USB Devel]     [Linux Audio Users]     [Linux Kernel]     [Linux SCSI]     [Yosemite Backpacking]

  Powered by Linux