Re: [RFC 2/4] media: videobuf2: Replace bufs array by a list

From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: Nicolas Dufresne <nicolas@ndufresne.ca>
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Subject: Re: [RFC 2/4] media: videobuf2: Replace bufs array by a list
Date: Wed, 22 Mar 2023 17:01:53 +0200	[thread overview]
Message-ID: <20230322150153.GO20234@pendragon.ideasonboard.com> (raw)
In-Reply-To: <f085aa9225c573df906bdc7ff032a8fd591b18b3.camel@ndufresne.ca>

On Wed, Mar 22, 2023 at 10:50:52AM -0400, Nicolas Dufresne wrote:
> Hi Laurent,
> 
> Le lundi 20 mars 2023 à 01:33 +0200, Laurent Pinchart a écrit :
> > > The typical usage is that applications allocate N buffers with the
> > > VIDIOC_REQBUFS ioctl, and in most cases that's all they use.
> > 
> > Note that once we get DELETE_BUF (or DELETE_BUFS) support I'd like to
> > encourage applications to use the new API, and deprecate REQBUFS
> > (dropping it isn't on my radar, as it would take forever before no
> > userspace uses it anymore).
> 
> I was wondering if you can extend on this. I'm worried the count semantic might
> prevent emulating it over create_bufs() ops, but if that works, did you meant to
> emulate it so driver no longer have to implement reqbufs() if they have
> create_bufs() ?

For drivers it should be fairly simply, as the reqbufs and create_bufs
ioctl handlers should just point to the corresponding videobuf2 helpers.

What I meant is that I'd like to encourage userspace to use the
VIDIOC_CREATE_BUFS ioctl instead of VIDIOC_REQBUFS.

-- 
Regards,

Laurent Pinchart