linux-kernel - Re: [PATCH v2 03/15] media: videobuf2: Allow exporting of a struct dmabuf

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Message-ID: <20231115193107.GB29486@pendragon.ideasonboard.com>
Date:   Wed, 15 Nov 2023 21:31:07 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Stefan Wahren <wahrenst@....net>
Cc:     Umang Jain <umang.jain@...asonboard.com>,
        linux-media@...r.kernel.org, kernel-list@...pberrypi.com,
        linux-kernel@...r.kernel.org, linux-rpi-kernel@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-staging@...ts.linux.dev,
        Dave Stevenson <dave.stevenson@...pberrypi.com>,
        Kieran Bingham <kieran.bingham@...asonboard.com>,
        "Ricardo B . Marliere" <ricardo@...liere.net>,
        Dan Carpenter <error27@...il.com>,
        Dave Stevenson <dave.stevenson@...pberrypi.org>
Subject: Re: [PATCH v2 03/15] media: videobuf2: Allow exporting of a struct
 dmabuf

On Tue, Nov 14, 2023 at 08:41:11PM +0100, Stefan Wahren wrote:
> Am 09.11.23 um 22:02 schrieb Umang Jain:
> > From: Dave Stevenson <dave.stevenson@...pberrypi.org>
> >
> > videobuf2 only allowed exporting a dmabuf as a file descriptor,
> > but there are instances where having the struct dma_buf is
> > useful within the kernel.
> >
> > Split the current implementation into two, one step which
> > exports a struct dma_buf, and the second which converts that
> > into an fd.
> >
> > Signed-off-by: Dave Stevenson <dave.stevenson@...pberrypi.org>
> > Signed-off-by: Umang Jain <umang.jain@...asonboard.com>
> > ---
> 
> ...
> 
> > diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
> > index 4b6a9d2ea372..cba4e495f6a2 100644
> > --- a/include/media/videobuf2-core.h
> > +++ b/include/media/videobuf2-core.h
> > @@ -925,6 +925,21 @@ int vb2_core_streamon(struct vb2_queue *q, unsigned int type);
> >    */
> >   int vb2_core_streamoff(struct vb2_queue *q, unsigned int type);
> >
> > +/**
> > + * vb2_core_expbuf_dmabuf() - Export a buffer as a dma_buf structure
> > + * @q:         videobuf2 queue
> > + * @type:      buffer type
> > + * @index:     id number of the buffer
> > + * @plane:     index of the plane to be exported, 0 for single plane queues
> > + * @flags:     flags for newly created file, currently only O_CLOEXEC is
> > + *             supported, refer to manual of open syscall for more details
> 
> i think "newly created file" could be confusing here

Would "newly created dmabuf file handle" be clearer and work for
everybody ?

> > + *
> > + * Return: Returns the dmabuf pointer
> > + */
> > +struct dma_buf *vb2_core_expbuf_dmabuf(struct vb2_queue *q, unsigned int type,
> > +				       unsigned int index, unsigned int plane,
> > +				       unsigned int flags);
> > +
> >   /**
> >    * vb2_core_expbuf() - Export a buffer as a file descriptor.
> >    * @q:		pointer to &struct vb2_queue with videobuf2 queue.

-- 
Regards,

Laurent Pinchart