Re: [PATCH] [media] v4l: vb2-dma-contig: add support for file access mode flags for DMABUF exporting

[Philipp Zabel <p.zabel@pengutronix.de>]

Am Mittwoch, den 11.09.2013, 11:56 +0200 schrieb Sylwester Nawrocki:
> Tomasz, Marek,
> 
> Can you review/ack this patch ? I can't see nothing wrong in it and
> it has been sat on the ML for quite long. I would add it to my pull
> request once it is reviewed.
> 
> Thanks,
> Sylwester

Ping?

This patch is needed to map videobuf2 exported dmabuf fds writeable from
userspace, for example for timestamp software rendering into frames
passing from a v4l2 capture device to a v4l2 output device.

regards
Philipp

> On 05/21/2013 10:11 AM, Philipp Zabel wrote:
> > Currently it is not possible for userspace to map a DMABUF exported buffer
> > with write permissions. This patch allows to also pass O_RDONLY/O_RDWR when
> > exporting the buffer, so that userspace may map it with write permissions.
> > 
> > Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
> > ---
> >  Documentation/DocBook/media/v4l/vidioc-expbuf.xml | 8 +++++---
> >  drivers/media/v4l2-core/videobuf2-core.c          | 8 ++++----
> >  drivers/media/v4l2-core/videobuf2-dma-contig.c    | 4 ++--
> >  include/media/videobuf2-core.h                    | 2 +-
> >  4 files changed, 12 insertions(+), 10 deletions(-)
> > 
> > diff --git a/Documentation/DocBook/media/v4l/vidioc-expbuf.xml b/Documentation/DocBook/media/v4l/vidioc-expbuf.xml
> > index e287c8f..4165e7b 100644
> > --- a/Documentation/DocBook/media/v4l/vidioc-expbuf.xml
> > +++ b/Documentation/DocBook/media/v4l/vidioc-expbuf.xml
> > @@ -73,7 +73,8 @@ range from zero to the maximal number of valid planes for the currently active
> >  format. For the single-planar API, applications must set <structfield> plane
> >  </structfield> to zero.  Additional flags may be posted in the <structfield>
> >  flags </structfield> field.  Refer to a manual for open() for details.
> > -Currently only O_CLOEXEC is supported.  All other fields must be set to zero.
> > +Currently only O_CLOEXEC, O_RDONLY, O_WRONLY, and O_RDWR are supported.  All
> > +other fields must be set to zero.
> >  In the case of multi-planar API, every plane is exported separately using
> >  multiple <constant> VIDIOC_EXPBUF </constant> calls. </para>
> >  
> > @@ -170,8 +171,9 @@ multi-planar API. Otherwise this value must be set to zero. </entry>
> >  	    <entry>__u32</entry>
> >  	    <entry><structfield>flags</structfield></entry>
> >  	    <entry>Flags for the newly created file, currently only <constant>
> > -O_CLOEXEC </constant> is supported, refer to the manual of open() for more
> > -details.</entry>
> > +O_CLOEXEC </constant>, <constant>O_RDONLY</constant>, <constant>O_WRONLY
> > +</constant>, and <constant>O_RDWR</constant> are supported, refer to the manual
> > +of open() for more details.</entry>
> >  	  </row>
> >  	  <row>
> >  	    <entry>__s32</entry>
> > diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
> > index 7d833ee..5f7ae44 100644
> > --- a/drivers/media/v4l2-core/videobuf2-core.c
> > +++ b/drivers/media/v4l2-core/videobuf2-core.c
> > @@ -1785,8 +1785,8 @@ int vb2_expbuf(struct vb2_queue *q, struct v4l2_exportbuffer *eb)
> >  		return -EINVAL;
> >  	}
> >  
> > -	if (eb->flags & ~O_CLOEXEC) {
> > -		dprintk(1, "Queue does support only O_CLOEXEC flag\n");
> > +	if (eb->flags & ~(O_CLOEXEC | O_ACCMODE)) {
> > +		dprintk(1, "Queue does support only O_CLOEXEC and access mode flags\n");
> >  		return -EINVAL;
> >  	}
> >  
> > @@ -1809,14 +1809,14 @@ int vb2_expbuf(struct vb2_queue *q, struct v4l2_exportbuffer *eb)
> >  
> >  	vb_plane = &vb->planes[eb->plane];
> >  
> > -	dbuf = call_memop(q, get_dmabuf, vb_plane->mem_priv);
> > +	dbuf = call_memop(q, get_dmabuf, vb_plane->mem_priv, eb->flags & O_ACCMODE);
> >  	if (IS_ERR_OR_NULL(dbuf)) {
> >  		dprintk(1, "Failed to export buffer %d, plane %d\n",
> >  			eb->index, eb->plane);
> >  		return -EINVAL;
> >  	}
> >  
> > -	ret = dma_buf_fd(dbuf, eb->flags);
> > +	ret = dma_buf_fd(dbuf, eb->flags & ~O_ACCMODE);
> >  	if (ret < 0) {
> >  		dprintk(3, "buffer %d, plane %d failed to export (%d)\n",
> >  			eb->index, eb->plane, ret);
> > diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c
> > index fd56f25..e443df5 100644
> > --- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
> > +++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c
> > @@ -393,7 +393,7 @@ static struct sg_table *vb2_dc_get_base_sgt(struct vb2_dc_buf *buf)
> >  	return sgt;
> >  }
> >  
> > -static struct dma_buf *vb2_dc_get_dmabuf(void *buf_priv)
> > +static struct dma_buf *vb2_dc_get_dmabuf(void *buf_priv, unsigned long flags)
> >  {
> >  	struct vb2_dc_buf *buf = buf_priv;
> >  	struct dma_buf *dbuf;
> > @@ -404,7 +404,7 @@ static struct dma_buf *vb2_dc_get_dmabuf(void *buf_priv)
> >  	if (WARN_ON(!buf->sgt_base))
> >  		return NULL;
> >  
> > -	dbuf = dma_buf_export(buf, &vb2_dc_dmabuf_ops, buf->size, 0);
> > +	dbuf = dma_buf_export(buf, &vb2_dc_dmabuf_ops, buf->size, flags);
> >  	if (IS_ERR(dbuf))
> >  		return NULL;
> >  
> > diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
> > index d88a098..41709a8 100644
> > --- a/include/media/videobuf2-core.h
> > +++ b/include/media/videobuf2-core.h
> > @@ -83,7 +83,7 @@ struct vb2_fileio_data;
> >  struct vb2_mem_ops {
> >  	void		*(*alloc)(void *alloc_ctx, unsigned long size, gfp_t gfp_flags);
> >  	void		(*put)(void *buf_priv);
> > -	struct dma_buf *(*get_dmabuf)(void *buf_priv);
> > +	struct dma_buf *(*get_dmabuf)(void *buf_priv, unsigned long flags);
> >  
> >  	void		*(*get_userptr)(void *alloc_ctx, unsigned long vaddr,
> >  					unsigned long size, int write);
> > 
> 
>