Hi Hans, On Monday 05 Dec 2016 16:02:55 Hans Verkuil wrote: > On 12/05/2016 03:45 PM, Laurent Pinchart wrote: > > On Monday 05 Dec 2016 14:44:55 Hans Verkuil wrote: > >> On 11/25/2016 03:57 PM, Todor Tomov wrote: > >>> These files handle the video device nodes of the camss driver. > >>> > >>> Signed-off-by: Todor Tomov <todor.tomov@xxxxxxxxxx> > >>> --- > >>> > >>> drivers/media/platform/qcom/camss-8x16/video.c | 597 +++++++++++++++++ > >>> drivers/media/platform/qcom/camss-8x16/video.h | 67 +++ > >>> 2 files changed, 664 insertions(+) > >>> create mode 100644 drivers/media/platform/qcom/camss-8x16/video.c > >>> create mode 100644 drivers/media/platform/qcom/camss-8x16/video.h > > > > [snip] > > > >>> +int msm_video_register(struct camss_video *video, struct v4l2_device > >>> *v4l2_dev, > >>> + const char *name) > >>> +{ > >>> + struct media_pad *pad = &video->pad; > >>> + struct video_device *vdev; > >>> + struct vb2_queue *q; > >>> + int ret; > >>> + > >>> + vdev = video_device_alloc(); > >>> + if (vdev == NULL) { > >>> + dev_err(v4l2_dev->dev, "Failed to allocate video > >>> device\n"); > >>> + return -ENOMEM; > >>> + } > >>> + > >>> + video->vdev = vdev; > >>> + > >>> + q = &video->vb2_q; > >>> + q->drv_priv = video; > >>> + q->mem_ops = &vb2_dma_contig_memops; > >>> + q->ops = &msm_video_vb2_q_ops; > >>> + q->type = V4L2_BUF_TYPE_VIDEO_CAPTURE; > >>> + q->io_modes = VB2_MMAP; > >> > >> Add modes VB2_DMABUF and VB2_READ. These are for free, so why not? > >> Especially DMABUF is of course very desirable to have. > > > > I certainly agree with VB2_DMABUF, but I wouldn't expose VB2_READ. read() > > for this kind of device is inefficient and we should encourage userspace > > application to move away from it (and certainly make it very clear that > > new applications should not use read() with this device). > > VB2_READ is very nice when debugging (no need to program a stream I/O > application first) There's at least v4l2-ctl and yavta that can (and should) be used for debugging ;-) > and useful when you want to pipe the video. Except that you lose frame boundaries. It's really a poor man's solution that should never be used in any "real" application. I'd rather add an option to v4l2-ctl to output the video stream to stdout (and/or stderr). > Nobody uses read() in 'regular' applications since it is obviously > inefficient, but I don't see that as a reason not to offer VB2_READ. > > I don't think this is something anyone will ever abuse, Famous last words ;-) > and it is a nice feature to have (and for free as well). -- Regards, Laurent Pinchart -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html