Hi Hans
On Wed, 28 Sep 2011, Hans Verkuil wrote:
> On Tuesday, September 27, 2011 18:54:53 Guennadi Liakhovetski wrote:
> > A possibility to preallocate and initialise buffers of different sizes
> > in V4L2 is required for an efficient implementation of a snapshot
> > mode. This patch adds two new ioctl()s: VIDIOC_CREATE_BUFS and
> > VIDIOC_PREPARE_BUF and defines respective data structures.
> >
> > Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@xxxxxx>
> > ---
> >
> > v8: addressed comments from Hans - thanks:
> >
> > 1. added checks in ioctl() preprocessing
> > 2. changed VIDIOC_PREPARE_BUF to _IOWR
> >
> > drivers/media/video/v4l2-compat-ioctl32.c | 67 +++++++++++++++++++++++++---
> > drivers/media/video/v4l2-ioctl.c | 36 +++++++++++++++
> > include/linux/videodev2.h | 17 +++++++
> > include/media/v4l2-ioctl.h | 2 +
> > 4 files changed, 114 insertions(+), 8 deletions(-)
> >
>
> Almost:
>
> > diff --git a/include/linux/videodev2.h b/include/linux/videodev2.h
> > index 9d14523..7d75dd1 100644
> > --- a/include/linux/videodev2.h
> > +++ b/include/linux/videodev2.h
> > @@ -653,6 +653,9 @@ struct v4l2_buffer {
> > #define V4L2_BUF_FLAG_ERROR 0x0040
> > #define V4L2_BUF_FLAG_TIMECODE 0x0100 /* timecode field is valid */
> > #define V4L2_BUF_FLAG_INPUT 0x0200 /* input field is valid */
> > +/* Cache handling flags */
> > +#define V4L2_BUF_FLAG_NO_CACHE_INVALIDATE 0x0400
> > +#define V4L2_BUF_FLAG_NO_CACHE_CLEAN 0x0800
> >
> > /*
> > * O V E R L A Y P R E V I E W
> > @@ -2099,6 +2102,15 @@ struct v4l2_dbg_chip_ident {
> > __u32 revision; /* chip revision, chip specific */
> > } __attribute__ ((packed));
> >
> > +/* VIDIOC_CREATE_BUFS */
> > +struct v4l2_create_buffers {
> > + __u32 index; /* output: buffers index...index + count - 1 have been created */
> > + __u32 count;
> > + enum v4l2_memory memory;
> > + struct v4l2_format format; /* "type" is used always, the rest if sizeimage == 0 */
> > + __u32 reserved[8];
> > +};
> > +
> > /*
> > * I O C T L C O D E S F O R V I D E O D E V I C E S
> > *
> > @@ -2189,6 +2201,11 @@ struct v4l2_dbg_chip_ident {
> > #define VIDIOC_SUBSCRIBE_EVENT _IOW('V', 90, struct v4l2_event_subscription)
> > #define VIDIOC_UNSUBSCRIBE_EVENT _IOW('V', 91, struct v4l2_event_subscription)
> >
> > +/* Experimental, the below two ioctls may change over the next couple of kernel
> > + versions */
> > +#define VIDIOC_CREATE_BUFS _IOWR('V', 92, struct v4l2_create_buffers)
> > +#define VIDIOC_PREPARE_BUF _IOWR('V', 93, struct v4l2_buffer)
> > +
> > /* Reminder: when adding new ioctls please add support for them to
> > drivers/media/video/v4l2-compat-ioctl32.c as well! */
> >
> > diff --git a/include/media/v4l2-ioctl.h b/include/media/v4l2-ioctl.h
> > index dd9f1e7..55cf8ae 100644
> > --- a/include/media/v4l2-ioctl.h
> > +++ b/include/media/v4l2-ioctl.h
> > @@ -122,6 +122,8 @@ struct v4l2_ioctl_ops {
> > int (*vidioc_qbuf) (struct file *file, void *fh, struct v4l2_buffer *b);
> > int (*vidioc_dqbuf) (struct file *file, void *fh, struct v4l2_buffer *b);
> >
> > + int (*vidioc_create_bufs)(struct file *file, void *fh, struct v4l2_create_buffers *b);
> > + int (*vidioc_prepare_buf)(struct file *file, void *fh, const struct v4l2_buffer *b);
>
> If this is IOWR, then there shouldn't be a const here.
hrm... Sure.
> I have been thinking about this a bit more. Currently we only have a V4L2_BUF_FLAG_QUEUED
> flag and no V4L2_BUF_FLAG_PREPARED flag. I do think we need this after all. The QUEUED flag
> can't be used here as the buffer isn't queued yet, it's only prepared.
Ok, I can add it to this patch together with the other two cache-handling
flags. I presume, I shall also add it to
V4L2_BUFFER_STATE_FLAGS
in videobuf2-core.c, otherwise just let drivers and apps go figure?... We
could set that flag centrally in __buf_prepare(), but since
V4L2_BUF_FLAG_QUEUED is managed by individual drivers, we probably want to
leave V4L2_BUF_FLAG_PREPARED like that too?
Thanks
Guennadi
>
> Regards,
>
> Hans
>
> >
> > int (*vidioc_overlay) (struct file *file, void *fh, unsigned int i);
> > int (*vidioc_g_fbuf) (struct file *file, void *fh,
> >
>
---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
http://www.open-technology.de/
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