Hi Hans
Thanks for the review
On Mon, 4 Apr 2011, Hans Verkuil wrote:
> On Friday, April 01, 2011 10:13:02 Guennadi Liakhovetski wrote:
> > A possibility to preallocate and initialise buffers of different sizes
> > in V4L2 is required for an efficient implementation of asnapshot mode.
> > This patch adds three new ioctl()s: VIDIOC_CREATE_BUFS,
> > VIDIOC_DESTROY_BUFS, and VIDIOC_SUBMIT_BUF and defines respective data
> > structures.
> >
> > Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@xxxxxx>
> > ---
> > drivers/media/video/v4l2-compat-ioctl32.c | 3 ++
> > drivers/media/video/v4l2-ioctl.c | 43 +++++++++++++++++++++++++++++
> > include/linux/videodev2.h | 24 ++++++++++++++++
> > include/media/v4l2-ioctl.h | 3 ++
> > 4 files changed, 73 insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/media/video/v4l2-compat-ioctl32.c b/drivers/media/video/v4l2-compat-ioctl32.c
> > index 7c26947..d71b289 100644
> > --- a/drivers/media/video/v4l2-compat-ioctl32.c
> > +++ b/drivers/media/video/v4l2-compat-ioctl32.c
> > @@ -922,6 +922,9 @@ long v4l2_compat_ioctl32(struct file *file, unsigned int cmd, unsigned long arg)
> > case VIDIOC_DQEVENT:
> > case VIDIOC_SUBSCRIBE_EVENT:
> > case VIDIOC_UNSUBSCRIBE_EVENT:
> > + case VIDIOC_CREATE_BUFS:
> > + case VIDIOC_DESTROY_BUFS:
> > + case VIDIOC_SUBMIT_BUF:
> > ret = do_video_ioctl(file, cmd, arg);
> > break;
> >
> > diff --git a/drivers/media/video/v4l2-ioctl.c b/drivers/media/video/v4l2-ioctl.c
> > index a01ed39..b80a211 100644
> > --- a/drivers/media/video/v4l2-ioctl.c
> > +++ b/drivers/media/video/v4l2-ioctl.c
> > @@ -259,6 +259,9 @@ static const char *v4l2_ioctls[] = {
> > [_IOC_NR(VIDIOC_DQEVENT)] = "VIDIOC_DQEVENT",
> > [_IOC_NR(VIDIOC_SUBSCRIBE_EVENT)] = "VIDIOC_SUBSCRIBE_EVENT",
> > [_IOC_NR(VIDIOC_UNSUBSCRIBE_EVENT)] = "VIDIOC_UNSUBSCRIBE_EVENT",
> > + [_IOC_NR(VIDIOC_CREATE_BUFS)] = "VIDIOC_CREATE_BUFS",
> > + [_IOC_NR(VIDIOC_DESTROY_BUFS)] = "VIDIOC_DESTROY_BUFS",
> > + [_IOC_NR(VIDIOC_SUBMIT_BUF)] = "VIDIOC_SUBMIT_BUF",
> > };
> > #define V4L2_IOCTLS ARRAY_SIZE(v4l2_ioctls)
> >
> > @@ -2184,6 +2187,46 @@ static long __video_do_ioctl(struct file *file,
> > dbgarg(cmd, "type=0x%8.8x", sub->type);
> > break;
> > }
> > + case VIDIOC_CREATE_BUFS:
> > + {
> > + struct v4l2_create_buffers *create = arg;
> > +
> > + if (!ops->vidioc_create_bufs)
> > + break;
> > + ret = check_fmt(ops, create->format.type);
> > + if (ret)
> > + break;
> > +
> > + if (create->size)
> > + CLEAR_AFTER_FIELD(create, count);
> > +
> > + ret = ops->vidioc_create_bufs(file, fh, create);
> > +
> > + dbgarg(cmd, "count=%d\n", create->count);
> > + break;
> > + }
> > + case VIDIOC_DESTROY_BUFS:
> > + {
> > + struct v4l2_buffer_span *span = arg;
> > +
> > + if (!ops->vidioc_destroy_bufs)
> > + break;
> > +
> > + ret = ops->vidioc_destroy_bufs(file, fh, span);
> > +
> > + dbgarg(cmd, "count=%d", span->count);
> > + break;
> > + }
> > + case VIDIOC_SUBMIT_BUF:
> > + {
> > + unsigned int *i = arg;
> > +
> > + if (!ops->vidioc_submit_buf)
> > + break;
> > + ret = ops->vidioc_submit_buf(file, fh, *i);
> > + dbgarg(cmd, "index=%d", *i);
> > + break;
> > + }
> > default:
> > {
> > bool valid_prio = true;
> > diff --git a/include/linux/videodev2.h b/include/linux/videodev2.h
> > index aa6c393..b6ef46e 100644
> > --- a/include/linux/videodev2.h
> > +++ b/include/linux/videodev2.h
> > @@ -1847,6 +1847,26 @@ struct v4l2_dbg_chip_ident {
> > __u32 revision; /* chip revision, chip specific */
> > } __attribute__ ((packed));
> >
> > +/* VIDIOC_DESTROY_BUFS */
> > +struct v4l2_buffer_span {
> > + __u32 index; /* output: buffers index...index + count - 1 have been created */
> > + __u32 count;
> > + __u32 reserved[2];
> > +};
> > +
> > +/* struct v4l2_createbuffers::flags */
> > +#define V4L2_BUFFER_FLAG_NO_CACHE_INVALIDATE (1 << 0)
>
> We also need a FLAG_NO_CACHE_FLUSH. This is for output devices.
Ok.
> > +
> > +/* VIDIOC_CREATE_BUFS */
> > +struct v4l2_create_buffers {
> > + __u32 index; /* output: buffers index...index + count - 1 have been created */
> > + __u32 count;
> > + __u32 flags; /* V4L2_BUFFER_FLAG_* */
> > + enum v4l2_memory memory;
> > + __u32 size; /* Explicit size, e.g., for compressed streams */
>
> Hmm, shouldn't this be an array of size VIDEO_MAX_PLANES?
Not sure. As the comment says, this is mainly for bitstream formats. For
any pixel-based format you really should just fill in the format below. If
you allow the user to specify planes, then you also need to know
alignment, contiguity, padding, etc.
> > + struct v4l2_format format; /* "type" is used always, the rest if size == 0 */
>
> Needs some reserved fields as well.
v4l2_format is a union with 200 bytes, is this not enough?
> > +};
> > +
> > /*
> > * 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
> > *
> > @@ -1937,6 +1957,10 @@ 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)
> >
> > +#define VIDIOC_CREATE_BUFS _IOWR('V', 92, struct v4l2_create_buffers)
> > +#define VIDIOC_DESTROY_BUFS _IOWR('V', 93, struct v4l2_buffer_span)
> > +#define VIDIOC_SUBMIT_BUF _IOW('V', 94, int)
>
> I don't really like the name. I think I'd go for _PRE_QBUF or _PREP_BUF or
> something like that.
I didn't want to use any form of prepare, because we already have a
.buf_prepare() method, and IMHO it would be confusing. Pre-queue I didn't
like very much either, for the same reasons, why we rejected it at the
meeting, which was, I think, that it's not really doing anything with the
queue, right? What this ioctl() does is it passes buffer ownership from
the user-space to the kernel, right? Any good name for that? In fact
"submit" doesn't sound too bad to me:-)
> BTW, I agree with other reviewers that DESTROY_BUFS shouldn't leave any holes.
That was our decision at the meeting - I can well remember that, I was
surprised about that too, so, I think, I even asked to clarify this point.
But we can change it of course. Shall we return -EBUSY if the user is
trying to free buffers in the middle?
> And if CREATE_BUFS has an error, then it shouldn't destroy all buffers, but only
> those that create_bufs managed to allocate before the error occurred.
Sure, that's a bug.
> Regards,
>
> Hans
>
> > +
> > /* Reminder: when adding new ioctls please add support for them to
> > drivers/media/video/v4l2-compat-ioctl32.c as well! */
>
> Don't forget this! VIDIOC_CREATE_BUFS will need to be handled in compat-ioctl32.
I didn't:
> > drivers/media/video/v4l2-compat-ioctl32.c | 3 ++
Or is that not enough? Is any special handling required? AFAICS, REQBUFS
is not treated specially either.
Thanks
Guennadi
> Regards,
>
> Hans
>
> >
> > diff --git a/include/media/v4l2-ioctl.h b/include/media/v4l2-ioctl.h
> > index dd9f1e7..00962c6 100644
> > --- a/include/media/v4l2-ioctl.h
> > +++ b/include/media/v4l2-ioctl.h
> > @@ -122,6 +122,9 @@ 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_destroy_bufs)(struct file *file, void *fh, struct v4l2_buffer_span *b);
> > + int (*vidioc_submit_buf) (struct file *file, void *fh, unsigned int i);
> >
> > 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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