Hi Laurent
On Tue, 5 Apr 2011, Laurent Pinchart wrote:
> Hi Guennadi,
>
> On Friday 01 April 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.
>
> [snip]
>
> > 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
>
> [snip]
>
> > @@ -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);
>
> Why only when create->size is > 0 ?
Because otherwise create->format contains the frame format, that will be
used for plane-size calculations.
> > + 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)
>
> Shouldn't cache management be handled at submit/qbuf time instead of being a
> buffer property ?
hmm, I'd prefer fixing it at create. Or do you want to be able to create
buffers and then submit / queue them with different flags?...
> > +/* 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 */
> > + struct v4l2_format format; /* "type" is used always, the rest if size
> ==
> > 0 */ +};
>
> You need reserved fields here.
Yes, already discussed with Hans, will add.
>
> > +
> > /*
> > * 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)
>
> Just throwing an idea in here, what about using the same structure for both
> ioctls ? Or even a single ioctl for both create and destroy, like we do with
> REQBUFS ?
Personally, tbh, I don't like either of them. The first one seems an
overkill - you don't need all those fields for destroy. The second one is
a particular case of the first one, plus it adds confusion by re-using the
ioctl:-) Where with REQBUFS we could just set count = 0 to say - release
all buffers, with this one we need index and count, so, we'd need one more
flag to distinguish between create / destroy...
> > +#define VIDIOC_SUBMIT_BUF _IOW('V', 94, int)
> > +
> > /* Reminder: when adding new ioctls please add support for them to
> > drivers/media/video/v4l2-compat-ioctl32.c as well! */
> >
>
> [snip]
>
> --
> Regards,
>
> Laurent Pinchart
Thanks
Guennadi
---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
http://www.open-technology.de/
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