Messages in this thread | ![/](/images/icornerl.gif) | | Date | Wed, 7 Feb 2024 12:25:08 +0100 | Subject | Re: [PATCH v19 0/9] Add DELETE_BUF ioctl | From | Benjamin Gaignard <> |
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Le 07/02/2024 à 11:28, Hans Verkuil a écrit : > On 06/02/2024 09:58, Hans Verkuil wrote: >> On 06/02/2024 09:02, Benjamin Gaignard wrote: >>> Unlike when resolution change on keyframes, dynamic resolution change >>> on inter frames doesn't allow to do a stream off/on sequence because >>> it is need to keep all previous references alive to decode inter frames. >>> This constraint have two main problems: >>> - more memory consumption. >>> - more buffers in use. >>> To solve these issue this series introduce DELETE_BUFS ioctl and remove >>> the 32 buffers limit per queue. >> This v19 looks good. There are three outstanding issues that I need to take a >> look at: >> >> 1) Can we still signal support for DELETE_BUFS in the V4L2_BUF_CAP_ caps? >> It would be nice to have, but I'm not sure if and how that can be done. >> >> 2) I want to take another look at providing a next version of the VIDIOC_CREATE_BUFS >> ioctl and how that would possibly influence the design of DELETE_BUFS. >> Just to make sure we're not blocking anything or making life harder. > So I just tried creating a new version of the VIDIOC_CREATE_BUFS ioctl > that is greatly simplified. This just updates the header, no real code yet: > > Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> > --- > diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h > index 03443833aaaa..a7398e4c85e7 100644 > --- a/include/uapi/linux/videodev2.h > +++ b/include/uapi/linux/videodev2.h > @@ -2624,6 +2624,39 @@ struct v4l2_create_buffers { > __u32 reserved[5]; > }; > > +/** > + * struct v4l2_create_buffers_v2 - VIDIOC_CREATE_BUFFERS argument > + * @type: enum v4l2_buf_type > + * @memory: enum v4l2_memory; buffer memory type > + * @count: entry: number of requested buffers, > + * return: number of created buffers > + * @num_planes: requested number of planes for each buffer > + * @sizes: requested plane sizes for each buffer > + * @start_index:on return, index of the first created buffer > + * @total_count:on return, the total number of allocated buffers > + * @capabilities: capabilities of this buffer type. > + * @flags: additional buffer management attributes (ignored unless the > + * queue has V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS capability > + * and configured for MMAP streaming I/O). > + * @max_num_buffers: if V4L2_BUF_CAP_SUPPORTS_MAX_NUM_BUFFERS capability flag is set > + * this field indicate the maximum possible number of buffers > + * for this queue. > + * @reserved: future extensions > + */ > +struct v4l2_create_buffers_v2 { > + __u32 type; > + __u32 memory; > + __u32 count; > + __u32 num_planes; > + __u32 size[VIDEO_MAX_PLANES]; > + __u32 start_index; > + __u32 total_count; > + __u32 capabilities; > + __u32 flags; > + __u32 max_num_buffers; > + __u32 reserved[7]; > +}; > + > /** > * struct v4l2_delete_buffers - VIDIOC_DELETE_BUFS argument > * @index: the first buffer to be deleted > @@ -2738,6 +2771,7 @@ struct v4l2_delete_buffers { > > #define VIDIOC_QUERY_EXT_CTRL _IOWR('V', 103, struct v4l2_query_ext_ctrl) > #define VIDIOC_DELETE_BUFS _IOWR('V', 104, struct v4l2_delete_buffers) > +#define VIDIOC_CREATE_BUFFERS _IOWR('V', 105, struct v4l2_create_buffers_v2) > > > /* Reminder: when adding new ioctls please add support for them to > > > Sadly, struct v4l2_create_buffers was already used for the existing > VIDIOC_CREATE_BUFS (I wish it was called v4l2_create_bufs...), so I did > have to add a _v2 suffix. Compared to the old struct it just moves the > type, num_planes and sizes from v4l2_format into the new struct and drops > the format field. Note that those fields are the only v4l2_format fields > that VIDIOC_CREATE_BUFS used, so getting rid of the format makes live > much easier. I also renamed 'index' to 'start_index' and added a new 'total_count' > field to report the total number of buffers. > > The reason for adding 'total_count' is that VIDIOC_CREATE_BUFS with > count == 0 would report the total number of buffers in the 'index' field, > which was rather odd. Adding a specific field for this purpose is nicer. > > One thing that might impact your series is the name of the ioctls. > > We have: > > VIDIOC_CREATE_BUFS/v4l2_create_buffers > VIDIOC_DELETE_BUFS/v4l2_delete_buffers > VIDIOC_CREATE_BUFFERS/v4l2_create_buffers_v2 (TBD) > > I'm wondering if VIDIOC_DELETE_BUFS should be renamed to > VIDIOC_DELETE_BUFFERS, that would make it more consistent with > the proposed VIDIOC_CREATE_BUFFERS. > > Alternatively, instead of calling it VIDIOC_CREATE_BUFFERS we > might call it VIDIOC_CREATE_BUFS_V2. > > Or perhaps some other naming convention?
Maybe VIDIOC_NEW_BUFS/v4l2_new_buffers ?
I will wait until naming convention is fixed before send v20.
Regards, Benjamin
> > Ideas are welcome. > > Regards, > > Hans >
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