Messages in this thread | | | Date | Wed, 7 Feb 2024 17:35:26 +0100 | Subject | Re: [PATCH v19 0/9] Add DELETE_BUF ioctl | From | Benjamin Gaignard <> |
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Le 07/02/2024 à 12:32, Hans Verkuil a écrit : > On 07/02/2024 12:25, Benjamin Gaignard wrote: >> 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. > How about VIDIOC_ADD_BUFS/REMOVE_BUFS? > > And struct v4l2_add_bufs/v4l2_remove_bufs.
I'm really bad from naming thing like that. I will until the next and, if nobody complain, I will change my code to use your proposal.
Regards, Benjamin
> > One thing that I always found debatable about the names CREATE and DELETE > is that it suggests that buffer memory is also created and deleted. While > true for MMAP, that's not the case for DMABUF and USERPTR. > > Regards, > > Hans > >> Regards, >> Benjamin >> >>> Ideas are welcome. >>> >>> Regards, >>> >>> Hans >>>
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