On 7/21/20 11:30 AM, Stanimir Varbanov wrote:
> Hi Helen,
>
> On 7/21/20 4:54 PM, Helen Koike wrote:
>> Hi,
>>
>> On 7/21/20 8:26 AM, Stanimir Varbanov wrote:
>>>
>>>
>>> On 7/17/20 2:54 PM, Helen Koike wrote:
>>>> From: Hans Verkuil <hans.verkuil@xxxxxxxxx>
>>>>
>>>> Those extended buffer ops have several purpose:
>>>> 1/ Fix y2038 issues by converting the timestamp into an u64 counting
>>>> the number of ns elapsed since 1970
>>>> 2/ Unify single/multiplanar handling
>>>> 3/ Add a new start offset field to each v4l2 plane buffer info struct
>>>> to support the case where a single buffer object is storing all
>>>> planes data, each one being placed at a different offset
>>>>
>>>> New hooks are created in v4l2_ioctl_ops so that drivers can start using
>>>> these new objects.
>>>>
>>>> The core takes care of converting new ioctls requests to old ones
>>>> if the driver does not support the new hooks, and vice versa.
>>>>
>>>> Note that the timecode field is gone, since there doesn't seem to be
>>>> in-kernel users. We can be added back in the reserved area if needed or
>>>> use the Request API to collect more metadata information from the
>>>> frame.
>>>>
>>>> Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
>>>> Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
>>>> Signed-off-by: Helen Koike <helen.koike@xxxxxxxxxxxxx>
>>>> ---
>>>> Changes in v4:
>>>> - Use v4l2_ext_pix_format directly in the ioctl, drop v4l2_ext_format,
>>>> making V4L2_BUF_TYPE_VIDEO_[OUTPUT,CAPTURE] the only valid types.
>>>> - Drop VIDIOC_EXT_EXPBUF, since the only difference from VIDIOC_EXPBUF
>>>> was that with VIDIOC_EXT_EXPBUF we could export multiple planes at once.
>>>> I think we can add this later, so I removed it from this RFC to simplify it.
>>>> - Remove num_planes field from struct v4l2_ext_buffer
>>>> - Add flags field to struct v4l2_ext_create_buffers
>>>> - Reformulate struct v4l2_ext_plane
>>>> - Fix some bugs caught by v4l2-compliance
>>>> - Rebased on top of media/master (post 5.8-rc1)
>>>>
>>>> Changes in v3:
>>>> - Rebased on top of media/master (post 5.4-rc1)
>>>>
>>>> Changes in v2:
>>>> - Add reserved space to v4l2_ext_buffer so that new fields can be added
>>>> later on
>>>> ---
>>>> drivers/media/v4l2-core/v4l2-dev.c | 29 ++-
>>>> drivers/media/v4l2-core/v4l2-ioctl.c | 349 +++++++++++++++++++++++++--
>>>> include/media/v4l2-ioctl.h | 26 ++
>>>> include/uapi/linux/videodev2.h | 89 +++++++
>>>> 4 files changed, 471 insertions(+), 22 deletions(-)
>>>>
>>>
>>> <cut>
>>>
>>>> +/**
>>>> + * struct v4l2_ext_plane - extended plane buffer info
>>>> + * @buffer_length: size of the entire buffer in bytes, should fit
>>>> + * @offset + @plane_length
>>>> + * @plane_length: size of the plane in bytes.
>>>> + * @userptr: when memory is V4L2_MEMORY_USERPTR, a userspace pointer pointing
>>>> + * to this plane.
>>>> + * @dmabuf_fd: when memory is V4L2_MEMORY_DMABUF, a userspace file descriptor
>>>> + * associated with this plane.
>>>> + * @offset: offset in the memory buffer where the plane starts. If
>>>> + * V4L2_MEMORY_MMAP is used, then it can be a "cookie" that
>>>> + * should be passed to mmap() called on the video node.
>>>> + * @reserved: extra space reserved for future fields, must be set to 0.
>>>> + *
>>>> + *
>>>> + * Buffers consist of one or more planes, e.g. an YCbCr buffer with two planes
>>>> + * can have one plane for Y, and another for interleaved CbCr components.
>>>> + * Each plane can reside in a separate memory buffer, or even in
>>>> + * a completely separate memory node (e.g. in embedded devices).
>>>> + */
>>>> +struct v4l2_ext_plane {
>>>> + __u32 buffer_length;
>>>> + __u32 plane_length;
>>>> + union {
>>>> + __u64 userptr;
>>>> + __s32 dmabuf_fd;
>>>> + } m;
>>>> + __u32 offset;
>>>> + __u32 reserved[4];
>>>> +};
>>>> +
>>>> /**
>>>> * struct v4l2_buffer - video buffer info
>>>> * @index: id number of the buffer
>>>> @@ -1055,6 +1086,36 @@ struct v4l2_buffer {
>>>> };
>>>> };
>>>>
>>>> +/**
>>>> + * struct v4l2_ext_buffer - extended video buffer info
>>>> + * @index: id number of the buffer
>>>> + * @type: V4L2_BUF_TYPE_VIDEO_CAPTURE or V4L2_BUF_TYPE_VIDEO_OUTPUT
>>>> + * @flags: buffer informational flags
>>>> + * @field: enum v4l2_field; field order of the image in the buffer
>>>> + * @timestamp: frame timestamp
>>>> + * @sequence: sequence count of this frame
>>>> + * @memory: enum v4l2_memory; the method, in which the actual video data is
>>>> + * passed
>>>> + * @planes: per-plane buffer information
>>>> + * @request_fd: fd of the request that this buffer should use
>>>> + * @reserved: extra space reserved for future fields, must be set to 0
>>>> + *
>>>> + * Contains data exchanged by application and driver using one of the Streaming
>>>> + * I/O methods.
>>>> + */
>>>> +struct v4l2_ext_buffer {
>>>> + __u32 index;
>>>> + __u32 type;
>>>> + __u32 flags;
>>>> + __u32 field;
>>>> + __u64 timestamp;
>>>> + __u32 sequence;
>>>> + __u32 memory;
>>>> + __u32 request_fd;
>>>
>>> This should be __s32, at least for consistency with dmabuf_fd?
>>
>> I see that in struct v4l2_buffer, we have __s32, I don't mind changing it
>> to keep the consistency, I just don't see where this value can be a negative
>> number.
>
> here
> https://elixir.bootlin.com/linux/v5.8-rc4/source/drivers/media/common/videobuf2/videobuf2-v4l2.c#L134
I saw that -1 is used to signal an invalid value, but I was just wondering when request_fd = 0 is valid.
>
>>
>>>
>>>> + struct v4l2_ext_plane planes[VIDEO_MAX_PLANES];
>>>> + __u32 reserved[4];
>>>
>>> I think we have to reserve more words here for future extensions.
>>>
>>> I'd like also to propose to add here __s32 metadata_fd. The idea behind
>>> this is to have a way to pass per-frame metadata dmabuf buffers for
>>> synchronous type of metadata where the metadata is coming at the same
>>> time with data buffers. What would be the format of the metadata buffer
>>> is TBD.
>>>
>>> One option for metadata buffer format could be:
>>>
>>> header {
>>> num_ctrls
>>> array_of_ctrls [0..N]
>>> ctrl_id
>>> ctrl_size
>>> ctrl_offset
>>> }
>>>
>>> data {
>>> cid0 //offset of cid0 in dmabuf buffer
>>> cid1
>>> cidN
>>> }
>>
>> Would it be better if, instead of adding a medatata_fd inside struct v4l2_ext_buffer,
>> we create a new ioctl that gets this structs for the controls and sync them using the
>> Request API ?
>
> no, this solution has performance drawbacks when the metadata is big,
> think of 64K.
Why? You could still use a dmabuf in this new ioctl, no?
Regards,
Helen
>
>>
>> I'd like to avoid too much metadata in the buffer object.
>>
>> Regards,
>> Helen
>>
>>>
>>> This will make easy to get concrete ctrl id without a need to parse the
>>> whole metadata buffer. Also using dmabuf we don't need to copy data
>>> between userspace <-> kernelspace (just cache syncs through
>>> begin/end_cpu_access).
>>>
>>> The open question is who will validate the metadata buffer when it comes
>>> from userspace. The obvious answer is v4l2-core but looking into DRM
>>> subsytem they give more freedom to the drivers, and just provide generic
>>> helpers which are not mandatory.
>>>
>>> I guess this will be a voice in the wilderness but I wanted to know your
>>> opinion.
>>>
>>>> +};
>>>> +
>>>> #ifndef __KERNEL__
>>>> /**
>>>> * v4l2_timeval_to_ns - Convert timeval to nanoseconds
>>>> @@ -2520,6 +2581,29 @@ struct v4l2_create_buffers {
>>>> __u32 reserved[6];
>>>> };
>>>>
>>>> +/**
>>>> + * struct v4l2_ext_create_buffers - VIDIOC_EXT_CREATE_BUFS argument
>>>> + * @index: on return, index of the first created buffer
>>>> + * @count: entry: number of requested buffers,
>>>> + * return: number of created buffers
>>>> + * @memory: enum v4l2_memory; buffer memory type
>>>> + * @capabilities: capabilities of this buffer type.
>>>> + * @format: frame format, for which buffers are requested
>>>> + * @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).
>>>> + * @reserved: extra space reserved for future fields, must be set to 0
>>>> + */
>>>> +struct v4l2_ext_create_buffers {
>>>> + __u32 index;
>>>> + __u32 count;
>>>> + __u32 memory;
>>>> + struct v4l2_ext_pix_format format;
>>>> + __u32 capabilities;
>>>> + __u32 flags;
>>>> + __u32 reserved[4];
>>>> +};
>>>> +
>>>> /*
>>>> * 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
>>>> *
>>>> @@ -2623,6 +2707,11 @@ struct v4l2_create_buffers {
>>>> #define VIDIOC_G_EXT_PIX_FMT _IOWR('V', 104, struct v4l2_ext_pix_format)
>>>> #define VIDIOC_S_EXT_PIX_FMT _IOWR('V', 105, struct v4l2_ext_pix_format)
>>>> #define VIDIOC_TRY_EXT_PIX_FMT _IOWR('V', 106, struct v4l2_ext_pix_format)
>>>> +#define VIDIOC_EXT_CREATE_BUFS _IOWR('V', 107, struct v4l2_ext_create_buffers)
>>>> +#define VIDIOC_EXT_QUERYBUF _IOWR('V', 108, struct v4l2_ext_buffer)
>>>> +#define VIDIOC_EXT_QBUF _IOWR('V', 109, struct v4l2_ext_buffer)
>>>> +#define VIDIOC_EXT_DQBUF _IOWR('V', 110, struct v4l2_ext_buffer)
>>>> +#define VIDIOC_EXT_PREPARE_BUF _IOWR('V', 111, struct v4l2_ext_buffer)
>>>>
>>>> /* Reminder: when adding new ioctls please add support for them to
>>>> drivers/media/v4l2-core/v4l2-compat-ioctl32.c as well! */
>>>>
>>>
>
