v4l2_buffers.c

/*
 * V4L2 buffer helper functions.
 *
 * Copyright (C) 2017 Alexis Ballier <aballier@gentoo.org>
 * Copyright (C) 2017 Jorge Ramirez <jorge.ramirez-ortiz@linaro.org>
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <drm_fourcc.h>
#include <linux/videodev2.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <unistd.h>
#include <fcntl.h>
#include <poll.h>
#include "libavcodec/avcodec.h"
#include "libavcodec/internal.h"
#include "libavutil/hwcontext.h"
#include "v4l2_context.h"
#include "v4l2_buffers.h"
#include "v4l2_m2m.h"

#define USEC_PER_SEC 1000000

static inline V4L2m2mContext *buf_to_m2mctx(V4L2Buffer *buf)
{
    return V4L2_TYPE_IS_OUTPUT(buf->context->type) ?
        container_of(buf->context, V4L2m2mContext, output) :
        container_of(buf->context, V4L2m2mContext, capture);
}

static inline AVCodecContext *logger(V4L2Buffer *buf)
{
    return buf_to_m2mctx(buf)->avctx;
}

static inline void v4l2_set_pts(V4L2Buffer *out, int64_t pts)
{
    V4L2m2mContext *s = buf_to_m2mctx(out);
    AVRational v4l2_timebase = { 1, USEC_PER_SEC };
    int64_t v4l2_pts;

    if (pts == AV_NOPTS_VALUE)
        pts = 0;

    /* convert pts to v4l2 timebase */
    v4l2_pts = av_rescale_q(pts, s->avctx->time_base, v4l2_timebase);
    out->buf.timestamp.tv_usec = v4l2_pts % USEC_PER_SEC;
    out->buf.timestamp.tv_sec = v4l2_pts / USEC_PER_SEC;
}

static inline uint64_t v4l2_get_pts(V4L2Buffer *avbuf)
{
    V4L2m2mContext *s = buf_to_m2mctx(avbuf);
    AVRational v4l2_timebase = { 1, USEC_PER_SEC };
    int64_t v4l2_pts;

    /* convert pts back to encoder timebase */
    v4l2_pts = (int64_t)avbuf->buf.timestamp.tv_sec * USEC_PER_SEC +
                        avbuf->buf.timestamp.tv_usec;

    return av_rescale_q(v4l2_pts, v4l2_timebase, s->avctx->time_base);
}

static enum AVColorPrimaries v4l2_get_color_primaries(V4L2Buffer *buf)
{
    enum v4l2_ycbcr_encoding ycbcr;
    enum v4l2_colorspace cs;

    cs = V4L2_TYPE_IS_MULTIPLANAR(buf->buf.type) ?
        buf->context->format.fmt.pix_mp.colorspace :
        buf->context->format.fmt.pix.colorspace;

    ycbcr = V4L2_TYPE_IS_MULTIPLANAR(buf->buf.type) ?
        buf->context->format.fmt.pix_mp.ycbcr_enc:
        buf->context->format.fmt.pix.ycbcr_enc;

    switch(ycbcr) {
    case V4L2_YCBCR_ENC_XV709:
    case V4L2_YCBCR_ENC_709: return AVCOL_PRI_BT709;
    case V4L2_YCBCR_ENC_XV601:
    case V4L2_YCBCR_ENC_601:return AVCOL_PRI_BT470M;
    default:
        break;
    }

    switch(cs) {
    case V4L2_COLORSPACE_470_SYSTEM_BG: return AVCOL_PRI_BT470BG;
    case V4L2_COLORSPACE_SMPTE170M: return AVCOL_PRI_SMPTE170M;
    case V4L2_COLORSPACE_SMPTE240M: return AVCOL_PRI_SMPTE240M;
    case V4L2_COLORSPACE_BT2020: return AVCOL_PRI_BT2020;
    default:
        break;
    }

    return AVCOL_PRI_UNSPECIFIED;
}

static enum AVColorRange v4l2_get_color_range(V4L2Buffer *buf)
{
    enum v4l2_quantization qt;

    qt = V4L2_TYPE_IS_MULTIPLANAR(buf->buf.type) ?
        buf->context->format.fmt.pix_mp.quantization :
        buf->context->format.fmt.pix.quantization;

    switch (qt) {
    case V4L2_QUANTIZATION_LIM_RANGE: return AVCOL_RANGE_MPEG;
    case V4L2_QUANTIZATION_FULL_RANGE: return AVCOL_RANGE_JPEG;
    default:
        break;
    }

     return AVCOL_RANGE_UNSPECIFIED;
}

static enum AVColorSpace v4l2_get_color_space(V4L2Buffer *buf)
{
    enum v4l2_ycbcr_encoding ycbcr;
    enum v4l2_colorspace cs;

    cs = V4L2_TYPE_IS_MULTIPLANAR(buf->buf.type) ?
        buf->context->format.fmt.pix_mp.colorspace :
        buf->context->format.fmt.pix.colorspace;

    ycbcr = V4L2_TYPE_IS_MULTIPLANAR(buf->buf.type) ?
        buf->context->format.fmt.pix_mp.ycbcr_enc:
        buf->context->format.fmt.pix.ycbcr_enc;

    switch(cs) {
    case V4L2_COLORSPACE_SRGB: return AVCOL_SPC_RGB;
    case V4L2_COLORSPACE_REC709: return AVCOL_SPC_BT709;
    case V4L2_COLORSPACE_470_SYSTEM_M: return AVCOL_SPC_FCC;
    case V4L2_COLORSPACE_470_SYSTEM_BG: return AVCOL_SPC_BT470BG;
    case V4L2_COLORSPACE_SMPTE170M: return AVCOL_SPC_SMPTE170M;
    case V4L2_COLORSPACE_SMPTE240M: return AVCOL_SPC_SMPTE240M;
    case V4L2_COLORSPACE_BT2020:
        if (ycbcr == V4L2_YCBCR_ENC_BT2020_CONST_LUM)
            return AVCOL_SPC_BT2020_CL;
        else
             return AVCOL_SPC_BT2020_NCL;
    default:
        break;
    }

    return AVCOL_SPC_UNSPECIFIED;
}

static enum AVColorTransferCharacteristic v4l2_get_color_trc(V4L2Buffer *buf)
{
    enum v4l2_ycbcr_encoding ycbcr;
    enum v4l2_xfer_func xfer;
    enum v4l2_colorspace cs;

    cs = V4L2_TYPE_IS_MULTIPLANAR(buf->buf.type) ?
        buf->context->format.fmt.pix_mp.colorspace :
        buf->context->format.fmt.pix.colorspace;

    ycbcr = V4L2_TYPE_IS_MULTIPLANAR(buf->buf.type) ?
        buf->context->format.fmt.pix_mp.ycbcr_enc:
        buf->context->format.fmt.pix.ycbcr_enc;

    xfer = V4L2_TYPE_IS_MULTIPLANAR(buf->buf.type) ?
        buf->context->format.fmt.pix_mp.xfer_func:
        buf->context->format.fmt.pix.xfer_func;

    switch (xfer) {
    case V4L2_XFER_FUNC_709: return AVCOL_TRC_BT709;
    case V4L2_XFER_FUNC_SRGB: return AVCOL_TRC_IEC61966_2_1;
    default:
        break;
    }

    switch (cs) {
    case V4L2_COLORSPACE_470_SYSTEM_M: return AVCOL_TRC_GAMMA22;
    case V4L2_COLORSPACE_470_SYSTEM_BG: return AVCOL_TRC_GAMMA28;
    case V4L2_COLORSPACE_SMPTE170M: return AVCOL_TRC_SMPTE170M;
    case V4L2_COLORSPACE_SMPTE240M: return AVCOL_TRC_SMPTE240M;
    default:
        break;
    }

    switch (ycbcr) {
    case V4L2_YCBCR_ENC_XV709:
    case V4L2_YCBCR_ENC_XV601: return AVCOL_TRC_BT1361_ECG;
    default:
        break;
    }

    return AVCOL_TRC_UNSPECIFIED;
}

static uint8_t * v4l2_get_drm_frame(V4L2Buffer *avbuf)
{
    AVDRMFrameDescriptor *drm_desc = &avbuf->drm_frame;
    AVDRMLayerDescriptor *layer;

    /* fill the DRM frame descriptor */
    drm_desc->nb_objects = avbuf->num_planes;
    drm_desc->nb_layers = 1;

    layer = &drm_desc->layers[0];
    layer->nb_planes = avbuf->num_planes;

    for (int i = 0; i < avbuf->num_planes; i++) {
        layer->planes[i].object_index = i;
        layer->planes[i].offset = 0;
        layer->planes[i].pitch = avbuf->plane_info[i].bytesperline;
    }

    switch (avbuf->context->av_pix_fmt) {
    case AV_PIX_FMT_YUYV422:

        layer->format = DRM_FORMAT_YUYV;
        layer->nb_planes = 1;

        break;

    case AV_PIX_FMT_NV12:
    case AV_PIX_FMT_NV21:

        layer->format = avbuf->context->av_pix_fmt == AV_PIX_FMT_NV12 ?
            DRM_FORMAT_NV12 : DRM_FORMAT_NV21;

        if (avbuf->num_planes > 1)
            break;

        layer->nb_planes = 2;

        layer->planes[1].object_index = 0;
        layer->planes[1].offset = avbuf->plane_info[0].bytesperline *
            avbuf->context->format.fmt.pix.height;
        layer->planes[1].pitch = avbuf->plane_info[0].bytesperline;
        break;

    case AV_PIX_FMT_YUV420P:

        layer->format = DRM_FORMAT_YUV420;

        if (avbuf->num_planes > 1)
            break;

        layer->nb_planes = 3;

        layer->planes[1].object_index = 0;
        layer->planes[1].offset = avbuf->plane_info[0].bytesperline *
            avbuf->context->format.fmt.pix.height;
        layer->planes[1].pitch = avbuf->plane_info[0].bytesperline >> 1;

        layer->planes[2].object_index = 0;
        layer->planes[2].offset = layer->planes[1].offset +
            ((avbuf->plane_info[0].bytesperline *
              avbuf->context->format.fmt.pix.height) >> 2);
        layer->planes[2].pitch = avbuf->plane_info[0].bytesperline >> 1;
        break;

    default:
        drm_desc->nb_layers = 0;
        break;
    }

    return (uint8_t *) drm_desc;
}

static void v4l2_free_buffer(void *opaque, uint8_t *data)
{
    V4L2Buffer* avbuf = opaque;
    V4L2m2mContext *s = buf_to_m2mctx(avbuf);

    if (atomic_fetch_sub(&avbuf->context_refcount, 1) == 1) {
        atomic_fetch_sub_explicit(&s->refcount, 1, memory_order_acq_rel);

        if (s->reinit) {
            if (!atomic_load(&s->refcount))
                sem_post(&s->refsync);
        } else {
            if (s->draining) {
                /* no need to queue more buffers to the driver */
                avbuf->status = V4L2BUF_AVAILABLE;
            }
            else if (avbuf->context->streamon)
                ff_v4l2_buffer_enqueue(avbuf);
        }

        av_buffer_unref(&avbuf->context_ref);
    }
}

static int v4l2_buffer_export_drm(V4L2Buffer* avbuf)
{
    struct v4l2_exportbuffer expbuf;
    int i, ret;

    for (i = 0; i < avbuf->num_planes; i++) {
        memset(&expbuf, 0, sizeof(expbuf));

        expbuf.index = avbuf->buf.index;
        expbuf.type = avbuf->buf.type;
        expbuf.plane = i;

        ret = ioctl(buf_to_m2mctx(avbuf)->fd, VIDIOC_EXPBUF, &expbuf);
        if (ret < 0)
            return AVERROR(errno);

        if (V4L2_TYPE_IS_MULTIPLANAR(avbuf->buf.type)) {
            /* drm frame */
            avbuf->drm_frame.objects[i].size = avbuf->buf.m.planes[i].length;
            avbuf->drm_frame.objects[i].fd = expbuf.fd;
            avbuf->drm_frame.objects[i].format_modifier = DRM_FORMAT_MOD_LINEAR;
        } else {
            /* drm frame */
            avbuf->drm_frame.objects[0].size = avbuf->buf.length;
            avbuf->drm_frame.objects[0].fd = expbuf.fd;
            avbuf->drm_frame.objects[0].format_modifier = DRM_FORMAT_MOD_LINEAR;
        }
    }

    return 0;
}

static int v4l2_buf_increase_ref(V4L2Buffer *in)
{
    V4L2m2mContext *s = buf_to_m2mctx(in);

    if (in->context_ref)
        atomic_fetch_add(&in->context_refcount, 1);
    else {
        in->context_ref = av_buffer_ref(s->self_ref);
        if (!in->context_ref)
            return AVERROR(ENOMEM);

        in->context_refcount = 1;
    }

    in->status = V4L2BUF_RET_USER;
    atomic_fetch_add_explicit(&s->refcount, 1, memory_order_relaxed);

    return 0;
}

static int v4l2_buf_to_bufref_drm(V4L2Buffer *in, AVBufferRef **buf)
{
    int ret;

    *buf = av_buffer_create((uint8_t *) &in->drm_frame,
                            sizeof(in->drm_frame),
                            v4l2_free_buffer,
                            in, AV_BUFFER_FLAG_READONLY);
    if (!*buf)
        return AVERROR(ENOMEM);

    ret = v4l2_buf_increase_ref(in);
    if (ret)
         av_buffer_unref(buf);

    return ret;
}

static int v4l2_buf_to_bufref(V4L2Buffer *in, int plane, AVBufferRef **buf)
{
    int ret;

    if (plane >= in->num_planes)
        return AVERROR(EINVAL);

    /* most encoders return 0 in data_offset but vp8 does require this value */
    *buf = av_buffer_create((char *)in->plane_info[plane].mm_addr + in->planes[plane].data_offset,
                            in->plane_info[plane].length,
                            v4l2_free_buffer,
                            in, 0);
    if (!*buf)
        return AVERROR(ENOMEM);

    ret = v4l2_buf_increase_ref(in);
    if (ret)
        av_buffer_unref(buf);

    return ret;
}

static int v4l2_bufref_to_buf(V4L2Buffer *out, int plane, const uint8_t* data, int size, AVBufferRef* bref)
{
    unsigned int bytesused, length;

    if (plane >= out->num_planes)
        return AVERROR(EINVAL);

    bytesused = FFMIN(size, out->plane_info[plane].length);
    length = out->plane_info[plane].length;

    memcpy(out->plane_info[plane].mm_addr, data,
           FFMIN(size, out->plane_info[plane].length));

    if (V4L2_TYPE_IS_MULTIPLANAR(out->buf.type)) {
        out->planes[plane].bytesused = bytesused;
        out->planes[plane].length = length;
    } else {
        out->buf.bytesused = bytesused;
        out->buf.length = length;
    }

    return 0;
}

/******************************************************************************
 *
 *              V4L2uffer interface
 *
 ******************************************************************************/

int ff_v4l2_buffer_avframe_to_buf(const AVFrame *frame, V4L2Buffer* out)
{
    int i, ret;

    for(i = 0; i < out->num_planes; i++) {
        ret = v4l2_bufref_to_buf(out, i,
                                frame->buf[i]->data,
                                frame->buf[i]->size,
                                frame->buf[i]);
        if (ret)
            return ret;
    }

    v4l2_set_pts(out, frame->pts);

    return 0;
}

int ff_v4l2_buffer_buf_to_avframe(AVFrame *frame, V4L2Buffer *avbuf)
{
    V4L2m2mContext *s = buf_to_m2mctx(avbuf);
    int i, ret;

    av_frame_unref(frame);

    /* 1. get references to the actual data */
    if (buf_to_m2mctx(avbuf)->output_drm) {
        /* 1. get references to the actual data */
        ret = v4l2_buf_to_bufref_drm(avbuf, &frame->buf[0]);
        if (ret)
            return ret;

        frame->data[0] = (uint8_t *) v4l2_get_drm_frame(avbuf);
        frame->format = AV_PIX_FMT_DRM_PRIME;
        frame->hw_frames_ctx = av_buffer_ref(avbuf->context->frames_ref);
    } else {
        /* 1. get references to the actual data */
        for (i = 0; i < avbuf->num_planes; i++) {
            ret = v4l2_buf_to_bufref(avbuf, i, &frame->buf[i]);
            if (ret)
                return ret;

            frame->linesize[i] = avbuf->plane_info[i].bytesperline;
            frame->data[i] = frame->buf[i]->data;
        }

        /* 1.1 fixup special cases */
        switch (avbuf->context->av_pix_fmt) {
        case AV_PIX_FMT_NV12:
            if (avbuf->num_planes > 1)
                break;
            frame->linesize[1] = avbuf->plane_info[0].bytesperline;
            frame->data[1] = frame->buf[0]->data + avbuf->plane_info[0].bytesperline * avbuf->context->format.fmt.pix_mp.height;
            break;
        case AV_PIX_FMT_YUV420P:
            if (avbuf->num_planes > 1)
                break;
            frame->linesize[1] = frame->linesize[2] = avbuf->plane_info[0].bytesperline >> 1;
            frame->data[1] = frame->buf[0]->data + avbuf->plane_info[0].bytesperline * avbuf->context->format.fmt.pix_mp.height;
            frame->data[2] = frame->data[1] + ((avbuf->plane_info[0].bytesperline * avbuf->context->format.fmt.pix_mp.height) >> 2);
            break;
        default:
            break;
        }
        frame->format = avbuf->context->av_pix_fmt;
    }

    /* 2. get frame information */
    frame->key_frame = !!(avbuf->buf.flags & V4L2_BUF_FLAG_KEYFRAME);
    frame->color_primaries = v4l2_get_color_primaries(avbuf);
    frame->color_range = v4l2_get_color_range(avbuf);
    frame->colorspace = v4l2_get_color_space(avbuf);
    frame->color_trc = v4l2_get_color_trc(avbuf);
    frame->pts = v4l2_get_pts(avbuf);

    /* these two values are updated also during re-init in v4l2_process_driver_event */
    frame->height = s->output.height;
    frame->width = s->output.width;

    /* 3. report errors upstream */
    if (avbuf->buf.flags & V4L2_BUF_FLAG_ERROR) {
        av_log(logger(avbuf), AV_LOG_ERROR, "%s: driver decode error\n", avbuf->context->name);
        frame->decode_error_flags |= FF_DECODE_ERROR_INVALID_BITSTREAM;
    }

    return 0;
}

int ff_v4l2_buffer_buf_to_avpkt(AVPacket *pkt, V4L2Buffer *avbuf)
{
    int ret;

    av_packet_unref(pkt);
    ret = v4l2_buf_to_bufref(avbuf, 0, &pkt->buf);
    if (ret)
        return ret;

    pkt->size = V4L2_TYPE_IS_MULTIPLANAR(avbuf->buf.type) ?
        avbuf->buf.m.planes[0].bytesused : avbuf->buf.bytesused;
    pkt->data = pkt->buf->data;

    if (avbuf->buf.flags & V4L2_BUF_FLAG_KEYFRAME)
        pkt->flags |= AV_PKT_FLAG_KEY;

    if (avbuf->buf.flags & V4L2_BUF_FLAG_ERROR) {
        av_log(logger(avbuf), AV_LOG_ERROR, "%s driver encode error\n", avbuf->context->name);
        pkt->flags |= AV_PKT_FLAG_CORRUPT;
    }

    pkt->dts = pkt->pts = v4l2_get_pts(avbuf);

    return 0;
}

int ff_v4l2_buffer_avpkt_to_buf(const AVPacket *pkt, V4L2Buffer *out)
{
    int ret;

    ret = v4l2_bufref_to_buf(out, 0, pkt->data, pkt->size, pkt->buf);
    if (ret)
        return ret;

    v4l2_set_pts(out, pkt->pts);

    if (pkt->flags & AV_PKT_FLAG_KEY)
        out->flags = V4L2_BUF_FLAG_KEYFRAME;

    return 0;
}

int ff_v4l2_buffer_initialize(V4L2Buffer* avbuf, int index)
{
    V4L2Context *ctx = avbuf->context;
    int ret, i;

    avbuf->buf.memory = V4L2_MEMORY_MMAP;
    avbuf->buf.type = ctx->type;
    avbuf->buf.index = index;

    if (buf_to_m2mctx(avbuf)->output_drm) {
        AVHWFramesContext *hwframes;

        av_buffer_unref(&ctx->frames_ref);

        ctx->frames_ref = av_hwframe_ctx_alloc(buf_to_m2mctx(avbuf)->device_ref);
        if (!ctx->frames_ref) {
            ret = AVERROR(ENOMEM);
            return ret;
        }

        hwframes = (AVHWFramesContext*)ctx->frames_ref->data;
        hwframes->format = AV_PIX_FMT_DRM_PRIME;
        hwframes->sw_format = ctx->av_pix_fmt;
        hwframes->width = ctx->width;
        hwframes->height = ctx->height;
        ret = av_hwframe_ctx_init(ctx->frames_ref);
        if (ret < 0)
            return ret;
    }

    if (V4L2_TYPE_IS_MULTIPLANAR(ctx->type)) {
        avbuf->buf.length = VIDEO_MAX_PLANES;
        avbuf->buf.m.planes = avbuf->planes;
    }

    ret = ioctl(buf_to_m2mctx(avbuf)->fd, VIDIOC_QUERYBUF, &avbuf->buf);
    if (ret < 0)
        return AVERROR(errno);

    if (V4L2_TYPE_IS_MULTIPLANAR(ctx->type)) {
        avbuf->num_planes = 0;
        for (;;) {
            /* in MP, the V4L2 API states that buf.length means num_planes */
            if (avbuf->num_planes >= avbuf->buf.length)
                break;

            if (avbuf->buf.m.planes[avbuf->num_planes].length)
                avbuf->num_planes++;
        }
    } else
        avbuf->num_planes = 1;

    for (i = 0; i < avbuf->num_planes; i++) {

        avbuf->plane_info[i].bytesperline = V4L2_TYPE_IS_MULTIPLANAR(ctx->type) ?
            ctx->format.fmt.pix_mp.plane_fmt[i].bytesperline :
            ctx->format.fmt.pix.bytesperline;

        if (V4L2_TYPE_IS_MULTIPLANAR(ctx->type)) {
            avbuf->plane_info[i].length = avbuf->buf.m.planes[i].length;

            if ((V4L2_TYPE_IS_OUTPUT(ctx->type) && buf_to_m2mctx(avbuf)->output_drm) ||
                !buf_to_m2mctx(avbuf)->output_drm) {
                avbuf->plane_info[i].mm_addr = mmap(NULL, avbuf->buf.m.planes[i].length,
                                               PROT_READ | PROT_WRITE, MAP_SHARED,
                                               buf_to_m2mctx(avbuf)->fd,
                                               avbuf->buf.m.planes[i].m.mem_offset);
            }
        } else {
            avbuf->plane_info[i].length = avbuf->buf.length;

            if ((V4L2_TYPE_IS_OUTPUT(ctx->type) && buf_to_m2mctx(avbuf)->output_drm) ||
                !buf_to_m2mctx(avbuf)->output_drm) {
                avbuf->plane_info[i].mm_addr = mmap(NULL, avbuf->buf.length,
                                              PROT_READ | PROT_WRITE, MAP_SHARED,
                                              buf_to_m2mctx(avbuf)->fd,
                                              avbuf->buf.m.offset);
            }
        }

        if (avbuf->plane_info[i].mm_addr == MAP_FAILED)
            return AVERROR(ENOMEM);
    }

    avbuf->status = V4L2BUF_AVAILABLE;

    if (V4L2_TYPE_IS_MULTIPLANAR(ctx->type)) {
        avbuf->buf.length   = avbuf->num_planes;
        avbuf->buf.m.planes = avbuf->planes;
    } else {
        avbuf->buf.bytesused = avbuf->planes[0].bytesused;
        avbuf->buf.length    = avbuf->planes[0].length;
    }

    if (V4L2_TYPE_IS_OUTPUT(ctx->type))
        return 0;

    if (buf_to_m2mctx(avbuf)->output_drm) {
        ret = v4l2_buffer_export_drm(avbuf);
        if (ret)
                return ret;
    }

    return ff_v4l2_buffer_enqueue(avbuf);
}

int ff_v4l2_buffer_enqueue(V4L2Buffer* avbuf)
{
    int ret;

    avbuf->buf.flags = avbuf->flags;

    ret = ioctl(buf_to_m2mctx(avbuf)->fd, VIDIOC_QBUF, &avbuf->buf);
    if (ret < 0)
        return AVERROR(errno);

    avbuf->status = V4L2BUF_IN_DRIVER;

    return 0;
}