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Message-ID: <3d7275bc1c0ae871010db34927681d648c1676e0.camel@ndufresne.ca>
Subject: Re: [PATCH v3 05/15] media: mtk-vcodec: vdec: support stateless API
From:   Nicolas Dufresne <nicolas@ndufresne.ca>
To:     Alexandre Courbot <acourbot@chromium.org>,
        Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
Cc:     Tiffany Lin <tiffany.lin@mediatek.com>,
        Andrew-CT Chen <andrew-ct.chen@mediatek.com>,
        Rob Herring <robh+dt@kernel.org>,
        Yunfei Dong <yunfei.dong@mediatek.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Hans Verkuil <hverkuil-cisco@xs4all.nl>,
        linux-media <linux-media@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@lists.infradead.org>
Date:   Mon, 15 Mar 2021 11:16:26 -0400
In-Reply-To: <CAPBb6MWtPuBNLpMK6U1-rfvTcPRnOEjJ06zTawxyD+pMSJ=uGQ@mail.gmail.com>
References: <20210226100148.1663389-1-acourbot@chromium.org>
         <20210226100148.1663389-6-acourbot@chromium.org>
         <CAAEAJfDyHYGf+J6WDHchVATOvj5AJpO8dkAStiNGNobJ9Uz8Yw@mail.gmail.com>
         <CAPBb6MWtPuBNLpMK6U1-rfvTcPRnOEjJ06zTawxyD+pMSJ=uGQ@mail.gmail.com>
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Le lundi 15 mars 2021 à 20:28 +0900, Alexandre Courbot a écrit :
> Hi Ezequiel, thanks for the feedback!
> 
> On Thu, Mar 4, 2021 at 6:30 AM Ezequiel Garcia
> <ezequiel@vanguardiasur.com.ar> wrote:
> > 
> > Hello Alex,
> > 
> > Thanks for the patch.
> > 
> > On Fri, 26 Feb 2021 at 07:06, Alexandre Courbot <acourbot@chromium.org>
> > wrote:
> > > 
> > > From: Yunfei Dong <yunfei.dong@mediatek.com>
> > > 
> > > Support the stateless codec API that will be used by MT8183.
> > > 
> > > Signed-off-by: Yunfei Dong <yunfei.dong@mediatek.com>
> > > [acourbot: refactor, cleanup and split]
> > > Co-developed-by: Alexandre Courbot <acourbot@chromium.org>
> > > Signed-off-by: Alexandre Courbot <acourbot@chromium.org>
> > > ---
> > >  drivers/media/platform/mtk-vcodec/Makefile    |   1 +
> > >  .../platform/mtk-vcodec/mtk_vcodec_dec.c      |  66 ++-
> > >  .../platform/mtk-vcodec/mtk_vcodec_dec.h      |   9 +-
> > >  .../mtk-vcodec/mtk_vcodec_dec_stateless.c     | 427 ++++++++++++++++++
> > >  .../platform/mtk-vcodec/mtk_vcodec_drv.h      |   3 +
> > >  5 files changed, 503 insertions(+), 3 deletions(-)
> > >  create mode 100644 drivers/media/platform/mtk-
> > > vcodec/mtk_vcodec_dec_stateless.c
> > > 
> > [..]
> > 
> > > +
> > > +static const struct mtk_stateless_control mtk_stateless_controls[] = {
> > > +       {
> > > +               .cfg = {
> > > +                       .id = V4L2_CID_STATELESS_H264_SPS,
> > > +               },
> > > +               .codec_type = V4L2_PIX_FMT_H264_SLICE,
> > > +               .needed_in_request = true,
> > 
> > This "needed_in_request" is not really required, as controls
> > are not volatile, and their value is stored per-context (per-fd).
> > 
> > It's perfectly valid for an application to pass the SPS control
> > at the beginning of the sequence, and then omit it
> > in further requests.
> 
> If I understand how v4l2_ctrl_request_hdl_ctrl_find() works with
> requests, this boolean only checks that the control has been provided
> at least once, and not that it is provided with every request. Without
> it we could send a frame to the firmware without e.g. setting an SPS,
> which would be a problem.

In other drivers (Cedrus and RKVDEC) this was actually checking if the control
was part of the request, I doubt the framework have a state for "being set
once", as control have no set/unset state. Did you wrote this code and tested
this intended behaviour or borred that code from somewhere else ?

> 
> > 
> > > +       },
> > > +       {
> > > +               .cfg = {
> > > +                       .id = V4L2_CID_STATELESS_H264_PPS,
> > > +               },
> > > +               .codec_type = V4L2_PIX_FMT_H264_SLICE,
> > > +               .needed_in_request = true,
> > > +       },
> > > +       {
> > > +               .cfg = {
> > > +                       .id = V4L2_CID_STATELESS_H264_SCALING_MATRIX,
> > > +               },
> > > +               .codec_type = V4L2_PIX_FMT_H264_SLICE,
> > > +               .needed_in_request = true,
> > > +       },
> > > +       {
> > > +               .cfg = {
> > > +                       .id = V4L2_CID_STATELESS_H264_DECODE_PARAMS,
> > > +               },
> > > +               .codec_type = V4L2_PIX_FMT_H264_SLICE,
> > > +               .needed_in_request = true,
> > > +       },
> > > +       {
> > > +               .cfg = {
> > > +                       .id = V4L2_CID_MPEG_VIDEO_H264_PROFILE,
> > > +                       .def = V4L2_MPEG_VIDEO_H264_PROFILE_MAIN,
> > > +                       .max = V4L2_MPEG_VIDEO_H264_PROFILE_HIGH,
> > > +                       .menu_skip_mask =
> > > +                               BIT(V4L2_MPEG_VIDEO_H264_PROFILE_BASELINE)
> > > |
> > > +                              
> > > BIT(V4L2_MPEG_VIDEO_H264_PROFILE_EXTENDED),
> > > +               },
> > > +               .codec_type = V4L2_PIX_FMT_H264_SLICE,
> > > +       },
> > > +       {
> > > +               .cfg = {
> > > +                       .id = V4L2_CID_STATELESS_H264_DECODE_MODE,
> > > +                       .min =
> > > V4L2_STATELESS_H264_DECODE_MODE_FRAME_BASED,
> > > +                       .def =
> > > V4L2_STATELESS_H264_DECODE_MODE_FRAME_BASED,
> > > +                       .max =
> > > V4L2_STATELESS_H264_DECODE_MODE_FRAME_BASED,
> > > +               },
> > > +               .codec_type = V4L2_PIX_FMT_H264_SLICE,
> > > +       },
> > > +};
> > 
> > Applications also need to know which V4L2_CID_STATELESS_H264_START_CODE
> > the driver supports. From a next patch, this case seems to be
> > V4L2_STATELESS_H264_START_CODE_ANNEX_B.
> 
> Indeed - I've added the control, thanks for catching this!
> 
> > 
> > > +#define NUM_CTRLS ARRAY_SIZE(mtk_stateless_controls)
> > > +
> > > +static const struct mtk_video_fmt mtk_video_formats[] = {
> > > +       {
> > > +               .fourcc = V4L2_PIX_FMT_H264_SLICE,
> > > +               .type = MTK_FMT_DEC,
> > > +               .num_planes = 1,
> > > +       },
> > > +       {
> > > +               .fourcc = V4L2_PIX_FMT_MM21,
> > > +               .type = MTK_FMT_FRAME,
> > > +               .num_planes = 2,
> > > +       },
> > > +};
> > > +#define NUM_FORMATS ARRAY_SIZE(mtk_video_formats)
> > > +#define DEFAULT_OUT_FMT_IDX    0
> > > +#define DEFAULT_CAP_FMT_IDX    1
> > > +
> > > +static const struct mtk_codec_framesizes mtk_vdec_framesizes[] = {
> > > +       {
> > > +               .fourcc = V4L2_PIX_FMT_H264_SLICE,
> > > +               .stepwise = {
> > > +                       MTK_VDEC_MIN_W, MTK_VDEC_MAX_W, 16,
> > > +                       MTK_VDEC_MIN_H, MTK_VDEC_MAX_H, 16,
> > > +               },
> > > +       },
> > > +};
> > > +
> > > +#define NUM_SUPPORTED_FRAMESIZE ARRAY_SIZE(mtk_vdec_framesizes)
> > > +
> > > +static void mtk_vdec_stateless_set_dst_payload(struct mtk_vcodec_ctx
> > > *ctx,
> > > +                                              struct vdec_fb *fb)
> > > +{
> > > +       struct mtk_video_dec_buf *vdec_frame_buf =
> > > +               container_of(fb, struct mtk_video_dec_buf, frame_buffer);
> > > +       struct vb2_v4l2_buffer *vb = &vdec_frame_buf->m2m_buf.vb;
> > > +       unsigned int cap_y_size = ctx-
> > > >q_data[MTK_Q_DATA_DST].sizeimage[0];
> > > +
> > > +       vb2_set_plane_payload(&vb->vb2_buf, 0, cap_y_size);
> > > +       if (ctx->q_data[MTK_Q_DATA_DST].fmt->num_planes == 2) {
> > > +               unsigned int cap_c_size =
> > > +                       ctx->q_data[MTK_Q_DATA_DST].sizeimage[1];
> > > +
> > > +               vb2_set_plane_payload(&vb->vb2_buf, 1, cap_c_size);
> > > +       }
> > > +}
> > > +
> > > +static struct vdec_fb *vdec_get_cap_buffer(struct mtk_vcodec_ctx *ctx,
> > > +                                          struct vb2_v4l2_buffer
> > > *vb2_v4l2)
> > > +{
> > > +       struct mtk_video_dec_buf *framebuf =
> > > +               container_of(vb2_v4l2, struct mtk_video_dec_buf,
> > > m2m_buf.vb);
> > > +       struct vdec_fb *pfb = &framebuf->frame_buffer;
> > > +       struct vb2_buffer *dst_buf = &vb2_v4l2->vb2_buf;
> > > +
> > > +       pfb = &framebuf->frame_buffer;
> > > +       pfb->base_y.va = vb2_plane_vaddr(dst_buf, 0);
> > 
> > Are you sure you need a CPU mapping? It seems strange.
> > I'll comment some more on the next patch(es).
> 
> I'll answer on the next patch since this is where that mapping is being used.
> 
> > 
> > > +       pfb->base_y.dma_addr = vb2_dma_contig_plane_dma_addr(dst_buf, 0);
> > > +       pfb->base_y.size = ctx->q_data[MTK_Q_DATA_DST].sizeimage[0];
> > > +
> > > +       if (ctx->q_data[MTK_Q_DATA_DST].fmt->num_planes == 2) {
> > > +               pfb->base_c.va = vb2_plane_vaddr(dst_buf, 1);
> > > +               pfb->base_c.dma_addr =
> > > +                       vb2_dma_contig_plane_dma_addr(dst_buf, 1);
> > > +               pfb->base_c.size = ctx-
> > > >q_data[MTK_Q_DATA_DST].sizeimage[1];
> > > +       }
> > > +       mtk_v4l2_debug(1,
> > > +               "id=%d Framebuf  pfb=%p VA=%p Y_DMA=%pad C_DMA=%pad
> > > Size=%zx frame_count = %d",
> > > +               dst_buf->index, pfb,
> > > +               pfb->base_y.va, &pfb->base_y.dma_addr,
> > > +               &pfb->base_c.dma_addr, pfb->base_y.size,
> > > +               ctx->decoded_frame_cnt);
> > > +
> > > +       return pfb;
> > > +}
> > > +
> > > +static void vb2ops_vdec_buf_request_complete(struct vb2_buffer *vb)
> > > +{
> > > +       struct mtk_vcodec_ctx *ctx = vb2_get_drv_priv(vb->vb2_queue);
> > > +
> > > +       v4l2_ctrl_request_complete(vb->req_obj.req, &ctx->ctrl_hdl);
> > > +}
> > > +
> > > +static int fops_media_request_validate(struct media_request *mreq)
> > > +{
> > > +       const unsigned int buffer_cnt = vb2_request_buffer_cnt(mreq);
> > > +       struct mtk_vcodec_ctx *ctx = NULL;
> > > +       struct media_request_object *req_obj;
> > > +       struct v4l2_ctrl_handler *parent_hdl, *hdl;
> > > +       struct v4l2_ctrl *ctrl;
> > > +       unsigned int i;
> > > +
> > > +       switch (buffer_cnt) {
> > > +       case 1:
> > > +               /* We expect exactly one buffer with the request */
> > > +               break;
> > > +       case 0:
> > > +               mtk_v4l2_err("No buffer provided with the request");
> > > +               return -ENOENT;
> > > +       default:
> > > +               mtk_v4l2_err("Too many buffers (%d) provided with the
> > > request",
> > > +                            buffer_cnt);
> > > +               return -EINVAL;
> > > +       }
> > > +
> > > +       list_for_each_entry(req_obj, &mreq->objects, list) {
> > > +               struct vb2_buffer *vb;
> > > +
> > > +               if (vb2_request_object_is_buffer(req_obj)) {
> > > +                       vb = container_of(req_obj, struct vb2_buffer,
> > > req_obj);
> > > +                       ctx = vb2_get_drv_priv(vb->vb2_queue);
> > > +                       break;
> > > +               }
> > > +       }
> > > +
> > > +       if (!ctx) {
> > > +               mtk_v4l2_err("Cannot find buffer for request");
> > > +               return -ENOENT;
> > > +       }
> > > +
> > > +       parent_hdl = &ctx->ctrl_hdl;
> > > +
> > > +       hdl = v4l2_ctrl_request_hdl_find(mreq, parent_hdl);
> > > +       if (!hdl) {
> > > +               mtk_v4l2_err("Cannot find control handler for request\n");
> > > +               return -ENOENT;
> > > +       }
> > > +
> > > +       for (i = 0; i < NUM_CTRLS; i++) {
> > > +               if (mtk_stateless_controls[i].codec_type != ctx-
> > > >current_codec)
> > > +                       continue;
> > > +               if (!mtk_stateless_controls[i].needed_in_request)
> > > +                       continue;
> > > +
> > > +               ctrl = v4l2_ctrl_request_hdl_ctrl_find(hdl,
> > > +                                        
> > > mtk_stateless_controls[i].cfg.id);
> > > +               if (!ctrl) {
> > > +                       mtk_v4l2_err("Missing required codec control\n");
> > > +                       return -ENOENT;
> > > +               }
> > > +       }
> > > +
> > > +       v4l2_ctrl_request_hdl_put(hdl);
> > > +
> > > +       return vb2_request_validate(mreq);
> > > +}
> > > +
> > > +static void mtk_vdec_worker(struct work_struct *work)
> > > +{
> > > +       struct mtk_vcodec_ctx *ctx =
> > > +               container_of(work, struct mtk_vcodec_ctx, decode_work);
> > > +       struct mtk_vcodec_dev *dev = ctx->dev;
> > > +       struct vb2_v4l2_buffer *vb2_v4l2_src, *vb2_v4l2_dst;
> > > +       struct vb2_buffer *vb2_src;
> > > +       struct mtk_vcodec_mem *bs_src;
> > > +       struct mtk_video_dec_buf *dec_buf_src;
> > > +       struct media_request *src_buf_req;
> > > +       struct vdec_fb *dst_buf;
> > > +       bool res_chg = false;
> > > +       int ret;
> > > +
> > > +       vb2_v4l2_src = v4l2_m2m_next_src_buf(ctx->m2m_ctx);
> > > +       if (vb2_v4l2_src == NULL) {
> > > +               v4l2_m2m_job_finish(dev->m2m_dev_dec, ctx->m2m_ctx);
> > > +               mtk_v4l2_debug(1, "[%d] no available source buffer", ctx-
> > > >id);
> > > +               return;
> > > +       }
> > > +
> > > +       vb2_v4l2_dst = v4l2_m2m_next_dst_buf(ctx->m2m_ctx);
> > > +       if (vb2_v4l2_dst == NULL) {
> > > +               v4l2_m2m_job_finish(dev->m2m_dev_dec, ctx->m2m_ctx);
> > > +               mtk_v4l2_debug(1, "[%d] no available destination buffer",
> > > ctx->id);
> > > +               return;
> > > +       }
> > > +
> > > +       vb2_src = &vb2_v4l2_src->vb2_buf;
> > > +       dec_buf_src = container_of(vb2_v4l2_src, struct mtk_video_dec_buf,
> > > +                                  m2m_buf.vb);
> > > +       bs_src = &dec_buf_src->bs_buffer;
> > > +
> > > +       mtk_v4l2_debug(3, "[%d] (%d) id=%d, vb=%p buf_info = %p",
> > > +                       ctx->id, src_buf->vb2_queue->type,
> > > +                       src_buf->index, src_buf, src_buf_info);
> > > +
> > > +       bs_src->va = vb2_plane_vaddr(vb2_src, 0);
> > > +       bs_src->dma_addr = vb2_dma_contig_plane_dma_addr(vb2_src, 0);
> > > +       bs_src->size = (size_t)vb2_src->planes[0].bytesused;
> > > +       if (!bs_src->va) {
> > > +               v4l2_m2m_job_finish(dev->m2m_dev_dec, ctx->m2m_ctx);
> > > +               mtk_v4l2_err("[%d] id=%d source buffer is NULL", ctx->id,
> > > +                            vb2_src->index);
> > > +               return;
> > > +       }
> > > +
> > > +       mtk_v4l2_debug(3, "[%d] Bitstream VA=%p DMA=%pad Size=%zx vb=%p",
> > > +                       ctx->id, buf->va, &buf->dma_addr, buf->size,
> > > src_buf);
> > > +       /* Apply request controls. */
> > > +       src_buf_req = vb2_src->req_obj.req;
> > > +       if (src_buf_req)
> > > +               v4l2_ctrl_request_setup(src_buf_req, &ctx->ctrl_hdl);
> > > +       else
> > > +               mtk_v4l2_err("vb2 buffer media request is NULL");
> > > +
> > > +       dst_buf = vdec_get_cap_buffer(ctx, vb2_v4l2_dst);
> > > +       v4l2_m2m_buf_copy_metadata(vb2_v4l2_src, vb2_v4l2_dst, true);
> > > +       ret = vdec_if_decode(ctx, bs_src, dst_buf, &res_chg);
> > > +       if (ret) {
> > > +               mtk_v4l2_err(
> > > +                       " <===[%d], src_buf[%d] sz=0x%zx pts=%llu
> > > vdec_if_decode() ret=%d res_chg=%d===>",
> > > +                       ctx->id, vb2_src->index, bs_src->size,
> > > +                       vb2_src->timestamp, ret, res_chg);
> > > +               if (ret == -EIO) {
> > > +                       mutex_lock(&ctx->lock);
> > > +                       dec_buf_src->error = true;
> > > +                       mutex_unlock(&ctx->lock);
> > > +               }
> > > +       }
> > > +
> > > +       mtk_vdec_stateless_set_dst_payload(ctx, dst_buf);
> > > +
> > > +       v4l2_m2m_buf_done_and_job_finish(dev->m2m_dev_dec, ctx->m2m_ctx,
> > > +               ret ? VB2_BUF_STATE_ERROR : VB2_BUF_STATE_DONE);
> > > +
> > > +       v4l2_ctrl_request_complete(src_buf_req, &ctx->ctrl_hdl);
> > > +}
> > > +
> > > +static void vb2ops_vdec_stateless_buf_queue(struct vb2_buffer *vb)
> > > +{
> > > +       struct mtk_vcodec_ctx *ctx = vb2_get_drv_priv(vb->vb2_queue);
> > > +       struct vb2_v4l2_buffer *vb2_v4l2 = to_vb2_v4l2_buffer(vb);
> > > +
> > > +       mtk_v4l2_debug(3, "[%d] (%d) id=%d, vb=%p",
> > > +                       ctx->id, vb->vb2_queue->type,
> > > +                       vb->index, vb);
> > > +
> > > +       mutex_lock(&ctx->lock);
> > > +       v4l2_m2m_buf_queue(ctx->m2m_ctx, vb2_v4l2);
> > > +       mutex_unlock(&ctx->lock);
> > > +       if (vb->vb2_queue->type != V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE)
> > > +               return;
> > > +
> > > +       mtk_v4l2_debug(3, "(%d) id=%d, bs=%p",
> > > +               vb->vb2_queue->type, vb->index, src_buf);
> > > +
> > > +       /* If an OUTPUT buffer, we may need to update the state */
> > > +       if (ctx->state == MTK_STATE_INIT) {
> > > +               ctx->state = MTK_STATE_HEADER;
> > > +               mtk_v4l2_debug(1, "Init driver from init to header.");
> > 
> > This state thing seems just something to make the rest
> > of the stateful-based driver happy, right?
> 
> Correct - if anything we should either use more of the state here
> (i.e. set the error state when relevant) or move the state entirely in
> the stateful part of the driver.
> 
> > 
> > Makes me wonder a bit if just splitting the stateless part to its
> > own driver, wouldn't make your maintenance easier.
> > 
> > What's the motivation for sharing the driver?
> 
> Technically you could do it both ways. Separating the driver would
> result in some boilerplate code and buffer-management structs
> duplication (unless we keep the shared part under another module - but
> in this case we are basically in the same situation as now). Also
> despite using different userspace-facing ABIs, MT8173 and MT8183
> follow a similar architecture and a similar firmware interface.
> Considering these similarities it seems simpler from an architectural
> point of view to have all the Mediatek codec support under the same
> driver. It also probably results in less code.
> 
> That being said, the split can probably be improved as you pointed out
> with this state variable. But the current split is not too bad IMHO,
> at least not worse than how the code was originally.
> 
> > 
> > > +       } else {
> > > +               mtk_v4l2_debug(3, "[%d] already init driver %d",
> > > +                               ctx->id, ctx->state);
> > > +       }
> > > +}
> > > +
> > > +static int mtk_vdec_flush_decoder(struct mtk_vcodec_ctx *ctx)
> > > +{
> > > +       bool res_chg;
> > > +
> > > +       return vdec_if_decode(ctx, NULL, NULL, &res_chg);
> > > +}
> > > +
> > > +static const struct v4l2_ctrl_ops mtk_vcodec_dec_ctrl_ops = {
> > > +       .g_volatile_ctrl = mtk_vdec_g_v_ctrl,
> > > +};
> > > +
> > > +static int mtk_vcodec_dec_ctrls_setup(struct mtk_vcodec_ctx *ctx)
> > > +{
> > > +       struct v4l2_ctrl *ctrl;
> > > +       unsigned int i;
> > > +
> > > +       v4l2_ctrl_handler_init(&ctx->ctrl_hdl, NUM_CTRLS);
> > > +       if (ctx->ctrl_hdl.error) {
> > > +               mtk_v4l2_err("v4l2_ctrl_handler_init failed\n");
> > > +               return ctx->ctrl_hdl.error;
> > > +       }
> > > +
> > > +       ctrl = v4l2_ctrl_new_std(&ctx->ctrl_hdl,
> > > +                               &mtk_vcodec_dec_ctrl_ops,
> > > +                               V4L2_CID_MIN_BUFFERS_FOR_CAPTURE,
> > > +                               0, 32, 1, 1);
> > > +       ctrl->flags |= V4L2_CTRL_FLAG_VOLATILE;
> > 
> > Hm, this volatile control for MIN_BUFFERS_FOR_CAPTURE seems
> > to return the DPB size. However, isn't this something userspace already
> > knows?
> 
> True, but that's also a control the driver is supposed to provide per
> the spec IIUC.
> 
> > 
> > > +
> > > +       for (i = 0; i < NUM_CTRLS; i++) {
> > > +               struct v4l2_ctrl_config cfg =
> > > mtk_stateless_controls[i].cfg;
> > > +
> > > +               v4l2_ctrl_new_custom(&ctx->ctrl_hdl, &cfg, NULL);
> > > +               if (ctx->ctrl_hdl.error) {
> > > +                       mtk_v4l2_err("Adding control %d failed %d",
> > > +                                       i, ctx->ctrl_hdl.error);
> > > +                       return ctx->ctrl_hdl.error;
> > > +               }
> > > +       }
> > > +
> > > +       v4l2_ctrl_handler_setup(&ctx->ctrl_hdl);
> > > +
> > > +       return 0;
> > > +}
> > > +
> > > +const struct media_device_ops mtk_vcodec_media_ops = {
> > > +       .req_validate   = fops_media_request_validate,
> > > +       .req_queue      = v4l2_m2m_request_queue,
> > > +};
> > > +
> > > +static void mtk_init_vdec_params(struct mtk_vcodec_ctx *ctx)
> > > +{
> > > +       struct vb2_queue *src_vq;
> > > +
> > > +       src_vq = v4l2_m2m_get_vq(ctx->m2m_ctx,
> > > +                                V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE);
> > > +
> > > +       /* Support request api for output plane */
> > > +       src_vq->supports_requests = true;
> > > +       src_vq->requires_requests = true;
> > > +}
> > > +
> > > +static int vb2ops_vdec_out_buf_validate(struct vb2_buffer *vb)
> > > +{
> > 
> > I have to admit I do not remember exactly the reason,
> > but this should set the buffer field to V4L2_FIELD_NONE.
> 
> Right, I see all other drivers are doing this. Done.
> 
> Cheers,
> Alex.