Re: [PATCH 3/7] [Media] vcodec: mediatek: Add Mediatek V4L2 Video Decoder Driver

[tiffany lin <tiffany.lin@mediatek.com>]

Hi Hans,

On Mon, 2016-04-18 at 09:32 +0200, Hans Verkuil wrote:
> On 04/18/2016 07:40 AM, tiffany lin wrote:
> > 
> > snipped.
> > 
> >>> +
> >>> +void mtk_vcodec_dec_set_default_params(struct mtk_vcodec_ctx *ctx)
> >>> +{
> >>> +	struct mtk_q_data *q_data;
> >>> +
> >>> +	ctx->m2m_ctx->q_lock = &ctx->dev->dev_mutex;
> >>> +	ctx->fh.m2m_ctx = ctx->m2m_ctx;
> >>> +	ctx->fh.ctrl_handler = &ctx->ctrl_hdl;
> >>> +	INIT_WORK(&ctx->decode_work, mtk_vdec_worker);
> >>> +
> >>> +	q_data = &ctx->q_data[MTK_Q_DATA_SRC];
> >>> +	memset(q_data, 0, sizeof(struct mtk_q_data));
> >>> +	q_data->visible_width = DFT_CFG_WIDTH;
> >>> +	q_data->visible_height = DFT_CFG_HEIGHT;
> >>> +	q_data->fmt = &mtk_video_formats[OUT_FMT_IDX];
> >>> +	q_data->colorspace = V4L2_COLORSPACE_REC709;
> >>> +	q_data->field = V4L2_FIELD_NONE;
> >>> +	ctx->q_data[MTK_Q_DATA_DST].sizeimage[0] =
> >>> +		DFT_CFG_WIDTH * DFT_CFG_HEIGHT;
> >>> +	ctx->q_data[MTK_Q_DATA_DST].bytesperline[0] = 0;
> >>> +
> >>> +
> >>> +	q_data = &ctx->q_data[MTK_Q_DATA_DST];
> >>> +	memset(q_data, 0, sizeof(struct mtk_q_data));
> >>> +	q_data->visible_width = DFT_CFG_WIDTH;
> >>> +	q_data->visible_height = DFT_CFG_HEIGHT;
> >>> +	q_data->coded_width = DFT_CFG_WIDTH;
> >>> +	q_data->coded_height = DFT_CFG_HEIGHT;
> >>> +	q_data->colorspace = V4L2_COLORSPACE_REC709;
> >>> +	q_data->field = V4L2_FIELD_NONE;
> >>> +
> >>> +	q_data->fmt = &mtk_video_formats[CAP_FMT_IDX];
> >>> +
> >>> +	v4l_bound_align_image(&q_data->coded_width,
> >>> +					MTK_VDEC_MIN_W,
> >>> +					MTK_VDEC_MAX_W, 4,
> >>> +					&q_data->coded_height,
> >>> +					MTK_VDEC_MIN_H,
> >>> +					MTK_VDEC_MAX_H, 5, 6);
> >>> +
> >>> +	q_data->sizeimage[0] = q_data->coded_width * q_data->coded_height;
> >>> +	q_data->bytesperline[0] = q_data->coded_width;
> >>> +	q_data->sizeimage[1] = q_data->sizeimage[0] / 2;
> >>> +	q_data->bytesperline[1] = q_data->coded_width;
> >>> +
> >>> +}
> >>> +
> >>> +static int vidioc_vdec_streamon(struct file *file, void *priv,
> >>> +				enum v4l2_buf_type type)
> >>> +{
> >>> +	struct mtk_vcodec_ctx *ctx = fh_to_ctx(priv);
> >>> +
> >>> +	mtk_v4l2_debug(3, "[%d] (%d)", ctx->idx, type);
> >>> +
> >>> +	return v4l2_m2m_streamon(file, ctx->m2m_ctx, type);
> >>> +}
> >>> +
> >>> +static int vidioc_vdec_streamoff(struct file *file, void *priv,
> >>> +				 enum v4l2_buf_type type)
> >>> +{
> >>> +	struct mtk_vcodec_ctx *ctx = fh_to_ctx(priv);
> >>> +
> >>> +	mtk_v4l2_debug(3, "[%d] (%d)", ctx->idx, type);
> >>> +	return v4l2_m2m_streamoff(file, ctx->m2m_ctx, type);
> >>> +}
> >>> +
> >>> +static int vidioc_vdec_reqbufs(struct file *file, void *priv,
> >>> +			       struct v4l2_requestbuffers *reqbufs)
> >>> +{
> >>> +	struct mtk_vcodec_ctx *ctx = fh_to_ctx(priv);
> >>> +	int ret;
> >>> +
> >>> +	mtk_v4l2_debug(3, "[%d] (%d) count=%d", ctx->idx,
> >>> +			 reqbufs->type, reqbufs->count);
> >>> +	ret = v4l2_m2m_reqbufs(file, ctx->m2m_ctx, reqbufs);
> >>> +
> >>> +	return ret;
> >>> +}
> >>
> >> Please use the v4l2_m2m_ioctl_* helper functions were applicable.
> >>
> > 
> > 
> > 
> > snipped.
> >>> +static unsigned int fops_vcodec_poll(struct file *file,
> >>> +				     struct poll_table_struct *wait)
> >>> +{
> >>> +	struct mtk_vcodec_ctx *ctx = fh_to_ctx(file->private_data);
> >>> +	struct mtk_vcodec_dev *dev = ctx->dev;
> >>> +	int ret;
> >>> +
> >>> +	mutex_lock(&dev->dev_mutex);
> >>> +	ret = v4l2_m2m_poll(file, ctx->m2m_ctx, wait);
> >>> +	mutex_unlock(&dev->dev_mutex);
> >>> +
> >>> +	return ret;
> >>> +}
> >>> +
> >>> +static int fops_vcodec_mmap(struct file *file, struct vm_area_struct *vma)
> >>> +{
> >>> +	struct mtk_vcodec_ctx *ctx = fh_to_ctx(file->private_data);
> >>> +
> >>> +	return v4l2_m2m_mmap(file, ctx->m2m_ctx, vma);
> >>> +}
> >>> +
> >>> +static const struct v4l2_file_operations mtk_vcodec_fops = {
> >>> +	.owner				= THIS_MODULE,
> >>> +	.open				= fops_vcodec_open,
> >>> +	.release			= fops_vcodec_release,
> >>> +	.poll				= fops_vcodec_poll,
> >>> +	.unlocked_ioctl			= video_ioctl2,
> >>> +	.mmap				= fops_vcodec_mmap,
> >>
> >> You should be able to use the v4l2_m2m_fop helper functions for poll and mmap.
> >>
> > 
> > Hi Hans,
> > 
> > We are plaining to remove m2m framework in th feature, although we think
> 
> Remove it for just the decoder driver or both encoder and decoder?
> 
Remove it from decoder driver.

> > it is easy to use and could save a lot of code similar to what m2m
> > framework implemented and reduce code size.
> > The main reason is that in v4l2_m2m_try_schedule, it required that at
> > least one output buffer and one capture buffer to run device_run.
> > We want to start device_run without capture buffer queued.
> 
> I assume the reason is that you need to get the resolution etc. information
> from the encoded stream? Without a capture buffer you can't actually decode
> a frame, but that's probably not what this is about.
Yes, it could start parsing without waiting CAPTURE ready and get
CAPTURE buffer from vb2 when it really need it.


> > Is there any suggestion that we could use m2m framework but trigger
> > device_run with only output buffer.
> > Or we need to remove m2m and write our own implementation.
> 
> I am assuming that not using the m2m framework is for the decoder only and
> that its purpose is to obtain data about the encoded stream early.
> 
yes. it's for decode only.


> This is something that was discussed with Pawel in the past. I don't have a
> problem if you do it yourself (without the m2m framework), but it might also
> be an idea to adapt the framework for this.
> 
> Pawel, do you have any thoughts on that?
> 
> Regards,
> 
> 	Hans