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Message-ID: <AM6PR04MB6341DAEF2FCC3CB48A7F7E19E7FA9@AM6PR04MB6341.eurprd04.prod.outlook.com>
Date: Wed, 27 Apr 2022 07:01:07 +0000
From: Ming Qian <ming.qian@....com>
To: Hans Verkuil <hverkuil-cisco@...all.nl>,
"mchehab@...nel.org" <mchehab@...nel.org>,
"shawnguo@...nel.org" <shawnguo@...nel.org>
CC: "robh+dt@...nel.org" <robh+dt@...nel.org>,
"s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
"kernel@...gutronix.de" <kernel@...gutronix.de>,
"festevam@...il.com" <festevam@...il.com>,
dl-linux-imx <linux-imx@....com>,
Aisheng Dong <aisheng.dong@....com>,
"linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>
Subject: RE: [EXT] Re: [PATCH] media: amphion: ensure the buffer count is not
less than min_buffer
> From: Hans Verkuil [mailto:hverkuil-cisco@...all.nl]
> Sent: Wednesday, April 27, 2022 2:38 PM
> To: Ming Qian <ming.qian@....com>; mchehab@...nel.org;
> shawnguo@...nel.org
> Cc: robh+dt@...nel.org; s.hauer@...gutronix.de; kernel@...gutronix.de;
> festevam@...il.com; dl-linux-imx <linux-imx@....com>; Aisheng Dong
> <aisheng.dong@....com>; linux-media@...r.kernel.org;
> linux-kernel@...r.kernel.org; linux-arm-kernel@...ts.infradead.org
> Subject: [EXT] Re: [PATCH] media: amphion: ensure the buffer count is not less
> than min_buffer
>
> Caution: EXT Email
>
> Hi Ming Qian,
>
> On 22/03/2022 09:28, Ming Qian wrote:
> > the output buffer count should >= min_buffer_out the capture buffer
> > count should >= min_buffer_cap
> >
> > Signed-off-by: Ming Qian <ming.qian@....com>
> > ---
> > drivers/media/platform/amphion/vpu_v4l2.c | 4 ++++
> > 1 file changed, 4 insertions(+)
> >
> > diff --git a/drivers/media/platform/amphion/vpu_v4l2.c
> > b/drivers/media/platform/amphion/vpu_v4l2.c
> > index cbf3315605a9..72a0544f4da3 100644
> > --- a/drivers/media/platform/amphion/vpu_v4l2.c
> > +++ b/drivers/media/platform/amphion/vpu_v4l2.c
> > @@ -355,6 +355,10 @@ static int vpu_vb2_queue_setup(struct vb2_queue
> *vq,
> > return 0;
> > }
> >
> > + if (V4L2_TYPE_IS_OUTPUT(vq->type))
> > + *buf_count = max_t(unsigned int, *buf_count,
> inst->min_buffer_out);
> > + else
> > + *buf_count = max_t(unsigned int, *buf_count,
> > + inst->min_buffer_cap);
>
> I noticed that min_buffer_out/cap is set to 2, but min_buffers_needed is set to
> 1. Wouldn't it make more sense to set min_buffers_needed to
> 2 as well?
>
> If you do that, then the vb2 core will already take care of ensuring that the
> buf_count is adjusted.
>
> If you *do* have to do this manually, then you need to place the whole if-else
> under 'if (!*num_planes) {', otherwise it will mess up the VIDIOC_CREATE_BUFS
> ioctl. See the queue_setup in include/media/videobuf2-core.h documentation
> for the sordid details.
>
> Regards,
>
> Hans
>
Hi Hans,
I want to make the vpu start when 1 frames is queued, so I set the min_buffers_needed to 1.
And the min_buffer_cap may be changed when a source change event is triggered. So in most case, it will be larger than 2.
I'll make a v2 patch that place the whole if-else under 'if (!*num_planes) {'
Thanks for your reminder
Ming
> > *plane_count = cur_fmt->num_planes;
> > for (i = 0; i < cur_fmt->num_planes; i++)
> > psize[i] = cur_fmt->sizeimage[i];
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