linux-kernel - Re: [PATCH v1 3/5] media: venus: do not destroy video session during queue setup

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Date:   Wed, 14 Nov 2018 20:02:10 +0900
From:   Tomasz Figa <tfiga@...omium.org>
To:     Stanimir Varbanov <stanimir.varbanov@...aro.org>
Cc:     sgorle@...eaurora.org, Hans Verkuil <hverkuil@...all.nl>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Alexandre Courbot <acourbot@...omium.org>,
        vgarodia@...eaurora.org
Subject: Re: [PATCH v1 3/5] media: venus: do not destroy video session during
 queue setup

On Fri, Nov 9, 2018 at 7:00 PM Stanimir Varbanov
<stanimir.varbanov@...aro.org> wrote:
>
> Hi Srinu,
>
> On 9/29/18 3:00 PM, Srinu Gorle wrote:
> > - open and close video sessions for plane properties is incorrect.
>
> Could you rephrase this statement? I really don't understand what you mean.
>
> > - add check to ensure, same instance persist from driver open to close.
>
> This assumption is wrong. The v4l client can change the codec by SFMT
> without close the device node, in that case we have to destroy and
> create a new session with new codec.

Right.

[snip]
> > +
> >       inst->hfi_codec = to_codec_type(pixfmt);
> >       reinit_completion(&inst->done);
> >
> > diff --git a/drivers/media/platform/qcom/venus/vdec.c b/drivers/media/platform/qcom/venus/vdec.c
> > index afe3b36..0035cf2 100644
> > --- a/drivers/media/platform/qcom/venus/vdec.c
> > +++ b/drivers/media/platform/qcom/venus/vdec.c
> > @@ -700,6 +700,8 @@ static int vdec_num_buffers(struct venus_inst *inst, unsigned int *in_num,
> >
> >       *out_num = HFI_BUFREQ_COUNT_MIN(&bufreq, ver);
> >
> > +     return 0;
>
> OK in present implementation I decided that the codec is settled when
> streamon on both queues is called (i.e. the final session_init is made
> in streamon). IMO the correct one is to init the session in
> reqbuf(output) and deinit session in reqbuf(output, count=0)?
>

Depending on what you mean by "settled" that could be fine.

Generally for initialization, one would typically use REQBUFS(OUTPUT,
>0) (since it's not possible to change the format after the
allocation) or STREAMON(OUTPUT) (to defer the hardware operations
until really necessary).

Since STREAMOFF(OUTPUT) is expected to just trigger a seek,
termination should be done in REQBUFS(OUTPUT, 0) indeed and after that
one should be able to switch to another codec (OUTPUT format).

Best regards,
Tomasz