linux-kernel - Re: [PATCH] staging: media: rkisp1: make links immutable by default

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Date:   Fri, 17 Jan 2020 23:36:34 +0100
From:   Niklas Söderlund 
        <niklas.soderlund@...natech.se>
To:     Helen Koike <helen.koike@...labora.com>
Cc:     linux-media@...r.kernel.org, hverkuil-cisco@...all.nl,
        kernel@...labora.com, laurent.pinchart@...asonboard.com,
        tfiga@...omium.org, Mauro Carvalho Chehab <mchehab@...nel.org>,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] staging: media: rkisp1: make links immutable by default

Hi Helen,

Thanks for your work.

On 2020-01-17 17:12:18 -0300, Helen Koike wrote:
> The only places which make sese to allow users to enable or disable
> links are:
> 
> * between sensors and isp:
> So users can select which sensor should be used while streaming
> 
> * between isp and the resizers:
>               |
>               v here
> rkisp1_isp:2 -> rkisp1_resizer_mainpath -> rkisp1_mainpath (capture)
>             \-> rkisp1_resizer_selfpath -> rkisp1_selfpath (capture)
>               ^ here
>               |
> 
> So users can disable one of the capture paths when unused, to avoid
> worring about matching formats.
> 
> Make the following links immutable to simplify userspace:
> 
> rkisp1_resizer_mainpath -> rkisp1_mainpath
> rkisp1_resizer_selfpath -> rkisp1_selfpath
> rkisp1_params           -> rkisp1_isp
> rkisp1_isp              -> rkisp1_stats
> 
> Signed-off-by: Helen Koike <helen.koike@...labora.com>
> 
> ---
> This is the topology graph after disabling all the links with
> media -r
> http://col.la/rkisp1immutable
> 
> Dashed links are the only one can can be enabled/disabled, the others
> are immutable.
> 
>  drivers/staging/media/rkisp1/rkisp1-dev.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/media/rkisp1/rkisp1-dev.c b/drivers/staging/media/rkisp1/rkisp1-dev.c
> index 558126e66465..4030d5e71af1 100644
> --- a/drivers/staging/media/rkisp1/rkisp1-dev.c
> +++ b/drivers/staging/media/rkisp1/rkisp1-dev.c
> @@ -145,14 +145,15 @@ static int rkisp1_create_links(struct rkisp1_device *rkisp1)
>  		flags = 0;
>  	}
>  
> -	flags = MEDIA_LNK_FL_ENABLED;
> +	flags = MEDIA_LNK_FL_ENABLED | MEDIA_LNK_FL_IMMUTABLE;
>  
>  	/* create ISP->RSZ->CAP links */
>  	for (i = 0; i < 2; i++) {
>  		source = &rkisp1->isp.sd.entity;
>  		sink = &rkisp1->resizer_devs[i].sd.entity;

nit: To keep with the style of the rest of the function I would set 
flags here and once more bellow in the same loop.

With or without this fixed,

Reviewed-by: Niklas Söderlund <niklas.soderlund@...natech.se>

>  		ret = media_create_pad_link(source, RKISP1_ISP_PAD_SOURCE_VIDEO,
> -					    sink, RKISP1_RSZ_PAD_SINK, flags);
> +					    sink, RKISP1_RSZ_PAD_SINK,
> +					    MEDIA_LNK_FL_ENABLED);
>  		if (ret)
>  			return ret;
>  
> -- 
> 2.24.0
> 

-- 
Regards,
Niklas Söderlund