[Question]: What's right way to use struct media_pipeline?

[Question]: What's right way to use struct media_pipeline?

[Bryan Wu]

Hi Hans,

I found struct media_pipeline actually is completely empty and I assume 
we use that to control all the entities belonging to one media_pipeline.

media_pipeline should contains either all the media_link or all the 
media_entity. How come an empty struct can provide those information?

What about following ideas?
1. when media_entity_create_links, it will return a media_link pointer.
2. we save this media_link pointer into the media_pipeline
3. use this media_pipeline for start streaming, stop streaming and 
validate links.

Maybe I miss something during recent media controller changes.

Thanks,
-Bryan

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Re: [Question]: What's right way to use struct media_pipeline?

[Hans Verkuil]

On 09/24/2015 02:55 AM, Bryan Wu wrote:
> Hi Hans,
> 
> I found struct media_pipeline actually is completely empty and I assume we use that to control all the entities belonging to one media_pipeline.
> 
> media_pipeline should contains either all the media_link or all the media_entity. How come an empty struct can provide those information?

It's basically an empty base class to speak in C++ terminology.

See drivers/media/platform/xilinx/xilinx-dma.h on how it is used there.

Laurent Pinchart knows a lot more about it than I do, though.

Regards,

	Hans

> 
> What about following ideas?
> 1. when media_entity_create_links, it will return a media_link pointer.
> 2. we save this media_link pointer into the media_pipeline
> 3. use this media_pipeline for start streaming, stop streaming and validate links.
> 
> Maybe I miss something during recent media controller changes.
> 
> Thanks,
> -Bryan
> 
> -----------------------------------------------------------------------------------
> This email message is for the sole use of the intended recipient(s) and may contain
> confidential information.  Any unauthorized review, use, disclosure or distribution
> is prohibited.  If you are not the intended recipient, please contact the sender by
> reply email and destroy all copies of the original message.
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Re: [Question]: What's right way to use struct media_pipeline?

[Bryan Wu]

On 09/24/2015 01:47 AM, Hans Verkuil wrote:
> On 09/24/2015 02:55 AM, Bryan Wu wrote:
>> Hi Hans,
>>
>> I found struct media_pipeline actually is completely empty and I assume we use that to control all the entities belonging to one media_pipeline.
>>
>> media_pipeline should contains either all the media_link or all the media_entity. How come an empty struct can provide those information?
> It's basically an empty base class to speak in C++ terminology.
>
> See drivers/media/platform/xilinx/xilinx-dma.h on how it is used there.
>
> Laurent Pinchart knows a lot more about it than I do, though.
>

Hi Laurent,

I have a subdev media entity which have 4 media pads.

pad[0] is sink and pad[1] is source, these 2 pads belong to the first 
media pipeline

pad[2] is sink and pad[3] is source, these 2 pads belong to the second 
media pipeline

Actually our hardware Tegra has 3 these kind of entities, so totally we 
have 6 media pipelines like 6 dma channels.

How to handle that with media pipeline framework? I saw in xilinx driver 
it just has one pipeline which is shared by several DMA channels, right?

-Bryan

>
>> What about following ideas?
>> 1. when media_entity_create_links, it will return a media_link pointer.
>> 2. we save this media_link pointer into the media_pipeline
>> 3. use this media_pipeline for start streaming, stop streaming and validate links.
>>
>> Maybe I miss something during recent media controller changes.
>>
>> Thanks,
>> -Bryan
>>
>> -----------------------------------------------------------------------------------
>> This email message is for the sole use of the intended recipient(s) and may contain
>> confidential information.  Any unauthorized review, use, disclosure or distribution
>> is prohibited.  If you are not the intended recipient, please contact the sender by
>> reply email and destroy all copies of the original message.
>> -----------------------------------------------------------------------------------