Re: [RFC PATCH 1/3] [media] v4l2-mc.h: Add a S-Video C input PAD to demod enum

[Mauro Carvalho Chehab <mchehab@osg.samsung.com>]

Em Mon, 21 Mar 2016 16:48:12 -0300
Javier Martinez Canillas <javier@osg.samsung.com> escreveu:

> Hello Hans,
> 
> On 03/21/2016 04:30 PM, Hans Verkuil wrote:
> 
> [snip]
> 
> >>>>
> >>>> Can you please provide an example of a media pipeline that user-space should
> >>>> use with this approach? AFAICT whatever PADs are created when initiliazing
> >>>> the PADs for an entity, will be exposed to user-space in the media graph.
> >>>>
> >>>> So I'm not understading how it will be used in practice. I don't mean that
> >>>> your approach is not correct, is just I'm not getting it :)  
> >>>
> >>> Why would userspace need to use the pads? This is for legacy drivers (right?)
> >>> where the pipeline is fixed anyway.
> >>>  
> >>
> >> I asked because the user needs to setup the links in the media pipeline to
> >> choose  which input connection will be linked to the tvp5150 decoder. But it
> >> doesn't matter if we are going with the single sink pad approach since the
> >> user will always do something like:  
> > 
> > Why? The user will use an application that uses ENUM/S/G_INPUT for this. We're
> > talking legacy drivers ('interface centric drivers' would be a better description)
> > where we don't even expose the v4l-subdevX device nodes. Explicitly programming
> > a media pipeline is something you do for complex devices (embedded systems and
> > the like). Not for simple and generally fixed pipelines. Utterly pointless.
> >  
> 
> Mauro was talking about legacy 'interface centric' PC-consumer's hardware but
> my test system is an embedded board that also has a tvp5150 decoder. The
> board has an OMAP3 and the tvp5150 is attached to the SoC ISP. Is this one:
> 
> https://www.isee.biz/products/igep-expansion-boards/igepv2-expansion

Yeah, subdevs should be prepared to work with both "interface centric" and
"media controller centric" approaches.

Yet, I don't think using one sink pad for tvp5150 is a bad thing.

> As you can see, the board has 2 RCA connectors and each one is routed a tvp5150
> composite input and both connectors can be used for S-Video. So the user needs
> to setup the pipeline manually to choose which input connection to use.

Actually, on your tests, you were not able to make this work, nor
S-Video is officially supported by the manufacturer. So, in the
specific case of IGEPv2, I would not be adding a S-Video connector.

Btw, even on devices with an S-Video connector and tvp5150, at
least on my tests, the driver were not able to setup S-Video. It
seems that there's something more than just setting the mux.

- 
Thanks,
Mauro