Re: [PATCH v2 2/2] v4l: Add support for STD ioctls on subdev nodes

[Marco Felsch <m.felsch@pengutronix.de>]

Hi Javier,

On 18-07-13 11:18, Javier Martinez Canillas wrote:
> On 07/11/2018 12:39 PM, Marco Felsch wrote:
> > Hi Javier,
> > 
> > On 18-07-08 15:11, Javier Martinez Canillas wrote:
> >> [adding Marco Felsch since he has been working on this driver]
> >>
> >> On 07/05/2018 03:12 PM, Hans Verkuil wrote:
> >>> On 05/07/18 14:44, Mauro Carvalho Chehab wrote:
> >>>> Javier,
> >>>>
> >>>> How standard settings work with the current OMAP3 drivers with tvp5150?
> >>>
> >>> It looks like tvp5150 uses autodetect of the standard, which in general is
> >>
> >> That's correct, the driver uses standard autodetect.
> >>
> >>> not a good thing to do since different standards have different buffer
> >>> sizes. But this chip can scale, so it might scale PAL to NTSC or vice versa
> >>> if the standard switches mid-stream. Or it only detects the standard when
> >>> it starts streaming, I'm not sure.
> >>>
> >>
> >> Not sure about this either, IIUC switching the standard mid-stream won't work.
> > 
> > As far as I know, the detection happens after a sync lost event.
> >
> 
> Ah, good to know.
>  
> >>> In any case, this is not normal behavior, for almost all analog video
> >>> receivers you need to be able to set the std explicitly.
> >>>
> >>
> >> Indeed. I see that Marco's recent series [0] add supports for the .querystd [1]
> >> and .g_std [2] callbacks to the tvp5150 driver, so that way user-space can get
> >> back the detected standard.
> >>
> >> [0]: https://www.spinics.net/lists/linux-media/msg136869.html
> >> [1]: https://www.spinics.net/lists/linux-media/msg136872.html
> >> [2]: https://www.spinics.net/lists/linux-media/msg136875.html
> > 
> > I tought the std will be set by the v4l2_subdev_video_ops.s_std()
> > operation. If the user change the std manually, the autodection is
> > disabled.
> >
> 
> Yes, what I tried to say is that user-space won't have a way to know which std
> to set without a .querystd, or know what std was autodetected withou a .g_std.

Now I got you. Yes, thats the only way, as far as I know.

> Best regards,

Regards,
Marco