Re: [PATCH 0/4] media: ti-vpe: cal: multiplexed streams support

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Tomi,

Thank you for the series. Nice to see the multiplexed streams API in
operation.

On Tue, Apr 27, 2021 at 04:20:24PM +0300, Tomi Valkeinen wrote:
> Hi,
> 
> This series adds embedded data and multiplexed streams support to TI CAL
> driver. These patches depend on the subdev routing series and CAL preparation
> series:
> 
> https://lore.kernel.org/linux-media/20210427124523.990938-1-tomi.valkeinen@ideasonboard.com/
> 
> https://lore.kernel.org/linux-media/20210420120433.902394-1-tomi.valkeinen@ideasonboard.com/
> 
> One detail I'm not too happy about is adding a new kernel module parameter
> 'cal_streams_api'. Setting this parameter enables the multiplexed streams
> support for the CAL sink pads. I'd like the driver to be able to figure this
> out itself, but there's no simple answer to it.
> 
> A pad in a subdev has to be either in non-multiplexed or multiplexed mode. If
> the subdev cannot support multiplexed streams, then the answer is clear. But if
> it can, then the question becomes "what's connected to the pad, and what does
> it want". Afaik, the idea with subdev configuration is that each subdev can be
> configured independently, so the driver trying to figure out the answer to that
> question breaks this idea. Also, two connected subdevs that both can support
> both modes wouldn't even give the answer, but the answer might be found further
> away, probably from the sensor subdev.
> 
> So, maybe it should be the userspace that can set a subdev pad to either of the
> modes. There's currently no such uAPI, but I think this option makes the most
> sense.

We'll need to brainstorm this a bit. I agree that the module parameter
isn't a good solution.

> Another detail to note is the embedded data support. I don't have hardware with
> real embedded data, so I have not added any embedded data formats. Also, the
> embedded data is captured with the video capture ioctls, not the metadata
> capture ioctls. The reason for this is that in the case of CSI-2 embedded data
> (at least for this hardware) the embedded data is very much like pixel data:
> the data is sent in lines just before or after the pixel content and each
> subdev needs a set_fmt call with the width, height, and mbus-code.
> 
> Using the metadata ioctls is possible, but it only results in much more complex
> driver code, and, I think, more confusing userspace.
> 
>  Tomi
> 
> Tomi Valkeinen (4):
>   media: ti-vpe: cal: add embedded data support
>   media: ti-vpe: cal: use frame desc to get vc and dt
>   media: ti-vpe: cal: add routing support
>   media: ti-vpe: cal: add multiplexed streams support
> 
>  drivers/media/platform/ti-vpe/cal-camerarx.c | 234 ++++++++++++++++---
>  drivers/media/platform/ti-vpe/cal-video.c    |  95 +++++++-
>  drivers/media/platform/ti-vpe/cal.c          | 102 ++++++--
>  drivers/media/platform/ti-vpe/cal.h          |  10 +-
>  4 files changed, 383 insertions(+), 58 deletions(-)

-- 
Regards,

Laurent Pinchart