Re: [REGRESSION] breakage in sun6i-csi media api

[Paul Kocialkowski <paul.kocialkowski@bootlin.com>]

[-- Attachment #1: Type: text/plain, Size: 2581 bytes --]

Hi,

(Re-adding folks from the original email, adding Laurent and Hans.)

On Fri 02 Jun 23, 11:24, Martijn Braam wrote:
> Hi Paul,
> 
> That's basically it yes. My software doesn't expect the bridge block,
> because it wasn't there. The pipeline always worked "automatically".
> 
> This is the workaround that's been made now it run on newer kernels:
> https://gitlab.com/postmarketOS/megapixels/-/merge_requests/31
> 
> I'm pretty sure format propagation would fix this issue.

Okay that's good to know.

To be honest it's still not very clear to me if in-driver format propagation is
a "nice to have" feature or something that all media pipeline drivers are
supposed to implement.

Anyway I feel like this is not really a regression but a result of the driver
being converted to a newer API.

Also there's a V4L2_CAP_IO_MC flag which should indicate that the video device
must be controlled via the media controller API instead of being
video-device-centric, but I've seen comments asking not to set the flag even
when MC is used so I'm a bit confused here. Perhaps the flag is only required
when there is no automatic format propagation?

If anyone has solid answers on these points I'd be happy to read some
clarification (and act accordingly).

Cheers,

Paul

> Greetings,
> Martijn
> 
> On 6/2/23 11:16, Paul Kocialkowski wrote:
> > Hi Martijn,
> > 
> > On Thu 01 Jun 23, 23:19, Martijn Braam wrote:
> > > It seems like this commit:
> > > 
> > > media: sun6i-csi: Add bridge v4l2 subdev with port management
> > > 
> > > Has changed the way the media pipeline on a64 devices, in my case the PINE64
> > > PinePhone works. Since this is an API towards userspace and there's active
> > > applications that use it I think this counts as a regression.
> > Do you have more details on what changed specifically?
> > 
> > The commit added a bridge subdev in addition to the video node, which is
> > generally a better description of the CSI hardware and also a necessity
> > to support the ISP data flow.
> > 
> > Maybe your userspace application is not configuring the bridge media block with
> > the right format, which results in a mismatch?
> > 
> > Some work was started to achieve automatic format propagation, perhaps it
> > would be enough to solve your issue.
> > 
> > Cheers,
> > 
> > Paul
> > 
> > > #regzbot introduced: 0d2b746b1bef73de62d2d311e594a7ffed4ca43
> > > 
> > > Greetings,
> > > Martijn Braam

-- 
Paul Kocialkowski, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 488 bytes --]