Hi Steve, On Tue, Apr 11, 2017 at 05:50:58PM -0700, Steve Longerbeam wrote: > > > On 04/04/2017 05:47 AM, Sakari Ailus wrote: > >Hi Steve, Philipp and Pavel, > > > >On Mon, Mar 27, 2017 at 05:40:34PM -0700, Steve Longerbeam wrote: > >>From: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx> > >> > >>This driver can handle SoC internal and external video bus multiplexers, > >>controlled either by register bit fields or by a GPIO. The subdevice > >>passes through frame interval and mbus configuration of the active input > >>to the output side. > > > >The MUX framework is already in linux-next. Could you use that instead of > >adding new driver + bindings that are not compliant with the MUX framework? > >I don't think it'd be much of a change in terms of code, using the MUX > >framework appears quite simple. > > I would prefer to wait on this, and get what we have merged now so I can > unload all these patches first. The DT bindings will be different for this one and if you were using a MUX, won't they? And you can't remove support for the existing bindings either, you have to continue to support them going forward. > > Also this is Philipp's driver, so again I would prefer to get this > merged as-is and then Philipp can address these issues in a future > patch. But I will add my comments below... I bet there will be more issues to handle if you were to do the changes later than now. ... > >>+static int vidsw_s_stream(struct v4l2_subdev *sd, int enable) > >>+{ > >>+ struct vidsw *vidsw = v4l2_subdev_to_vidsw(sd); > >>+ struct v4l2_subdev *upstream_sd; > >>+ struct media_pad *pad; > >>+ > >>+ if (vidsw->active == -1) { > >>+ dev_err(sd->dev, "Can not start streaming on inactive mux\n"); > >>+ return -EINVAL; > >>+ } > >>+ > >>+ pad = media_entity_remote_pad(&sd->entity.pads[vidsw->active]); > >>+ if (!pad) { > >>+ dev_err(sd->dev, "Failed to find remote source pad\n"); > >>+ return -ENOLINK; > >>+ } > >>+ > >>+ if (!is_media_entity_v4l2_subdev(pad->entity)) { > >>+ dev_err(sd->dev, "Upstream entity is not a v4l2 subdev\n"); > >>+ return -ENODEV; > >>+ } > >>+ > >>+ upstream_sd = media_entity_to_v4l2_subdev(pad->entity); > >>+ > >>+ return v4l2_subdev_call(upstream_sd, video, s_stream, enable); > > > >Now that we'll have more than two drivers involved in the same pipeline it > >becomes necessary to define the behaviour of s_stream() throughout the > >pipeline --- i.e. whose responsibility is it to call s_stream() on the > >sub-devices in the pipeline? > > In the case of imx-media, the capture device calls set stream on the > whole pipeline in the start_streaming() callback. This subdev call is > actually a NOOP for imx-media, because the upstream entity has already > started streaming. Again I think this should be removed. It also > enforces a stream order that some MC drivers may have a problem with. What I want to say here is that the order in which the different devices in the pipeline need to be started may not be known in a driver for a particular part of the pipeline. In order to avoid trying to have a single point of decision making, the s_stream() op implemented in sub-device drivers should serve the purpose. I'll cc you for the documentation patch. -- Kind regards, Sakari Ailus e-mail: sakari.ailus@xxxxxx XMPP: sailus@xxxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html