[libcamera-devel] [PATCH v2 2/2] pipeline: raspberrypi: Add support for Video Mux and Bridge devices
Laurent Pinchart
laurent.pinchart at ideasonboard.com
Fri Dec 10 01:24:28 CET 2021
Hi Naush,
On Thu, Dec 09, 2021 at 10:29:21AM +0000, Naushir Patuck wrote:
> On Thu, 9 Dec 2021 at 10:25, Kieran Bingham wrote:
> > Quoting Naushir Patuck (2021-12-09 10:07:43)
> > > On Thu, 9 Dec 2021 at 09:39, Kieran Bingham wrote:
> > > > Quoting Naushir Patuck (2021-12-08 15:15:27)
> > > > > This change will allow the pipeline handler to enumerate and control Video
> > > > > Mux or Bridge devices that may be attached between sensors and a particular
> > > > > Unicam instance. Cascaded mux or bridge devices are also handled.
> > > > >
> > > > > A new member function enumerateVideoDevices(), called from registerCamera(), is
> > > > > used to identify and open all mux and bridge subdevices present in the
> > > > > sensor -> Unicam link.
> > > > >
> > > > > Relevent links are enabled/disabled and pad formats correctly set in configure()
> > > > > before the camera is started.
> > > > >
> > > > > Signed-off-by: Naushir Patuck <naush at raspberrypi.com>
> > > > > ---
> > > > > .../pipeline/raspberrypi/raspberrypi.cpp | 78 +++++++++++++++++++
> > > > > 1 file changed, 78 insertions(+)
> > > > >
> > > > > diff --git a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > > > > index 756878c70036..ca176ecb40ec 100644
> > > > > --- a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > > > > +++ b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > > > > @@ -12,6 +12,7 @@
> > > > > #include <mutex>
> > > > > #include <queue>
> > > > > #include <unordered_set>
> > > > > +#include <utility>
> > > > >
> > > > > #include <libcamera/base/shared_fd.h>
> > > > > #include <libcamera/base/utils.h>
> > > > > @@ -220,6 +221,11 @@ public:
> > > > > std::vector<RPi::Stream *> streams_;
> > > > > /* Stores the ids of the buffers mapped in the IPA. */
> > > > > std::unordered_set<unsigned int> ipaBuffers_;
> > > > > + /*
> > > > > + * Stores a cascade of Video Mux or Bridge devices between the sensor and
> > > > > + * Unicam together with media link across the entities.
> > > > > + */
> > > > > + std::vector<std::pair<std::unique_ptr<V4L2Subdevice>, MediaLink *>> bridgeDevices_;
> > > > >
> > > > > /* DMAHEAP allocation helper. */
> > > > > RPi::DmaHeap dmaHeap_;
> > > > > @@ -311,6 +317,7 @@ private:
> > > > > }
> > > > >
> > > > > int registerCamera(MediaDevice *unicam, MediaDevice *isp, MediaEntity *sensorEntity);
> > > > > + void enumerateVideoDevices(RPiCameraData *data, MediaLink *link);
> > > > > int queueAllBuffers(Camera *camera);
> > > > > int prepareBuffers(Camera *camera);
> > > > > void freeBuffers(Camera *camera);
> > > > > @@ -868,6 +875,25 @@ int PipelineHandlerRPi::configure(Camera *camera, CameraConfiguration *config)
> > > > > */
> > > > > data->properties_.set(properties::ScalerCropMaximum, data->sensorInfo_.analogCrop);
> > > > >
> > > > > + /* Setup the Video Mux/Bridge entities. */
> > > > > + for (auto &[device, link] : data->bridgeDevices_) {
> > > > > + /* Start by disabling all the sink pad links on the devices in the cascade. */
> > > > > + for (const MediaPad *p : device->entity()->pads()) {
> > > > > + if (!(p->flags() & MEDIA_PAD_FL_SINK))
> > > > > + continue;
> > > > > +
> > > > > + for (MediaLink *l : p->links())
> > > > > + l->setEnabled(false);
As an optimization, you could skip disabling the link that you will
enable below.
> > > > > + }
> > > > > +
> > > > > + /* Finally enable the link, and setup the pad format. */
> > > > > + link->setEnabled(true);
> > > >
> > > > Isn't this going to enable /all/ bridge links in the cascade
> > > > incorrectly?
> > > >
> > > >
> > > > ┌──────────┐
> > > > │ Unicam │
> > > > └─────▲────┘
> > > > │
> > > > ┌───┴───┐
> > > > │ Mux ◄───────┐
> > > > └──▲────┘ │
> > > > │ │
> > > > ┌─────┴───┐ ┌───┴───┐
> > > > │ Sensor1 │ │ Mux │◄──┐
> > > > └─────────┘ └─▲─────┘ │
> > > > │ │
> > > > ┌───────┴─┐ ┌───┴─────┐
> > > > │ Sensor2 │ │ Sensor3 │
> > > > └─────────┘ └─────────┘
> > > >
> > > > In that 'use case' we're now iterating over all bridges and enabling
> > > > their link, I think which means we've just enabled both muxes,
> > > > immediately after disabling them - even for Sensor1?
> > > >
> > > > Maybe I've mis-understood it, but I thought there would be something
> > > > that would start at the desired sensor, and walk up the links to the
> > > > unicam enabling those links (and only those) as it went up?
> > > >
> > > > The walk only has to be done once too, so perhaps a per-camera(sensor)
> > > > vector of links to iterate and enable?
> > > >
> > > > Or maybe I'm missing the separation between the bridgeDevices_ and the
> > > > per-camera instances. But if that's already happening, I can't then see
> > > > how each camera data clears all the bridges used by other cameras...
> > >
> > > Let me explain my intention, and you can then tell me if the code does
> > > what I think it does :-)
> > >
> > > Each sensor (Sensor{1,2,3}) will register its own Camera object, and
> > > in that object bridgeDevices_ will store the cascade of muxes between
> > > the sensor and the Unicam port. So, for Sensor1, we store only 1 mux,
> > > and Sensor{2,3} will store both muxes. Together with the mux device,
> > > we also store the entity to entity links.
> > >
> > > The above code goes through those stored entities, first disabling *all*
> > > links on each device in the chain, and then selectively enabling
> > > the specific links that are stored in bridgeDevices_ to link sensor
> > > to Unicam across all intermedia muxes. If Sensor1 is used, this
> > > does mean that the Sensor{2,3} -> Mux links might not change
> > > state but the Mux to Mux link will be disabled. Similarly, if we are driving
> > > Sensor3, the Sensor{1,2} -> Mux link will be disabled.
> >
> > I think I see the obvious part I missed ;-)
> >
> > It doesn't matter what configuration Mux2 has as long as Mux1 only has
> > Sensor1 link enabled!
> >
> > It might help to document that in the comments somehow somewhere?
> > Particularly now that you've already written the explanation to me -
> > perhaps it should be a block comment above enumerateVideoDevices.
> >
> > Feel free to take or add the ascii diagram, I think more pictures in
> > our documentation are always helpful. It's really easy to make those
> > block diagrams in ascii art at https://asciiflow.com.
>
> Sure, I'll add some comments through the code explaining it in more detail.
>
> > > > > + const MediaPad *srcPad = link->sink();
> > > > > + ret = device->setFormat(srcPad->index(), &sensorFormat);
> > > >
> > > > This assignment of ret is in a loop, so earlier failures are going to
> > > > get ignored, unchecked.
> > >
> > > This should not matter, as ret is only used in the loop to count successful
> > > camera registrations. The return value from match() will be false only if
> > > 0 cameras were registered.
> >
> > So should we not even assign it?
> > Do we need to report a warning if it failed to set the format?
> >
> > But aren't we here in configure() setting the format of the device to
> > propogate the format?
> >
> > If we fail to setFormat in that case, then I think we should be saying
> > the configure() call failed?
>
> Oops, my mistake. I misread your original comment and what bit of
> code it refers to! This ret value *is* used for the return path, and must
> be accounted for correctly as it is set in a loop! I'll fix this in the next
> revision.
>
> > > > > + LOG(RPI, Info) << "Configured media link on device " << device->entity()->name()
> > > > > + << " at pad " << srcPad->index();
> > > > > + }
> > > > > +
> > > > > return ret;
> > > > > }
> > > > >
> > > > > @@ -1098,6 +1124,13 @@ int PipelineHandlerRPi::registerCamera(MediaDevice *unicam, MediaDevice *isp, Me
> > > > > if (data->sensor_->init())
> > > > > return -EINVAL;
> > > > >
> > > > > + /*
> > > > > + * Enumerate all the Video Mux/Bridge devices across the sensor -> unicam
> > > > > + * link. There may be a cascade of devices in this link!
> > > > > + */
> > > > > + MediaLink *link = sensorEntity->getPadByIndex(0)->links()[0];
> > > > > + enumerateVideoDevices(data.get(), link);
> > > > > +
> > > > > data->sensorFormats_ = populateSensorFormats(data->sensor_);
> > > > >
> > > > > ipa::RPi::SensorConfig sensorConfig;
> > > > > @@ -1224,6 +1257,51 @@ int PipelineHandlerRPi::registerCamera(MediaDevice *unicam, MediaDevice *isp, Me
> > > > > return 0;
> > > > > }
> > > > >
> > > > > +void PipelineHandlerRPi::enumerateVideoDevices(RPiCameraData *data, MediaLink *link)
This function accesses members of data but doesn't seem to access any
member of PipelineHandlerRPi. Could it be moved to RPiCameraData ?
> > > > > +{
> > > > > + const MediaPad *sinkPad = link->sink();
> > > > > + const MediaEntity *entity = sinkPad->entity();
> > > > > + bool unicamFound = false;
> > > > > +
> > > > > + /* We only deal with Video Mux and Bridge devices in cascade. */
> > > > > + if (entity->function() != MEDIA_ENT_F_VID_MUX &&
> > > > > + entity->function() != MEDIA_ENT_F_VID_IF_BRIDGE)
> > > > > + return;
> > > > > +
> > > > > + LOG(RPI, Info) << "Found video mux device " << entity->name()
> > > > > + << " linked to sink pad " << sinkPad->index();
> > > > > +
> > > > > + data->bridgeDevices_.emplace_back(std::make_unique<V4L2Subdevice>(entity),link);
> > > > > + data->bridgeDevices_.back().first->open();
> > > >
> > > > Going through the above, I can't help but wonder if the bridgeDevices_
> > > > should be stored as a single instance in the Pipeline handler (not each
> > > > CameraData, we have one CameraData per camera right? if so, how does
> > > > camera3 disable all the links? does it know about every path?)
> > >
> > > From my description earlier, bridgeDevices_ must be stored in the CameraData, as
> > > it lists the devices in the path between the sensor and Unicam. And this is unique
> > > per-sensor. Again, this does mean that if we are using Sensor1, links for Sensor{2,3}
> > > -> Mux are not changed, but the Mux->Mux link will be disabled. Do you think
> > > that may not be appropriate leaving them enabled?
I can't help but seeing lots of similarities with the simple pipeline
handler, which also performs dynamic discovery of pipelines (all the way
to the video node in that case, while in your case it would be all the
way to the Unicam device). I wonder if we could share code between the
two ? This could benefit the Raspberry Pi pipeline handler by providing
a more generic version of format propagation through the pipeline
(although that part may be more difficult to share).
An important difference between the two implementations is that the
simple pipeline handler opens the video node and subdevs once only,
storing them in the pipeline handler instance, and only stores pointers
to those objects in the camera data.
> > I missed that, and now it's obvious. If the first mux is only pointing
> > to Sensor1, then indeed it doesn't matter what mux2 is configured to
> > link to...
> >
> > So I think that's ok.
> >
> > > Please shout if this doesn't make sense, and something simpler might
> > > equally work :-)
> >
> > It's all fine until someone adds a crossbar perhaps that might make it
> > possible to do more crazy things ;-)
> >
> > But we don't need to worry about that now I dont' think.
> >
> > I think I'm still concerned about that ret during the loop in
> > configure(). But with that resolved:
> >
> > Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> >
> > > > > +
> > > > > + for (const MediaPad *pad : entity->pads()) {
> > > > > + /*
> > > > > + * Iterate through all the sink pads down the cascade to find any
> > > > > + * other Video Mux and Bridge devices.
> > > > > + */
> > > > > + if (!(pad->flags() & MEDIA_PAD_FL_SOURCE))
> > > > > + continue;
> > > > > +
> > > > > + for (MediaLink *l : pad->links()) {
> > > > > + enumerateVideoDevices(data, l);
> > > > > + if (l->sink()->entity()->name() == "unicam-image")
> > > > > + unicamFound = true;
> > > > > + }
> > > > > + }
> > > > > +
> > > > > + /* This identifies the end of our entity enumeration recursion. */
> > > > > + if (link->source()->entity()->function() == MEDIA_ENT_F_CAM_SENSOR) {
> > > > > + /*
> > > > > + * If Unicam is not at the end of this cascade, we cannot configure
> > > > > + * this topology automatically, so remove all entity references.
> > > > > + */
> > > > > + if (!unicamFound) {
> > > > > + LOG(RPI, Warning) << "Cannot automatically configure this MC topology!";
> > > > > + data->bridgeDevices_.clear();
> > > > > + }
> > > > > + }
> > > > > +}
> > > > > +
> > > > > int PipelineHandlerRPi::queueAllBuffers(Camera *camera)
> > > > > {
> > > > > RPiCameraData *data = cameraData(camera);
--
Regards,
Laurent Pinchart
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