[libcamera-devel] [PATCH] pipeline: raspberrypi: Iterate over all Unicam instances in match()
Naushir Patuck
naush at raspberrypi.com
Fri Mar 10 11:01:08 CET 2023
Hi Laurent,
On Thu, 9 Mar 2023 at 10:02, Laurent Pinchart <
laurent.pinchart at ideasonboard.com> wrote:
> Hi Naush,
>
> On Thu, Mar 09, 2023 at 08:04:47AM +0000, Naushir Patuck wrote:
> > On Thu, 9 Mar 2023 at 01:14, Laurent Pinchart wrote:
> >
> > > Hi Naush,
> > >
> > > Thank you for the patch.
> > >
> > > I know this has been merged, but I've noticed a few issues, which can
> be
> > > fixed in further patches.
> > >
> > > On Fri, Feb 24, 2023 at 07:30:23AM +0000, Naushir Patuck via
> libcamera-devel wrote:
> > > >
> > > > On Raspberry Pi Compute Module platforms, it is possible to attach a
> > > > single camera device only to the secondary Unicam port. The current
> > > > logic of PipelineHandlerRPi::match() will return a failure during
> > > > enumeration of the first Unicam media device (due to no sensor
> attached,
> > > > or sensor failure) and thus the second Unicam media device will
> never be
> > > > enumerated.
> > > >
> > > > Fix this by looping over all Unicam instances in
> PipelineHandlerRPi::match()
> > > > until a camera is correctly registered, or return a failure
> otherwise.
> > > >
> > > > Reported-on: https://github.com/raspberrypi/libcamera/issues/44
> > > > Signed-off-by: Naushir Patuck <naush at raspberrypi.com>
> > > > ---
> > > > .../pipeline/raspberrypi/raspberrypi.cpp | 67
> +++++++++++--------
> > > > 1 file changed, 40 insertions(+), 27 deletions(-)
> > > >
> > > > diff --git a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > > > index 841209548350..ef01b7e166ba 100644
> > > > --- a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > > > +++ b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > > > @@ -1246,41 +1246,54 @@ int
> PipelineHandlerRPi::queueRequestDevice(Camera *camera, Request *request)
> > > >
> > > > bool PipelineHandlerRPi::match(DeviceEnumerator *enumerator)
> > > > {
> > > > - DeviceMatch unicam("unicam");
> > > > - MediaDevice *unicamDevice = acquireMediaDevice(enumerator,
> unicam);
> > > > + constexpr unsigned int numUnicamDevices = 2;
> > >
> > > Constants should start with a k prefix, that is kNumUnicamDevices.
> > >
> > > >
> > > > - if (!unicamDevice) {
> > > > - LOG(RPI, Debug) << "Unable to acquire a Unicam
> instance";
> > > > - return false;
> > > > - }
> > > > + /*
> > > > + * Loop over all Unicam instances, but return out once a match
> is found.
> > > > + * This is to ensure we correctly enumrate the camera when an
> instance
> > > > + * of Unicam has registered with media controller, but has not
> registered
> > > > + * device nodes due to a sensor subdevice failure.
> > > > + */
> > > > + for (unsigned int i = 0; i < numUnicamDevices; i++) {
> > > > + DeviceMatch unicam("unicam");
> > > > + MediaDevice *unicamDevice =
> acquireMediaDevice(enumerator, unicam);
> > > >
> > > > - DeviceMatch isp("bcm2835-isp");
> > > > - MediaDevice *ispDevice = acquireMediaDevice(enumerator, isp);
> > > > + if (!unicamDevice) {
> > > > + LOG(RPI, Debug) << "Unable to acquire a Unicam
> instance";
> > > > + continue;
> > >
> > > This looks weird, if the unicam device can't be acquired, I don't see
> > > how the next iteration of the loop could successfully acquire another
> > > instance. I would thus break here.
> >
> > This is probably me not understanding how the media device enumeration
> stuff
> > works, but I thought the continue would be needed for situations where
> we want
> > simultaneous dual cameras running in separate processes. For example,
> process 0
> > acquires "Unicam 0" and starts running as normal. Process 1 starts and
> goes
> > through match() where "Unicam 0" still exists in the entity list, but
> fails to
> > acquire because it is locked by process 0. So we have to move on to
> "Unicam 1"
> > which is acquired correctly for process 1. Is that understanding wrong?
>
> The minimal inter-process locking support in libcamera only operates
> when trying to acquire a *camera* with Camera::acquire(). The
> acquireMediaDevice() function is a bit confusing, its name refers to the
> pipeline handler acquiring a MediaDevice from the DeviceEnumerator,
> guaranteeing that the pipeline handler gets ownership of the media
> device and no other pipeline handler *in the same process* will be able
> to acquire it. Two processes running libcamera will both get "Unicam 0"
> in the first iteration of the loop.
>
For my clarification, so process 1 will still acquire Unicam 0, but when it
comes to camera.start(), will fail since process 0 will have Unicam 0
running in
its process. Is that right?
Naush
> > > > + }
> > > >
> > > > - if (!ispDevice) {
> > > > - LOG(RPI, Debug) << "Unable to acquire ISP instance";
> > > > - return false;
> > > > - }
> > > > + DeviceMatch isp("bcm2835-isp");
> > > > + MediaDevice *ispDevice =
> acquireMediaDevice(enumerator, isp);
> > > >
> > > > - /*
> > > > - * The loop below is used to register multiple cameras behind
> one or more
> > > > - * video mux devices that are attached to a particular Unicam
> instance.
> > > > - * Obviously these cameras cannot be used simultaneously.
> > > > - */
> > > > - unsigned int numCameras = 0;
> > > > - for (MediaEntity *entity : unicamDevice->entities()) {
> > > > - if (entity->function() != MEDIA_ENT_F_CAM_SENSOR)
> > > > + if (!ispDevice) {
> > > > + LOG(RPI, Debug) << "Unable to acquire ISP
> instance";
> > > > continue;
> > >
> > > Shouldn't you release the unicam device in this case ? I think it would
> > > be better to first loop over unicam instances, ignoring any instance
> > > than has no connected camera sensor, and then, if an instance with a
> > > connected sensor is found, acquire an ISP instance.
> >
> > I think we discussed this briefly in the github comments. There is no
> > compliment releaseMediaDevice() call that I can use to release the
> device.
>
> It's an issue indeed. The design idea was to release all acquired media
> devices automatically when the match() function returns false, but that
> doesn't allow releasing media device that have been acquired and turned
> out not to be needed.
>
> In this specific case, if you acquire a unicam instance that has no
> connected sensor, it's fine if it stays acquired as no other pipeline
> handler instance would be able to use it for a meaningful purpose
> anyway, but in general this is something we should probably fix.
>
> > Regarding the second part of the comment, yes, I could move the isp
> acquire bit
> > into the for (unicamDevice->entities()) loop to optimise this a bit.
> >
> > > > + }
> > > >
> > > > - int ret = registerCamera(unicamDevice, ispDevice,
> entity);
> > > > - if (ret)
> > > > - LOG(RPI, Error) << "Failed to register camera "
> > > > - << entity->name() << ": " <<
> ret;
> > > > - else
> > > > - numCameras++;
> > > > + /*
> > > > + * The loop below is used to register multiple cameras
> behind one or more
> > > > + * video mux devices that are attached to a particular
> Unicam instance.
> > > > + * Obviously these cameras cannot be used
> simultaneously.
> > > > + */
> > > > + unsigned int numCameras = 0;
> > > > + for (MediaEntity *entity : unicamDevice->entities()) {
> > > > + if (entity->function() !=
> MEDIA_ENT_F_CAM_SENSOR)
> > > > + continue;
> > > > +
> > > > + int ret = registerCamera(unicamDevice,
> ispDevice, entity);
> > > > + if (ret)
> > > > + LOG(RPI, Error) << "Failed to register
> camera "
> > > > + << entity->name() <<
> ": " << ret;
> > > > + else
> > > > + numCameras++;
> > > > + }
> > > > +
> > > > + if (numCameras)
> > > > + return true;
> > > > }
> > > >
> > > > - return !!numCameras;
> > > > + return false;
> > > > }
> > > >
> > > > void PipelineHandlerRPi::releaseDevice(Camera *camera)
>
> --
> Regards,
>
> Laurent Pinchart
>
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