[libcamera-devel] [PATCH v4 3/6] libcamera: device_enumerator: Emit a signal when a new devices are added

[Kieran Bingham]

Hi Umang,

On 12/06/2020 11:45, Laurent Pinchart wrote:
> Hi Umang,
> 
> Thank you for the patch.
> 
> On Thu, Jun 11, 2020 at 05:16:05PM +0000, Umang Jain wrote:
>> Emit a signal whenever a new MediaDevices are added to the
> 
> s/a new/new/
> 
>> DeviceEnumerator. This will allow CameraManager to be notified
>> about the new devices and it can re-emumerate all the devices
>> currently present on the system.
>>
>> Device enumeration by the CameraManger is a expensive operation hence,

I'd ignore this generally, but as you are already likely to update the
commit message from above:

s/is a/is an/


>> we want one signal emission per 'x' milliseconds to notify multiple
>> devices additions as a single batch, by the DeviceEnumerator.
>> Add a \todo to investigate the support for that.
>>
>> Signed-off-by: Umang Jain <email at uajain.com>
>> Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
>> ---
>>  include/libcamera/internal/device_enumerator.h |  4 ++++
>>  src/libcamera/camera_manager.cpp               |  4 ++--
>>  src/libcamera/device_enumerator.cpp            | 13 +++++++++++++
>>  3 files changed, 19 insertions(+), 2 deletions(-)
>>
>> diff --git a/include/libcamera/internal/device_enumerator.h b/include/libcamera/internal/device_enumerator.h
>> index 25a3630..a985040 100644
>> --- a/include/libcamera/internal/device_enumerator.h
>> +++ b/include/libcamera/internal/device_enumerator.h
>> @@ -13,6 +13,8 @@
>>  
>>  #include <linux/media.h>
>>  
>> +#include <libcamera/signal.h>
>> +
>>  namespace libcamera {
>>  
>>  class MediaDevice;
>> @@ -43,6 +45,8 @@ public:
>>  
>>  	std::shared_ptr<MediaDevice> search(const DeviceMatch &dm);
>>  
>> +	Signal<> devicesAdded;
>> +
>>  protected:
>>  	std::unique_ptr<MediaDevice> createDevice(const std::string &deviceNode);
>>  	void addDevice(std::unique_ptr<MediaDevice> &&media);
>> diff --git a/src/libcamera/camera_manager.cpp b/src/libcamera/camera_manager.cpp
>> index aba5a0c..17a4afb 100644
>> --- a/src/libcamera/camera_manager.cpp
>> +++ b/src/libcamera/camera_manager.cpp
>> @@ -155,12 +155,12 @@ void CameraManager::Private::createPipelineHandlers()
>>  		}
>>  	}
>>  
>> -	/* \todo Register hot-plug callback here */
>> +	enumerator_->devicesAdded.connect(this, &Private::createPipelineHandlers);
>>  }
>>  
>>  void CameraManager::Private::cleanup()
>>  {
>> -	/* \todo Unregister hot-plug callback here */
>> +	enumerator_->devicesAdded.disconnect(this, &Private::createPipelineHandlers);
>>  
>>  	/*
>>  	 * Release all references to cameras and pipeline handlers to ensure
>> diff --git a/src/libcamera/device_enumerator.cpp b/src/libcamera/device_enumerator.cpp
>> index e21a2a7..e3264a5 100644
>> --- a/src/libcamera/device_enumerator.cpp
>> +++ b/src/libcamera/device_enumerator.cpp
>> @@ -227,6 +227,16 @@ std::unique_ptr<MediaDevice> DeviceEnumerator::createDevice(const std::string &d
>>  	return media;
>>  }
>>  
>> +/**
>> +* \var DeviceEnumerator::devicesAdded
>> +* \brief Notify of new media devices being found
>> +*
>> +* This signal is emitted when the device enumerator finds new media devices in
>> +* the system. It may be emitted for every newly detected device, or once for
>> +* multiple of devices, at the discretion of the device enumerator. Not all

's/ of //'
== "or once for multiple devices"

Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>


>> +* device enumerator types may support dynamic detection of new devices.
>> +*/
>> +
>>  /**
>>   * \brief Add a media device to the enumerator
>>   * \param[in] media media device instance to add
>> @@ -242,6 +252,9 @@ void DeviceEnumerator::addDevice(std::unique_ptr<MediaDevice> &&media)
>>  		<< "Added device " << media->deviceNode() << ": " << media->driver();
>>  
>>  	devices_.push_back(std::move(media));
>> +
>> +	/* \todo To batch multiple additions, emit with a small delay here. */
>> +	devicesAdded.emit();
>>  }
>>  
>>  /**
> 

-- 
Regards
--
Kieran