[libcamera-devel] [PATCH v3 08/11] libcamera: camera: Extend with a Stopping state

[Kieran Bingham]

Hi Laurent,

On 26/03/2021 02:36, Laurent Pinchart wrote:
> Hi Kieran,
> 
> Thank you for the patch.
> 
> On Thu, Mar 25, 2021 at 01:42:28PM +0000, Kieran Bingham wrote:
>> When the camera is being stop()ped, active requests will complete. These
>> may trigger an application to re-queue those requests to the camera but
>> that is not permitted.
> 
> Maybe ", and is an error in the application." to be clear ?

Yes,

> 
>>
>> Extend the camera state to include a stopping state which is entered as
>> soon as a call to stop() is made. At this point, any request queued will
>> be rejected with a warning, while any pending requests are either
>> successfully completed or cancelled.
> 
> Should it be an error instead of a warning ?

The warning will come from the isAccessAllowed log level.

I don't want to duplicate an error message, but it would probably be
considered an error.

We could try to pass in a log level to the isAccessAllowed, but I think
we're overloading those operators enough already ...

Perhaps we could actually raise the log from isAccessAllowed further
from Debug to Warning, to all the way to Error?

If an operation is made in the wrong state - it's an error isn't it ?


> 
>> When the pipeline handler has finished stopping, the camera state will
>> transition to the CameraConfigured state where it can begin to accept
>> requests again, and be restarted.
>>
>> Signed-off-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
>> ---
>>  src/libcamera/camera.cpp | 18 ++++++++++++++++--
>>  1 file changed, 16 insertions(+), 2 deletions(-)
>>
>> diff --git a/src/libcamera/camera.cpp b/src/libcamera/camera.cpp
>> index 336ab8695ab3..7f7956ba732f 100644
>> --- a/src/libcamera/camera.cpp
>> +++ b/src/libcamera/camera.cpp
>> @@ -339,6 +339,7 @@ public:
>>  		CameraAvailable,
>>  		CameraAcquired,
>>  		CameraConfigured,
>> +		CameraStopping,
>>  		CameraRunning,
>>  	};
>>  
>> @@ -382,6 +383,7 @@ static const char *const camera_state_names[] = {
>>  	"Available",
>>  	"Acquired",
>>  	"Configured",
>> +	"Stopping",
>>  	"Running",
>>  };
>>  
>> @@ -492,6 +494,7 @@ void Camera::Private::setState(State state)
>>   *   node [shape = doublecircle ]; Available;
>>   *   node [shape = circle ]; Acquired;
>>   *   node [shape = circle ]; Configured;
>> + *   node [shape = circle ]; Stopping;
>>   *   node [shape = circle ]; Running;
>>   *
>>   *   Available -> Available [label = "release()"];
>> @@ -504,7 +507,8 @@ void Camera::Private::setState(State state)
>>   *   Configured -> Configured [label = "configure(), createRequest()"];
>>   *   Configured -> Running [label = "start()"];
>>   *
>> - *   Running -> Configured [label = "stop()"];
>> + *   Running -> Stopping [label = "stop()"];
>> + *   Stopping -> Configured;
>>   *   Running -> Running [label = "createRequest(), queueRequest()"];
>>   * }
>>   * \enddot
>> @@ -524,6 +528,12 @@ void Camera::Private::setState(State state)
>>   * release() the camera and to get back to the Available state or start()
>>   * it to progress to the Running state.
>>   *
>> + * \subsubsection Stopping
>> + * The camera has been asked to stop. Pending reqeusts are being completed or
> 
> s/reqeusts/requests/

Fixed, thanks.


> 
> Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> 
>> + * cancelled, and no new requests are permitted to be queued. The camera will
>> + * transition to the Configured state when all queued requests have been
>> + * returned to the application.
>> + *
>>   * \subsubsection Running
>>   * The camera is running and ready to process requests queued by the
>>   * application. The camera remains in this state until it is stopped and moved
>> @@ -1071,6 +1081,8 @@ int Camera::stop()
>>  
>>  	LOG(Camera, Debug) << "Stopping capture";
>>  
>> +	d->setState(Private::CameraStopping);
>> +
>>  	d->pipe_->invokeMethod(&PipelineHandler::stop, ConnectionTypeBlocking,
>>  			       this);
>>  
>> @@ -1091,7 +1103,9 @@ void Camera::requestComplete(Request *request)
>>  	Private *const d = LIBCAMERA_D_PTR();
>>  
>>  	/* Disconnected cameras are still able to complete requests. */
>> -	int ret = d->isAccessAllowed(__FUNCTION__, Private::CameraRunning);
>> +	int ret = d->isAccessAllowed(__FUNCTION__,
>> +				     Private::CameraStopping,
>> +				     Private::CameraRunning);
>>  	if (ret < 0 && ret != -ENODEV)
>>  		LOG(Camera, Fatal) << "Trying to complete a request when stopped";
>>  
> 

-- 
Regards
--
Kieran