[libcamera-devel] [PATCH 5/8] libcamera: camera: add state machine to control access from applications
Niklas Söderlund
niklas.soderlund at ragnatech.se
Tue Feb 26 03:18:54 CET 2019
There is a need to better control the order of operations an application
perform on a camera for it to function correctly. Add a basic state
machine to ensure applications perform operations on the camera in good
order.
Internal to the Camera four states are added; Disconnected, Free,
Acquired and Running. Each state represents a higher state of
configuration of the camera ultimately leading to the highest state
where the camera is capturing frames. Each state supports a subset of
operations the application can perform.
* Disconnected
Is the lowest state a camera can be in. It indicates that the camera
have been disconnected from the system and the only operations an
application shall do at this point is clean up and release the camera so
it can be removed from libcamera as well.
* Free
Is the base state of a camera, an application can inspect the properties
of the camera to determine if it wish to use it or not. If an
application wish to use a camera it should acquire it to proceed to the
next state.
* Acquired
When an application have acquired a camera it have exclusive access to
it and can modify the cameras parameters to prepare it for capturing.
Once the application is done configure the camera it may be started to
progress to the running state. Once the camera is started it can not be
reconfigured until it's stopped.
* Running
In this state the camera is running and able to process requests queued
to it by the application. Once an application finish capturing the
camera shall be stopped to change the state to acquired where it can be
reconfigured or released.
Signed-off-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>
---
include/libcamera/camera.h | 14 ++++-
src/libcamera/camera.cpp | 110 +++++++++++++++++++++++--------------
2 files changed, 80 insertions(+), 44 deletions(-)
diff --git a/include/libcamera/camera.h b/include/libcamera/camera.h
index bf70255a6a5ea364..8c8545b074e8ae13 100644
--- a/include/libcamera/camera.h
+++ b/include/libcamera/camera.h
@@ -55,20 +55,28 @@ public:
int stop();
private:
+ enum State {
+ Disconnected,
+ Free,
+ Acquired,
+ Running,
+ };
+
Camera(PipelineHandler *pipe, const std::string &name);
~Camera();
+ bool stateIs(State state) const;
+ bool stateIsAtleast(State state) const;
+
friend class PipelineHandler;
void disconnect();
- int exclusiveAccess();
std::shared_ptr<PipelineHandler> pipe_;
std::string name_;
std::vector<Stream *> streams_;
std::vector<Stream *> activeStreams_;
- bool acquired_;
- bool disconnected_;
+ State state_;
};
} /* namespace libcamera */
diff --git a/src/libcamera/camera.cpp b/src/libcamera/camera.cpp
index d4258fe3c7551af3..c50b14bbd904fc1c 100644
--- a/src/libcamera/camera.cpp
+++ b/src/libcamera/camera.cpp
@@ -116,17 +116,47 @@ const std::string &Camera::name() const
*/
Camera::Camera(PipelineHandler *pipe, const std::string &name)
- : pipe_(pipe->shared_from_this()), name_(name), acquired_(false),
- disconnected_(false)
+ : pipe_(pipe->shared_from_this()), name_(name), state_(Free)
{
}
Camera::~Camera()
{
- if (acquired_)
+ if (state_ > Free)
LOG(Camera, Error) << "Removing camera while still in use";
}
+static const std::string stateNames[] = {
+ "Disconnected",
+ "Free",
+ "Acquired",
+ "Running",
+};
+
+bool Camera::stateIs(State state) const
+{
+ if (state_ == state)
+ return true;
+
+ LOG(Camera, Error) << "Camera in " << stateNames[state_]
+ << " state trying operation requiering "
+ << stateNames[state] << " state";
+
+ return false;
+}
+
+bool Camera::stateIsAtleast(State state) const
+{
+ if (state_ >= state)
+ return true;
+
+ LOG(Camera, Error) << "Camera in " << stateNames[state_]
+ << " state trying operation requiering at least "
+ << stateNames[state] << " state";
+
+ return false;
+}
+
/**
* \brief Notify camera disconnection
*
@@ -140,7 +170,7 @@ void Camera::disconnect()
{
LOG(Camera, Debug) << "Disconnecting camera " << name_;
- disconnected_ = true;
+ state_ = Disconnected;
disconnected.emit(this);
}
@@ -162,10 +192,11 @@ void Camera::disconnect()
*/
int Camera::acquire()
{
- if (acquired_)
+ if (!stateIs(Free))
return -EBUSY;
- acquired_ = true;
+ state_ = Acquired;
+
return 0;
}
@@ -177,7 +208,10 @@ int Camera::acquire()
*/
void Camera::release()
{
- acquired_ = false;
+ if (!stateIs(Acquired))
+ return;
+
+ state_ = Free;
}
/**
@@ -191,6 +225,9 @@ void Camera::release()
*/
const std::vector<Stream *> &Camera::streams() const
{
+ if (!stateIsAtleast(Free))
+ std::vector<Stream *>{};
+
return streams_;
}
@@ -213,7 +250,7 @@ const std::vector<Stream *> &Camera::streams() const
std::map<Stream *, StreamConfiguration>
Camera::streamConfiguration(std::vector<Stream *> &streams)
{
- if (disconnected_ || !streams.size())
+ if (!stateIsAtleast(Free) || !streams.size())
return std::map<Stream *, StreamConfiguration>{};
return pipe_->streamConfiguration(this, streams);
@@ -244,9 +281,8 @@ int Camera::configureStreams(std::map<Stream *, StreamConfiguration> &config)
{
int ret;
- ret = exclusiveAccess();
- if (ret)
- return ret;
+ if (!stateIs(Acquired))
+ return -EACCES;
if (!config.size()) {
LOG(Camera, Error)
@@ -284,11 +320,8 @@ int Camera::configureStreams(std::map<Stream *, StreamConfiguration> &config)
*/
int Camera::allocateBuffers()
{
- int ret;
-
- ret = exclusiveAccess();
- if (ret)
- return ret;
+ if (!stateIs(Acquired))
+ return -EACCES;
if (activeStreams_.empty()) {
LOG(Camera, Error)
@@ -297,7 +330,7 @@ int Camera::allocateBuffers()
}
for (Stream *stream : activeStreams_) {
- ret = pipe_->allocateBuffers(this, stream);
+ int ret = pipe_->allocateBuffers(this, stream);
if (ret) {
LOG(Camera, Error) << "Failed to allocate buffers";
freeBuffers();
@@ -313,6 +346,9 @@ int Camera::allocateBuffers()
*/
void Camera::freeBuffers()
{
+ if (!stateIs(Acquired))
+ return;
+
for (Stream *stream : activeStreams_) {
if (!stream->bufferPool().count())
continue;
@@ -336,7 +372,7 @@ void Camera::freeBuffers()
*/
Request *Camera::createRequest()
{
- if (exclusiveAccess())
+ if (!stateIsAtleast(Acquired))
return nullptr;
return new Request(this);
@@ -358,13 +394,10 @@ Request *Camera::createRequest()
*/
int Camera::queueRequest(Request *request)
{
- int ret;
+ if (!stateIs(Running))
+ return -EACCES;
- ret = exclusiveAccess();
- if (ret)
- return ret;
-
- ret = request->prepare();
+ int ret = request->prepare();
if (ret) {
LOG(Camera, Error) << "Failed to prepare request";
return ret;
@@ -385,13 +418,18 @@ int Camera::queueRequest(Request *request)
*/
int Camera::start()
{
- int ret = exclusiveAccess();
- if (ret)
- return ret;
+ if (!stateIs(Acquired))
+ return -EACCES;
LOG(Camera, Debug) << "Starting capture";
- return pipe_->start(this);
+ int ret = pipe_->start(this);
+ if (ret)
+ return ret;
+
+ state_ = Running;
+
+ return 0;
}
/**
@@ -405,24 +443,14 @@ int Camera::start()
*/
int Camera::stop()
{
- int ret = exclusiveAccess();
- if (ret)
- return ret;
+ if (!stateIs(Running))
+ return -EACCES;
LOG(Camera, Debug) << "Stopping capture";
pipe_->stop(this);
- return 0;
-}
-
-int Camera::exclusiveAccess()
-{
- if (disconnected_)
- return -ENODEV;
-
- if (!acquired_)
- return -EACCES;
+ state_ = Acquired;
return 0;
}
--
2.20.1
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