[libcamera-devel] [PATCH v2 01/10] libcamera: request: Add support for error flags

[Jacopo Mondi]

From: Paul Elder <paul.elder at ideasonboard.com>

Add error flags to the Request to indicate non-fatal errors.

Applications should check the error() state of the Request to determine
if any fault occurred while processing the request.

Initially, a single error flag ControlError is added to allow a pipeline
handler to report a failure to set controls on a hardware device while
processing the request.

ControlError occurs when a Request was asked to set a control and the
pipeline handler attempted to do so, but it was rejected by the kernel.

Signed-off-by: Paul Elder <paul.elder at ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
Signed-off-by: Jacopo Mondi <jacopo at jmondi.org>
---
 include/libcamera/internal/request.h |  4 ++
 include/libcamera/request.h          |  9 ++++
 src/libcamera/request.cpp            | 72 ++++++++++++++++++++++++++--
 3 files changed, 81 insertions(+), 4 deletions(-)

diff --git a/include/libcamera/internal/request.h b/include/libcamera/internal/request.h
index 9dadd6c60361..76cc32f73f9c 100644
--- a/include/libcamera/internal/request.h
+++ b/include/libcamera/internal/request.h
@@ -42,6 +42,8 @@ public:
 	void prepare(std::chrono::milliseconds timeout = 0ms);
 	Signal<> prepared;
 
+	void setError(Errors error);
+
 private:
 	friend class PipelineHandler;
 	friend std::ostream &operator<<(std::ostream &out, const Request &r);
@@ -59,6 +61,8 @@ private:
 	std::unordered_set<FrameBuffer *> pending_;
 	std::map<FrameBuffer *, std::unique_ptr<EventNotifier>> notifiers_;
 	std::unique_ptr<Timer> timer_;
+
+	Errors errors_;
 };
 
 } /* namespace libcamera */
diff --git a/include/libcamera/request.h b/include/libcamera/request.h
index dffde1536cad..3304da31200d 100644
--- a/include/libcamera/request.h
+++ b/include/libcamera/request.h
@@ -15,6 +15,7 @@
 #include <unordered_set>
 
 #include <libcamera/base/class.h>
+#include <libcamera/base/flags.h>
 #include <libcamera/base/signal.h>
 
 #include <libcamera/controls.h>
@@ -43,6 +44,13 @@ public:
 		ReuseBuffers = (1 << 0),
 	};
 
+	enum ErrorFlag {
+		NoError = 0,
+		ControlError = (1 << 0),
+	};
+
+	using Errors = Flags<ErrorFlag>;
+
 	using BufferMap = std::map<const Stream *, FrameBuffer *>;
 
 	Request(Camera *camera, uint64_t cookie = 0);
@@ -60,6 +68,7 @@ public:
 	uint32_t sequence() const;
 	uint64_t cookie() const { return cookie_; }
 	Status status() const { return status_; }
+	Errors error() const;
 
 	bool hasPendingBuffers() const;
 
diff --git a/src/libcamera/request.cpp b/src/libcamera/request.cpp
index d2af1d2212ad..9a808f19fc03 100644
--- a/src/libcamera/request.cpp
+++ b/src/libcamera/request.cpp
@@ -162,6 +162,7 @@ void Request::Private::cancel()
  */
 void Request::Private::reuse()
 {
+	errors_ = Request::NoError;
 	sequence_ = 0;
 	cancelled_ = false;
 	prepared_ = false;
@@ -284,6 +285,21 @@ void Request::Private::notifierActivated(FrameBuffer *buffer)
 	emitPrepareCompleted();
 }
 
+/**
+ * \brief Update the error flags of the Request
+ * \param[in] error Error flags to apply on the Request
+ *
+ * Flag \a error in the Request which will get reported to the application when
+ * the Request completes.
+ *
+ * Setting an error flag does not cause a Request to fail, and once set it can
+ * only be cleared by the application destroying the Request or calling reuse().
+ */
+void Request::Private::setError(Errors error)
+{
+	errors_ |= error;
+}
+
 void Request::Private::timeout()
 {
 	/* A timeout can only happen if there are fences not yet signalled. */
@@ -318,6 +334,25 @@ void Request::Private::timeout()
  * Reuse the buffers that were previously added by addBuffer()
  */
 
+/**
+ * \enum Request::ErrorFlag
+ * Flags to report errors on a completed request
+ *
+ * \var Request::NoError
+ * No error. The Request completed succesfully and all its buffer contain
+ * valid data
+ *
+ * \var Request::ControlError
+ * Control Error. At least one control was not applied correctly to the camera.
+ * The application should compare the metadata to the requested control values
+ * to check which controls weren't applied.
+ */
+
+/**
+ * \typedef Request::Errors
+ * The error state of the request defined by \a Request::ErrorFlag
+ */
+
 /**
  * \typedef Request::BufferMap
  * \brief A map of Stream to FrameBuffer pointers
@@ -552,14 +587,43 @@ uint32_t Request::sequence() const
  * \brief Retrieve the request completion status
  *
  * The request status indicates whether the request has completed successfully
- * or with an error. When requests are created and before they complete the
- * request status is set to RequestPending, and is updated at completion time
- * to RequestComplete. If a request is cancelled at capture stop before it has
- * completed, its status is set to RequestCancelled.
+ * or has been cancelled before being processed.
+ *
+ * Requests are created with their status set to RequestPending. When
+ * a Request is successfully processed and completed by the Camera its
+ * status is set to RequestComplete. If a Request is cancelled before
+ * being processed, for example because the Camera has been stopped
+ * before the request is completed, its status is set to RequestCancelled.
+ *
+ * Successfully completed requests can complete with errors. Applications shall
+ * inspect the error mask returned by Request::error() before accessing buffers
+ * and data associated with a completed request.
  *
  * \return The request completion status
  */
 
+/**
+ * \brief Retrieve the mask of error flags associated with a completed request
+ *
+ * The request could complete with errors, which indicate failures in
+ * completing correctly parts of the request submitted by the application.
+ *
+ * The possible failure reasons are defined by the error flags defined
+ * by Request::ErrorFlag and application are expected to retrieve the
+ * mask of error flags by using this function before accessing the
+ * buffers and data associated with a completed request.
+ *
+ * Error conditions reported through this function do not change the
+ * request completion status retrieved through Request::status() which
+ * indicates if the Request has been processed or not.
+ *
+ * \return A mask of error identifier with which the request was completed
+ */
+Request::Errors Request::error() const
+{
+	return _d()->errors_;
+}
+
 /**
  * \brief Check if a request has buffers yet to be completed
  *
-- 
2.37.1