[libcamera-devel] [PATCH v2] android: Return -EUSERS when failed to open a Camera that's in use

[Paul Elder]

The correct return value for the HAL for hal_dev_open() when trying to
open a camera that's already opened is EUSERS. Make hal_dev_open()
return -EUSERS, and plumb the logic for this through
CameraHalManager::open().

Signed-off-by: Paul Elder <paul.elder at ideasonboard.com>

---
I think the only discussion point that we have so far is whether -EUSERS
should be returned only in HAL, or in libcamera as well, which currently
returners -EBUSY.

Changes in v2:
- use structured binding when opening the camera in hal_dev_open()
- expand the error message
---
 src/android/camera3_hal.cpp        |  9 +++++++--
 src/android/camera_hal_manager.cpp | 15 ++++++++-------
 src/android/camera_hal_manager.h   |  4 +++-
 3 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/src/android/camera3_hal.cpp b/src/android/camera3_hal.cpp
index d6e04af2..7b5f3898 100644
--- a/src/android/camera3_hal.cpp
+++ b/src/android/camera3_hal.cpp
@@ -77,8 +77,13 @@ static int hal_dev_open(const hw_module_t *module, const char *name,
 	LOG(HAL, Debug) << "Open camera " << name;
 
 	int id = atoi(name);
-	CameraDevice *camera = cameraManager.open(id, module);
-	if (!camera) {
+	auto [camera, ret] = cameraManager.open(id, module);
+	if (ret == -EBUSY) {
+		LOG(HAL, Error)
+			<< "Failed to open camera module '" << id
+			<< "', as it is in use";
+		return -EUSERS;
+	} else if (!camera) {
 		LOG(HAL, Error)
 			<< "Failed to open camera module '" << id << "'";
 		return -ENODEV;
diff --git a/src/android/camera_hal_manager.cpp b/src/android/camera_hal_manager.cpp
index 189eda2b..aeff14bd 100644
--- a/src/android/camera_hal_manager.cpp
+++ b/src/android/camera_hal_manager.cpp
@@ -65,28 +65,29 @@ int CameraHalManager::init()
 	return 0;
 }
 
-CameraDevice *CameraHalManager::open(unsigned int id,
-				     const hw_module_t *hardwareModule)
+std::tuple<CameraDevice *, int>
+CameraHalManager::open(unsigned int id, const hw_module_t *hardwareModule)
 {
 	MutexLocker locker(mutex_);
 
 	if (!callbacks_) {
 		LOG(HAL, Error) << "Can't open camera before callbacks are set";
-		return nullptr;
+		return { nullptr, -ENODEV };
 	}
 
 	CameraDevice *camera = cameraDeviceFromHalId(id);
 	if (!camera) {
 		LOG(HAL, Error) << "Invalid camera id '" << id << "'";
-		return nullptr;
+		return { nullptr, -ENODEV };
 	}
 
-	if (camera->open(hardwareModule))
-		return nullptr;
+	int ret = camera->open(hardwareModule);
+	if (ret)
+		return { nullptr, ret };
 
 	LOG(HAL, Info) << "Open camera '" << id << "'";
 
-	return camera;
+	return { camera, 0 };
 }
 
 void CameraHalManager::cameraAdded(std::shared_ptr<Camera> cam)
diff --git a/src/android/camera_hal_manager.h b/src/android/camera_hal_manager.h
index a91decc7..24bf716c 100644
--- a/src/android/camera_hal_manager.h
+++ b/src/android/camera_hal_manager.h
@@ -10,6 +10,7 @@
 #include <map>
 #include <mutex>
 #include <stddef.h>
+#include <tuple>
 #include <vector>
 
 #include <hardware/camera_common.h>
@@ -28,7 +29,8 @@ public:
 
 	int init();
 
-	CameraDevice *open(unsigned int id, const hw_module_t *module);
+	std::tuple<CameraDevice *, int>
+	open(unsigned int id, const hw_module_t *module);
 
 	unsigned int numCameras() const;
 	int getCameraInfo(unsigned int id, struct camera_info *info);
-- 
2.27.0