android: Return -EUSERS when failed to open a Camera that's in use

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().

This allows the following CTS tests to pass:
- android.hardware.camera2.cts.CameraManagerTest#testCameraManagerOpenAllCameras
- android.hardware.camera2.cts.MultiViewTest#testDualCameraPreview

Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Hirokazu Honda <hiroh@chromium.org>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>

src/android/camera3_hal.cpp

@@ -77,11 +77,11 @@ 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);
+	auto [camera, ret] = cameraManager.open(id, module);
 	if (!camera) {
 		LOG(HAL, Error)
 			<< "Failed to open camera module '" << id << "'";
-		return -ENODEV;
+		return ret == -EBUSY ? -EUSERS : ret;
 	}
 
 	*device = &camera->camera3Device()->common;

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)

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);