android: Allow to override config file path from env

The HAL config file is assumed to be in the LIBCAMERA_SYSCONF_DIR
directory, which is defined by the meson build system at compile time.

As the filesystem layout on Android installations might be device/build
specific, allow to override such assumption using the
LIBCAMERA_HAL_CONFIG_PATH environment variable and document its usage.

While at it, remove quotes from the error message, as the file path
doesn't contain any space.

Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>

2 files changed, 25 insertions, 2 deletions

diff --git a/Documentation/environment_variables.rst b/Documentation/environment_variables.rst
index f092cbbd..ef2794f0 100644
--- a/Documentation/environment_variables.rst
+++ b/Documentation/environment_variables.rst
@@ -37,6 +37,12 @@ LIBCAMERA_IPA_MODULE_PATH
 
    Example value: ``${HOME}/.libcamera/lib:/opt/libcamera/vendor/lib``
 
+LIBCAMERA_HAL_CONFIG_PATH
+   Define custom search location for the Android HAL config file
+   ``camera_hal.yaml`` (`more <HAL config_>`__).
+
+   Example value: ``/system/etc/libcamera``, ``/vendor/etc/libcamera``
+
 Further details
 ---------------
 
@@ -149,3 +155,15 @@ operation are the installed system path (for example on Debian:
 ``/usr/local/x86_64-pc-linux-gnu/libcamera``) and the build directory.
 With the ``LIBCAMERA_IPA_MODULE_PATH``, you can specify a non-default location
 to search for IPA modules.
+
+HAL config
+~~~~~~~~~~
+
+The Android camera HAL requires a configuration file where all built-in cameras
+and their properties are enumerated (pluggable cameras, such as UVC cameras do
+not need to be described there). The HAL configuration file has to be named
+`camera_hal.yaml` and its default location is ``LIBCAMERA_SYSCONF_DIR`` which
+can be overridden by using the ``LIBCAMERA_HAL_CONFIG_PATH`` environment
+variable.
+
+`Examples <https://git.libcamera.org/libcamera/libcamera.git/tree/src/android/data>`__
diff --git a/src/android/camera_hal_config.cpp b/src/android/camera_hal_config.cpp
index 0e7cde63..0942263c 100644
--- a/src/android/camera_hal_config.cpp
+++ b/src/android/camera_hal_config.cpp
@@ -11,6 +11,7 @@
 
 #include <libcamera/base/file.h>
 #include <libcamera/base/log.h>
+#include <libcamera/base/utils.h>
 
 #include "libcamera/internal/yaml_parser.h"
 
@@ -159,12 +160,16 @@ CameraHalConfig::CameraHalConfig()
  */
 int CameraHalConfig::parseConfigurationFile()
 {
-	std::string filePath = LIBCAMERA_SYSCONF_DIR "/camera_hal.yaml";
+	const char *configPath = utils::secure_getenv("LIBCAMERA_HAL_CONFIG_PATH");
+	if (!configPath)
+		configPath = LIBCAMERA_SYSCONF_DIR;
+	std::string filePath(configPath);
+	filePath += "/camera_hal.yaml";
 
 	File file(filePath);
 	if (!file.exists()) {
 		LOG(HALConfig, Debug)
-			<< "Configuration file: \"" << filePath << "\" not found";
+			<< "Configuration file " << filePath << " not found";
 		return -ENOENT;
 	}