[libcamera-devel] [PATCH LIBCAMERA v5] libcamera: utils: adapt libcameraPath to match use cases

[Kaaira Gupta]

The two callers of functions libcameraPath() and isLibcameraInstalled()
end up using the same process and finally use the path with
libcamera.so. Hence write a function libcameraBuildPath() which
combines their functions and returns the root of the build sources
when the library has not been installed, but is running from the build
tree, thereby making call sites simpler.

When the library is installed, libcameraBuildPath() will return an empty
string.

Make changes in the call sites accordingly.

Signed-off-by: Kaaira Gupta <kgupta at es.iitr.ac.in>
---
Changes since v4:
	- Updated documentation of libcameraBuildPath() 

Changes since v3:
        - removed isLibcameraInstalled() from utils.h
        - reformatted the code to reduce indentation of the code that
          implements actual logic, also, to catch the errors
          immediately.
        - changes in spellings and whitespaces in commit messages.

Changes since v2:
        - rename subject line and add necessary details in commit
          message.
        - Solve whitespace issues.
        - specify the final 'slash' for directory path in return
          statement itself.

Changes since v1:
        - rename function to libcameraBuildPath() instead, and return
          the root of libcamera source, and not the source directory
          root.
        - Return empty string instead of nullptr when ret==0

 src/libcamera/include/utils.h |  4 +---
 src/libcamera/ipa_manager.cpp |  5 +++--
 src/libcamera/ipa_proxy.cpp   |  6 +++---
 src/libcamera/utils.cpp       | 26 ++++++++++++++++++--------
 4 files changed, 25 insertions(+), 16 deletions(-)

diff --git a/src/libcamera/include/utils.h b/src/libcamera/include/utils.h
index bc96e79..cfa620f 100644
--- a/src/libcamera/include/utils.h
+++ b/src/libcamera/include/utils.h
@@ -143,9 +143,7 @@ private:
 
 details::StringSplitter split(const std::string &str, const std::string &delim);
 
-bool isLibcameraInstalled();
-
-std::string libcameraPath();
+std::string libcameraBuildPath();
 
 } /* namespace utils */
 
diff --git a/src/libcamera/ipa_manager.cpp b/src/libcamera/ipa_manager.cpp
index 0bd280c..bcaae35 100644
--- a/src/libcamera/ipa_manager.cpp
+++ b/src/libcamera/ipa_manager.cpp
@@ -119,8 +119,9 @@ IPAManager::IPAManager()
 	 * path for the IPA from that point. We need to recurse one level of
 	 * sub-directories to match the build tree.
 	 */
-	if (!utils::isLibcameraInstalled()) {
-		std::string ipaBuildPath = utils::dirname(utils::libcameraPath()) + "/../ipa";
+	std::string root = utils::libcameraBuildPath();
+	if (!root.empty()) {
+		std::string ipaBuildPath = root + "src/ipa";
 		constexpr int maxDepth = 1;
 
 		LOG(IPAManager, Info)
diff --git a/src/libcamera/ipa_proxy.cpp b/src/libcamera/ipa_proxy.cpp
index 2f866cc..5fd88a4 100644
--- a/src/libcamera/ipa_proxy.cpp
+++ b/src/libcamera/ipa_proxy.cpp
@@ -97,9 +97,9 @@ std::string IPAProxy::resolvePath(const std::string &file) const
 	 * This requires identifying the path of the libcamera.so, and
 	 * referencing a relative path for the proxy workers from that point.
 	 */
-	if (!utils::isLibcameraInstalled()) {
-		std::string ipaProxyDir = utils::dirname(utils::libcameraPath())
-					  + "/proxy/worker";
+	std::string root = utils::libcameraBuildPath();
+	if (!root.empty()) {
+		std::string ipaProxyDir = root + "src/libcamera/proxy/worker";
 
 		LOG(IPAProxy, Info)
 			<< "libcamera is not installed. Loading proxy workers from'"
diff --git a/src/libcamera/utils.cpp b/src/libcamera/utils.cpp
index 7e118fa..58ee7cc 100644
--- a/src/libcamera/utils.cpp
+++ b/src/libcamera/utils.cpp
@@ -340,23 +340,33 @@ bool isLibcameraInstalled()
 }
 
 /**
- * \brief Identify the libcamera.so path
+ * \brief Retrieve the path to the build directory
  *
- * This function locates the running libcamera.so and returns its full path,
- * including the file name.
+ * During development, it is useful to run libcamera binaries directly from the
+ * build directory without installing them. This function helps components that
+ * need to locate resources, such as IPA modules or IPA proxy workers, by
+ * providing them with the path to the root of the build directory. Callers can
+ * then use it to complement or override searches in system-wide directories.
  *
- * \return A string stating the path
+ * If libcamera has been installed, the build directory path is not available
+ * and this function returns an empty string.
+ *
+ * \return The path to the build directory if running from a build, or an empty
+ * string otherwise
  */
-std::string libcameraPath()
+std::string libcameraBuildPath()
 {
+	if (isLibcameraInstalled())
+		return std::string();
+
 	Dl_info info;
 
 	/* Look up our own symbol. */
-	int ret = dladdr(reinterpret_cast<void *>(libcameraPath), &info);
+	int ret = dladdr(reinterpret_cast<void *>(libcameraBuildPath), &info);
 	if (ret == 0)
-		return nullptr;
+		return std::string();
 
-	return info.dli_fname;
+	return dirname(info.dli_fname) + "/../../";
 }
 
 } /* namespace utils */
-- 
2.17.1