libcamera: process: start(): Use span instead of vector

Use a span instead of a const reference to a vector, this does not
change the behaviour and allows e.g. arrays to be used to hold
arguments/file descriptors.

Signed-off-by: Barnabás Pőcze <barnabas.pocze@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

src/libcamera/ipc_pipe_unixsocket.cpp

@@ -28,10 +28,6 @@ IPCPipeUnixSocket::IPCPipeUnixSocket(const char *ipaModulePath,
 				     const char *ipaProxyWorkerPath)
 	: IPCPipe()
 {
-	std::vector<int> fds;
-	std::vector<std::string> args;
-	args.push_back(ipaModulePath);
-
 	socket_ = std::make_unique<IPCUnixSocket>();
 	UniqueFD fd = socket_->create();
 	if (!fd.isValid()) {
@@ -39,8 +35,9 @@ IPCPipeUnixSocket::IPCPipeUnixSocket(const char *ipaModulePath,
 		return;
 	}
 	socket_->readyRead.connect(this, &IPCPipeUnixSocket::readyRead);
-	args.push_back(std::to_string(fd.get()));
-	fds.push_back(fd.get());
+
+	std::array args{ std::string(ipaModulePath), std::to_string(fd.get()) };
+	std::array fds{ fd.get() };
 
 	proc_ = std::make_unique<Process>();
 	int ret = proc_->start(ipaProxyWorkerPath, args, fds);

src/libcamera/process.cpp

@@ -235,8 +235,8 @@ Process::~Process()
  * or a negative error code otherwise
  */
 int Process::start(const std::string &path,
-		   const std::vector<std::string> &args,
-		   const std::vector<int> &fds)
+		   Span<const std::string> args,
+		   Span<const int> fds)
 {
 	int ret;
 
@@ -262,7 +262,7 @@ int Process::start(const std::string &path,
 		if (isolate())
 			_exit(EXIT_FAILURE);
 
-		std::vector<int> v(fds);
+		std::vector<int> v(fds.begin(), fds.end());
 		v.push_back(STDERR_FILENO);
 		closeAllFdsExcept(v);