builder: honor caller-supplied cross toolchain and PKG_CONFIG

builder/frameworks/arduino.py

@@ -37,9 +37,13 @@ def _overlay_current(d):
         os.symlink(join(_API_DIR, name), join(API_DIR, name))
 
 # Detect libgpiod via pkg-config; fall back gracefully if pkg-config is absent.
+# Honor a caller-supplied $PKG_CONFIG so cross builds resolve libgpiod against
+# the target sysroot rather than the build host (otherwise the simulated GPIO/I2C
+# drivers get compiled in and the daemon can't drive real hardware).
+_pkg_config = os.environ.get("PKG_CONFIG", "pkg-config")
 try:
     has_libgpiod = subprocess.call(
-        ["pkg-config", "--exists", "libgpiod"],
+        [_pkg_config, "--exists", "libgpiod"],
         stdout=subprocess.DEVNULL,
         stderr=subprocess.DEVNULL,
     ) == 0
@@ -57,7 +61,7 @@ def _overlay_current(d):
 
 if has_libgpiod:
     cppdefines.append("ARDULINUX_HARDWARE")
-    raw = subprocess.check_output(["pkg-config", "--cflags", "libgpiod"]).decode().split()
+    raw = subprocess.check_output([_pkg_config, "--cflags", "libgpiod"]).decode().split()
     cpppath += [f[2:] for f in raw if f.startswith("-I")]
 
 env.Append(CPPPATH=cpppath, CPPDEFINES=cppdefines)

builder/main.py

@@ -1,8 +1,28 @@
+import os
 from os.path import basename, join
 from SCons.Script import AlwaysBuild, Default, DefaultEnvironment
 
 env = DefaultEnvironment()
 
+# Honor a caller-supplied cross toolchain from the environment so ArduLinux can
+# be built by external build systems (OpenWRT/buildroot, Yocto, Debian rules)
+# that provide their own compiler and sysroot.  This runs before the framework
+# script (main.py -> BuildProgram -> ProcessProgramDeps -> BuildFrameworks ->
+# arduino.py), so the override reaches the core/framework objects as well as the
+# application's.  Each variable is optional; when unset, PlatformIO's native
+# gcc/g++ defaults are kept, so ordinary host builds are unaffected.  Compiler
+# *flags* are intentionally left to the caller (e.g. via PLATFORMIO_BUILD_FLAGS)
+# rather than parsed here.
+for _scons_var, _env_var in (
+    ("CC", "TARGET_CC"),
+    ("CXX", "TARGET_CXX"),
+    ("AR", "TARGET_AR"),
+    ("RANLIB", "TARGET_RANLIB"),
+):
+    _tool = os.environ.get(_env_var)
+    if _tool:
+        env.Replace(**{_scons_var: _tool})
+
 # Allow the application to override the output binary name.
 # Set board_build.progname in platformio.ini to change the default "program".
 progname = env.BoardConfig().get("build.progname", "")

cores/ardulinux/linux/gpio/LinuxGPIOPin.cpp

@@ -198,6 +198,16 @@ gpiod_line *LinuxGPIOPin::getLine(const char *chipLabel, const char *linuxPinNam
 	gpiod_line_settings_free(settings);
 	gpiod_chip_close(chip);
 	chip = NULL;  // prevent double-close in ~LinuxGPIOPin()
+	// gpiod_chip_request_lines() returns NULL when the line cannot be acquired
+	// (e.g. already claimed by another process or a kernel driver). Fail loudly
+	// here instead of returning NULL and asserting later in a reconfigure call.
+	if (!line) {
+		char msg[128];
+		snprintf(msg, sizeof(msg),
+			"Error, cannot acquire GPIO line '%s' on %s (already in use?)",
+			linuxPinName ? linuxPinName : "?", chipLabel ? chipLabel : "?");
+		throw std::invalid_argument(msg);
+	}
 	return line;
 #else
 	auto line = gpiod_chip_find_line(chip, linuxPinName);
@@ -240,6 +250,16 @@ gpiod_line *LinuxGPIOPin::getLine(const char *chipLabel, const int linuxPinNum)
 	gpiod_line_settings_free(settings);
 	gpiod_chip_close(chip);
 	chip = NULL;  // prevent double-close in ~LinuxGPIOPin()
+	// gpiod_chip_request_lines() returns NULL when the line cannot be acquired
+	// (e.g. already claimed by another process or a kernel driver). Fail loudly
+	// here instead of returning NULL and asserting later in a reconfigure call.
+	if (!line) {
+		char msg[128];
+		snprintf(msg, sizeof(msg),
+			"Error, cannot acquire GPIO line %d on %s (already in use?)",
+			linuxPinNum, chipLabel ? chipLabel : "?");
+		throw std::invalid_argument(msg);
+	}
 	return line;
 #else
 	auto line = gpiod_chip_get_line(chip, linuxPinNum);