From 70eee9942e74e05335a68d0d281b992e766fe367 Mon Sep 17 00:00:00 2001
From: Dee Newcum <dee.newcum@gmail.com>
Date: Fri, 11 Feb 2022 10:20:28 -0600
Subject: [PATCH 1/2] improve error handling

---
 pi400.c | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/pi400.c b/pi400.c
index cb5f013..4f822d3 100644
--- a/pi400.c
+++ b/pi400.c
@@ -14,6 +14,7 @@
 #include <unistd.h>
 #include <string.h>
 #include <stdlib.h>
+#include <dirent.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 
@@ -36,6 +37,24 @@ void signal_handler(int dummy) {
     running = 0;
 }
 
+void prechecks(char *argv0) {
+    DIR *dir;
+
+    if (geteuid() != 0) {
+        printf("Error: %s must be run as root.\n", argv0);
+        exit(1);
+    }
+
+    // is the 'dwc2' module properly loaded?
+    dir = opendir("/sys/module/dwc2");
+    if (!dir || errno == ENOENT) {
+        printf("Error: This must be added to /boot/config.txt and the system rebooted:\n");
+        printf("    dtoverlay=dwc2\n");
+        exit(1);
+    }
+    closedir(dir);
+}
+
 bool modprobe_libcomposite() {
     pid_t pid;
 
@@ -154,7 +173,9 @@ void send_empty_hid_reports_both() {
     }
 }
 
-int main() {
+int main(int argc, char *argv[]) {
+    prechecks(argv[0]);
+
     modprobe_libcomposite();
 
     keyboard_buf.report_id = 1;

From fa285bfd45aa3d14a89c0c5c118618d47627cfc9 Mon Sep 17 00:00:00 2001
From: Dee Newcum <dee.newcum@gmail.com>
Date: Fri, 11 Feb 2022 15:23:21 -0600
Subject: [PATCH 2/2] wrap prechecks() in #ifdef NO_OUTPUT

---
 pi400.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/pi400.c b/pi400.c
index 4f822d3..5b69be9 100644
--- a/pi400.c
+++ b/pi400.c
@@ -174,7 +174,9 @@ void send_empty_hid_reports_both() {
 }
 
 int main(int argc, char *argv[]) {
+#ifndef NO_OUTPUT
     prechecks(argv[0]);
+#endif
 
     modprobe_libcomposite();