misc: do not hang if graphics backend is not available

CHANGELOG.md

@@ -12,6 +12,7 @@ If a change only affects particular applications, they are listed in parentheses
 
 - misc: Use standard C library instead of builtin functions (!49, thanks @vstoiakin)
 - feat: Add support for split packaging of buffyboard and unl0kr (!54, thanks @vstoiakin)
+- fix: Do not hang if graphics backend is not available (!57, thanks @vstoiakin)
 
 ## 3.3.0 (2025-04-15)
 

buffyboard/main.c

@@ -221,6 +221,10 @@ int main(int argc, char *argv[]) {
 
     /* Initialise display */
     lv_display_t *disp = lv_linux_fbdev_create();
+    if (access("/dev/fb0", F_OK) != 0) {
+        bbx_log(BBX_LOG_LEVEL_ERROR, "/dev/fb0 is not available");
+        sigaction_handler(SIGTERM);
+    }
     lv_linux_fbdev_set_file(disp, "/dev/fb0");
     if (conf_opts.quirks.fbdev_force_refresh) {
         lv_linux_fbdev_set_force_refresh(disp, true);

unl0kr/main.c

@@ -25,7 +25,6 @@
 #include <unistd.h>
 
 #include <sys/reboot.h>
-#include <sys/stat.h>
 #include <sys/time.h>
 
 
@@ -193,6 +192,11 @@ static void shutdown(void);
  */
 static void sigaction_handler(int signum);
 
+/**
+ * Restore the terminal and exit from the program with EXIT_FAILURE.
+ */
+static void exit_failure();
+
 
 /**
  * Static functions
@@ -372,6 +376,11 @@ static void sigaction_handler(int signum) {
     exit(0);
 }
 
+static void exit_failure() {
+    ul_terminal_reset_current_terminal();
+    exit(EXIT_FAILURE);
+}
+
 
 /**
  * Main
@@ -423,6 +432,10 @@ int main(int argc, char *argv[]) {
     case UL_BACKENDS_BACKEND_FBDEV:
         bbx_log(BBX_LOG_LEVEL_VERBOSE, "Using framebuffer backend");
         disp = lv_linux_fbdev_create();
+        if (access("/dev/fb0", F_OK) != 0) {
+            bbx_log(BBX_LOG_LEVEL_ERROR, "/dev/fb0 is not available");
+            exit_failure();
+        }
         lv_linux_fbdev_set_file(disp, "/dev/fb0");
         if (conf_opts.quirks.fbdev_force_refresh) {
             lv_linux_fbdev_set_force_refresh(disp, true);
@@ -434,27 +447,28 @@ int main(int argc, char *argv[]) {
         bbx_log(BBX_LOG_LEVEL_VERBOSE, "Using DRM backend");
         disp = lv_linux_drm_create();
 
-        char *format_string = "/dev/dri/card%d";
-        char drm_path[16] = {0};
-        struct stat buffer;
+        char drm_path[16];
+        bool found = false;
+        for (int i = 0; i < 9; i++) {
+            sprintf(drm_path, "/dev/dri/card%d", i);
 
-        for (size_t i = 0; i < 9; i++) {
-            sprintf(drm_path, format_string, i);
-
-            if (stat(drm_path, &buffer) != 0) {
-                continue;
+            if (access(drm_path, F_OK) == 0) {
+                found = true;
+                break;
             }
-
-            lv_linux_drm_set_file(disp, drm_path, -1);
-
-            break;
         }
+        if (!found) {
+            bbx_log(BBX_LOG_LEVEL_ERROR, "/dev/dri/card* are not available");
+            exit_failure();
+        }
+
+        lv_linux_drm_set_file(disp, drm_path, -1);
 
         break;
 #endif /* LV_USE_LINUX_DRM */
     default:
         bbx_log(BBX_LOG_LEVEL_ERROR, "Unable to find suitable backend");
-        exit(EXIT_FAILURE);
+        exit_failure();
     }
 
     /* Override display properties with command line options if necessary */

unl0kr/terminal.c

@@ -26,50 +26,6 @@ static int current_fd = -1;
 static int original_mode = -1;
 static int original_kb_mode = -1;
 
-
-/**
- * Static prototypes
- */
-
-/**
- * Close the current file descriptor and reopen /dev/tty0.
- * 
- * @return true if opening was successful, false otherwise
- */
-static bool reopen_current_terminal(void);
-
-/**
- * Close the current file descriptor.
- */
-static void close_current_terminal(void);
-
-
-/**
- * Static functions
- */
-
-static bool reopen_current_terminal(void) {
-    close_current_terminal();
-
-    current_fd = open("/dev/tty0", O_RDWR);
-	if (current_fd < 0) {
-        bbx_log(BBX_LOG_LEVEL_WARNING, "Could not open /dev/tty0");
-		return false;
-	}
-
-    return true;
-}
-
-static void close_current_terminal(void) {
-    if (current_fd < 0) {
-        return;
-    }
-
-    close(current_fd);
-    current_fd = -1;
-}
-
-
 /**
  * Public functions
  */
@@ -80,11 +36,10 @@ void ul_terminal_prepare_current_terminal(bool enable_graphics_mode, bool disabl
         return;
     }
 
-    /* Reopen the current terminal */
-    reopen_current_terminal();
-
+    /* Open the current terminal */
+    current_fd = open("/dev/tty0", O_RDWR);
     if (current_fd < 0) {
-        bbx_log(BBX_LOG_LEVEL_WARNING, "Could not prepare current terminal");
+        bbx_log(BBX_LOG_LEVEL_WARNING, "Could not open /dev/tty0");
         return;
     }
 
@@ -128,5 +83,6 @@ void ul_terminal_reset_current_terminal(void) {
         bbx_log(BBX_LOG_LEVEL_WARNING, "Could not reset terminal keyboard mode");
     }
 
-    close_current_terminal();
+    close(current_fd);
+    current_fd = -1;
 }