Create an inputcat binary

flake.nix

@@ -14,6 +14,11 @@
       packages.${system} =
         {
           kobo-color-inputdev = pkgs.callPackage ./default.nix { };
+
+	  # Cross compile to run on the kobo itself
+          cross.armv7l-unknown-linux-musleabihf.kobo-color-inputdev =
+            pkgs.pkgsCross.armv7l-hf-multiplatform.pkgsStatic.callPackage ./default.nix { };
+
           default = self.packages.${system}.kobo-color-inputdev;
         };
       devShells.${system}.default = import ./shell.nix { inherit pkgs; };

meson.build

@@ -4,3 +4,6 @@ project('kobo-color-inputdev', 'c',
 
 main = executable('kobo-color-inputdev', ['src/main.c', './src/device.c'],
   install : true)
+
+inputcat = executable('inputcat', ['src/inputcat.c'],
+  install : true)

src/inputcat.c

@@ -0,0 +1,75 @@
+#include <errno.h>
+#include <fcntl.h>
+#include <linux/input.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <unistd.h>
+
+#define EXECUTABLE_NAME "inputcat"
+#define DEFAULT_INPUTDEV "/dev/input/event1"
+
+int write_all(int fd, char *buf, int n) {
+  int written = 0;
+  int res = 0;
+  while (res >= 0 && written < n) {
+    res = write(fd, buf + written, n - written);
+    written += res;
+  };
+  if (res >= 0) {
+    return 0;
+  }
+  return res;
+}
+
+int cat(int fd) {
+  char buf[4096];
+  int res = 0;
+
+  while (!res) {
+    int n = read(fd, buf, sizeof(buf));
+    res = write_all(STDOUT_FILENO, buf, n);
+  }
+
+  if (res != EOF) {
+    fprintf(stderr, "Error writing input events to stdout: %s! Aborting\n",
+            strerror(res));
+    return EXIT_FAILURE;
+  }
+
+  return EXIT_SUCCESS;
+}
+
+void print_usage(void) {
+  printf("Usage: %s [INPUT]\n"
+         "Grab exclusive access to INPUT and write it's events to stdout\n\n"
+         "If not specified %s will be used",
+         EXECUTABLE_NAME, DEFAULT_INPUTDEV);
+}
+
+int main(int argc, char **argv) {
+  char *input_dev = "/dev/input/event1";
+  if (argc > 2) {
+    print_usage();
+    return EXIT_FAILURE;
+  }
+  if (argc == 2) {
+    input_dev = argv[1];
+  }
+
+  int src = open(input_dev, O_RDONLY);
+  if (ioctl(src, EVIOCGRAB, 1)) {
+    fprintf(stderr, "Error grabbing exclusive access to event device %s: %s\n",
+            input_dev, strerror(errno));
+    return EXIT_FAILURE;
+  }
+
+  int res = cat(src);
+
+  ioctl(src, EVIOCGRAB, 0);
+  close(src);
+
+  return res;
+}