Initial version.

.gitignore

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+powermate
+
+Thumbs.db
+.DS_Store
+*.swp

Makefile

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+powermate: main.c
+	gcc -o powermate main.c -O2 -s

README.md

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+# PowerMate Linux Driver
+
+This is a small Linux input driver for the Griffin PowerMate. Tested only on Ubuntu 14.10.
+
+
+# Disclaimer
+
+PowerMate is a registered trademark of Griffin Technologies Inc. This software is not affiliated or endorsed by them.
+
+
+# Installation
+
+Create a udev rule by creating the file `/etc/udev/rules.d/60-powermate.rules`
+
+```
+ACTION=="add", ENV{ID_USB_DRIVER}=="powermate", SYMLINK+="input/powermate", MODE="0666"
+```
+
+After creating the file, unplug and plug the PowerMate back in.
+
+Compile the executable with `make` and run it with `./powermate`.
+
+Make it run automatically on login somehow. The script should handle the device being disconnected and connected without problems.

main.c

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+#include <stdio.h>
+#include <linux/input.h>
+
+int main(int argc, char *argv[]) {
+  // if (argc < 3) {
+  //   fprintf(stderr, "Usage: %s /dev/input/powermate 1\n", argv[0]);
+  //   fprintf(stderr, "The number is the percentage to change the volume with each input event.\n");
+  //   return 1;
+  // }
+  // char *dev = argv[1];
+  // int p = atoi(argv[2]);
+
+  char dev[] = "/dev/input/powermate";
+  int p = 2;
+
+  // Test device
+  FILE *f = fopen(dev, "rb");
+  if (f == NULL) {
+    fprintf(stderr, "Could not open %s\n", dev);
+    return 2;
+  }
+  fclose(f);
+
+  // daemonize
+  int pid = fork();
+  if (pid == 0) {
+    // We're the child process!
+    // Release handle to working directory
+    chdir("/");
+    // Close things
+    fclose(stdin);
+    fclose(stdout);
+    fclose(stderr);
+  }
+  else if (pid < 0) {
+    fprintf(stderr, "Failed to become a daemon, whatevs.\n");
+  }
+  else {
+    printf("Just became a daemon, deal with it!\n");
+    return 0;
+  }
+
+  while (1) {
+    do {
+      f = fopen(dev, "rb");
+      if (f == NULL) {
+        fprintf(stderr, "Could not open %s\n", dev);
+        fprintf(stderr, "Sleeping 1 second.\n");
+        sleep(1);
+      }
+    } while (f == NULL);
+
+    while (!feof(f) && !ferror(f)) {
+      struct input_event ev;
+      size_t n = fread(&ev, 1, sizeof(ev), f);
+      // fprintf(stderr, "type: %d\n", ev.type);
+      // fprintf(stderr, "code: %d\n", ev.code);
+      // fprintf(stderr, "value: %d\n", ev.value);
+      // fprintf(stderr, "\n");
+      // fflush(stderr);
+
+      if (ev.type == 2 && ev.code == 7) {
+        char buf[100];
+        if (ev.value == -1) {
+          // counter clock-wise turn
+          sprintf(buf, "amixer -D pulse sset Master %d%%-", p);
+          system(buf);
+        }
+        else if (ev.value == 1) {
+          // clock-wise turn
+          sprintf(buf, "amixer -D pulse sset Master %d%%+", p);
+          system(buf);
+        }
+      }
+      if (ev.type == 1 && ev.code == 256) {
+        if (ev.value == 1) {
+          // knob depressed
+          system("amixer -D pulse set Master toggle");
+        }
+        else if (ev.value == 0) {
+          // knob released
+        }
+      }
+    }
+    fprintf(stderr, "Device disappeared.\n");
+    fclose(f);
+  }
+
+  return 0;
+}