View difference between Paste ID: zK8jH2A1 and grZPxRDu

 //
 // Simple hack to change dpi on Logitech G400s
 // G400s only support: 400, 800, 1600, 2000 and 4000 dpi, all other are interpolate by software
 //
 // Based on g400_hack from Przemek Aksamit
 // https://bitbucket.org/extaliones/g400_hack/src
 //
 // gcc -lusb-1.0 -o g400s_hack g400s_hack.c
 //
 
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <libusb-1.0/libusb.h>
 
 #define G400S_VENDOR_ID   0x046d
 #define G400S_PRODUCT_ID  0xc24c
 
 #define EXIT_SUCCESS       0
 #define EXIT_ERROR_ARGS    1
 #define EXIT_ERROR_DEVICE  2
 #define EXIT_ERROR_KERNEL  3
 #define EXIT_ERROR_CLAIM   4
 #define EXIT_ERROR_WRITE   5
 
 
 libusb_context *ctx = NULL;
 libusb_device_handle *handle = NULL;
 
 int detached = 0;
 int claimed  = 0;
 
 
 void usage()
 {
-  printf("Usage: ./g400s_hack ( -400 | -800 | -1600 | -2000 | -4000 )\n");
+  printf("Usage: ./g400s_hack ( -400 | -800 | -1600 | -2000 | -4000 | -d | -n)\n");
   printf("Highly experimental, use with caution.\n");
 }
 
 void cleanup()
 {
   if (claimed)
     libusb_release_interface(handle, 1);
 
   if (detached)
     libusb_attach_kernel_driver(handle, 1);
 
   libusb_close(handle);
   libusb_exit(ctx);
 }
 
 int main(int argc, char **argv)
 {
   if (argc != 2 || argv[1][0] != '-') {
     usage();
     return EXIT_ERROR_ARGS;
   }
 
   //131 => 400dpi, 132 => 800dpi, 133 => 1600dpi, 134 => 2000dpi, 135 => 4000dpi
   uint16_t dpi_idx = 131;
   if      (strcmp(&argv[1][1], "400" ) == 0)
     dpi_idx += 0;
   else if (strcmp(&argv[1][1], "800" ) == 0)
     dpi_idx += 1;
   else if (strcmp(&argv[1][1], "1600") == 0)
     dpi_idx += 2;
   else if (strcmp(&argv[1][1], "2000") == 0)
     dpi_idx += 3;
   else if (strcmp(&argv[1][1], "4000") == 0)
     dpi_idx += 4;
   else if (strcmp(&argv[1][1], "d") == 0)
     dpi_idx = 0;
   else if (strcmp(&argv[1][1], "n") == 0)
     dpi_idx = 4;
   else {
-  printf("Set new DPI: %s (index %i)\n", &argv[1][1], dpi_idx);
+
     return EXIT_ERROR_ARGS;
   }
 
   if (dpi_idx >= 131) {
     printf("Set new DPI: %s (index %i)\n", &argv[1][1], dpi_idx);
   }
   else {
     printf("Set Driver/Native mode: %s (index %i)\n", &argv[1][1], dpi_idx);
   }
 
   libusb_init(&ctx);
 
   handle = libusb_open_device_with_vid_pid(ctx, G400S_VENDOR_ID, G400S_PRODUCT_ID);
   libusb_set_debug(ctx, 3);
 
   if (!handle) {
     fprintf(stderr, "Logitech G400s not found! (Do you have usb rights? Try with sudo?)\n");
     cleanup();
     return EXIT_ERROR_DEVICE;
   }
 
   if (libusb_kernel_driver_active(handle, 1) == 1) {
     if (libusb_detach_kernel_driver(handle, 1) != 0) {
       fprintf(stderr, "Can't detach kernel driver.\n");
       cleanup();
       return EXIT_ERROR_KERNEL;
     }
 
     detached = 1;
   }
 
   if (libusb_claim_interface(handle, 1) != 0) {
     fprintf(stderr, "Failed to claim interface.\n");
     cleanup();
     return EXIT_ERROR_CLAIM;
   }
 
   claimed = 1;
 
   if (dpi_idx == 0) {
     // Set driver mode, then DPI to 400
     char data[2];
     data[0] = 0x20; data[1] = 0x01;
     int result = libusb_control_transfer (handle, 0x21, 9, 0x0320, 1, data, 2, 1000);
     if (result != 2) {
       fprintf(stderr, "Error writing to USB device (%d).\n", result);
       cleanup();
       return EXIT_ERROR_WRITE;
     }
     dpi_idx = 131;
   }
 
   if (libusb_control_transfer (handle, 0x40, 2, 0x008e, dpi_idx, NULL, 0, 1000) != 0) {
     fprintf(stderr, "Error writing to USB device.\n");
     cleanup();
     return EXIT_ERROR_WRITE;
   }
 
   cleanup();
   printf("Finished.\n");
   return EXIT_SUCCESS;
 }