I put the LEDs into my NKRO report, but I probably don't need to (now that I run both at the same time).
I don't switch as such, but the report descriptor for the Boot endpoint tells the host that there are no keys iin it. When in Boot protocol mode I inhibit output from anything other than the Boot endpoint.
This is my NKRO descriptor (with the Media key and the Linux bug fixes removed, since they complicate it)...
#define USB_FIRST_KEY_BIT 1
#define USB_LAST_KEY_BIT 0xA4
#define USB_NUM_KEY_BITS (USB_LAST_KEY_BIT - USB_FIRST_KEY_BIT + 1)
#define USB_NUM_KEY_BIT_BYTES ((USB_NUM_KEY_BITS + 7) / 8)
#define USB_NUM_PADDING_KEY_BITS (8 * USB_NUM_KEY_BIT_BYTES - USB_NUM_KEY_BITS)
static uint8_t PROGMEM keyboard_hid_report_desc[] = {
0x05, 0x01, // Usage Page (Generic Desktop),
0x09, 0x06, // Usage (Keyboard),
0xA1, 0x01, // Collection (Application),
0x75, 0x01, // Report Size (1),
0x95, 0x08, // Report Count (8),
0x05, 0x07, // Usage Page (Key Codes),
0x19, 0xE0, // Usage Minimum (224),
0x29, 0xE7, // Usage Maximum (231),
0x15, 0x00, // Logical Minimum (0),
0x25, 0x01, // Logical Maximum (1),
0x81, 0x02, // Input (Data, Variable, Absolute), ;Modifier byte
0x95, 0x05, // Report Count (5),
0x75, 0x01, // Report Size (1),
0x05, 0x08, // Usage Page (LEDs),
0x19, 0x01, // Usage Minimum (1),
0x29, 0x05, // Usage Maximum (5),
0x91, 0x02, // Output (Data, Variable, Absolute), ;LED report
0x95, 0x01, // Report Count (1),
0x75, 0x03, // Report Size (3),
0x91, 0x03, // Output (Constant), ;LED report padding
0x75, 0x01, // Report Size (1),
0x95, USB_NUM_KEY_BITS, // Report Count (),
0x05, 0x07, // Usage Page (Key Codes),
0x19, USB_FIRST_KEY_BIT, // Usage Minimum (),
0x29, USB_LAST_KEY_BIT, // Usage Maximum (),
0x15, 0x00, // Logical Minimum (0),
0x25, 0x01, // Logical Maximum (1),
0x81, 0x02, // Input (Data, Variable, Absolute), ;keys bit array
#if USB_NUM_PADDING_KEY_BITS
0x95, USB_NUM_PADDING_KEY_BITS, // Report Count (),
0x75, 0x01, // Report Size (1),
0x81, 0x03, // Input (Constant), ;Padding
#endif
0xC0, // End Collection
};