Adding NKRO virtual dip-switch, using existing bit in keymap byte.

This takes the last, reserved bit there, but doesn't necessitate
a revision to the magic number because it doesn't alter byte order.
Add reference to NKRO virtual dip-switch to documentation.

README.md

@@ -151,6 +151,7 @@ To avoid configuring accidentally additive salt key `KC_SPACE` also needs to be
 - Disable Gui(`Left Gui`)
 - Swap Grave and Escape(`Grave`)
 - Swap BackSlash and BackSpace(`Back Slash`)
+- Enable NKRO on boot(`N`)
 
 #### Default Layer
 - Set Default Layer to 0(`0`)

common/bootmagic.c

@@ -5,6 +5,7 @@
 #include "bootloader.h"
 #include "debug.h"
 #include "keymap.h"
+#include "host.h"
 #include "action_layer.h"
 #include "eeconfig.h"
 #include "bootmagic.h"
@@ -76,8 +77,15 @@ void bootmagic(void)
     if (bootmagic_scan_keycode(BOOTMAGIC_KEY_SWAP_BACKSLASH_BACKSPACE)) {
         keymap_config.swap_backslash_backspace = !keymap_config.swap_backslash_backspace;
     }
+    if (bootmagic_scan_keycode(BOOTMAGIC_HOST_NKRO)) {
+        keymap_config.nkro = !keymap_config.nkro;
+    }
     eeconfig_write_keymap(keymap_config.raw);
 
+#ifdef NKRO_ENABLE
+    keyboard_nkro = keymap_config.nkro;
+#endif
+
     /* default layer */
     uint8_t default_layer = 0;
     if (bootmagic_scan_keycode(BOOTMAGIC_KEY_DEFAULT_LAYER_0)) { default_layer |= (1<<0); }

common/bootmagic.h

@@ -60,6 +60,9 @@
 #ifndef BOOTMAGIC_KEY_SWAP_BACKSLASH_BACKSPACE
 #define BOOTMAGIC_KEY_SWAP_BACKSLASH_BACKSPACE  KC_BSLASH
 #endif
+#ifndef BOOTMAGIC_HOST_NKRO
+#define BOOTMAGIC_HOST_NKRO              KC_N
+#endif
 
 
 /*

common/command.c

@@ -151,6 +151,7 @@ static void print_eeconfig(void)
     print(".no_gui: "); print_dec(kc.no_gui); print("\n");
     print(".swap_grave_esc: "); print_dec(kc.swap_grave_esc); print("\n");
     print(".swap_backslash_backspace: "); print_dec(kc.swap_backslash_backspace); print("\n");
+    print(".nkro: "); print_dec(kc.nkro); print("\n");
 
 #ifdef BACKLIGHT_ENABLE
     backlight_config_t bc;

common/eeconfig.h

@@ -47,6 +47,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #define EECONFIG_KEYMAP_NO_GUI                      (1<<4)
 #define EECONFIG_KEYMAP_SWAP_GRAVE_ESC              (1<<5)
 #define EECONFIG_KEYMAP_SWAP_BACKSLASH_BACKSPACE    (1<<6)
+#define EECONFIG_KEYMAP_NKRO                        (1<<7)
 
 
 bool eeconfig_is_enabled(void);

common/keymap.h

@@ -35,7 +35,7 @@ typedef union {
         bool no_gui:1;
         bool swap_grave_esc:1;
         bool swap_backslash_backspace:1;
-        bool reserved:1;
+        bool nkro:1;
     };
 } keymap_config_t;
 keymap_config_t keymap_config;