Keyboard privacy - mockup WiP

src/board/system76/common/include/board/options.h

@@ -24,6 +24,8 @@ enum {
     OPT_ALLOW_BAT_BOOST,
     OPT_ALWAYS_ON_USB,
     OPT_GPU_MUX_CTRL,
+    OPT_KB_PRIVACY,
+    OPT_KB_PRIVACY_MAX_DELAY,
     NUM_OPTIONS
 };
 

src/board/system76/common/kbscan.c

@@ -3,6 +3,7 @@
 #include <arch/delay.h>
 #include <arch/time.h>
 #include <board/acpi.h>
+#include <board/options.h>
 #include <board/fan.h>
 #include <board/gpio.h>
 #include <board/keymap.h>
@@ -23,6 +24,17 @@
 bool kbscan_fn_held = false;
 bool kbscan_esc_held = false;
 
+bool kb_privacy_enabled = false;
+static uint16_t kb_privacy_lfsr;
+
+static uint8_t kb_privacy_rand(uint8_t max) {
+    if (!kb_privacy_lfsr)
+        kb_privacy_lfsr = (uint16_t)(time_get() | 1u);
+    uint16_t bit = kb_privacy_lfsr & 1u;
+    kb_privacy_lfsr = (kb_privacy_lfsr >> 1) ^ (uint16_t)(bit ? 0xB400u : 0u);
+    return (uint8_t)(kb_privacy_lfsr % max);
+}
+
 bool kbscan_enabled = false;
 uint16_t kbscan_repeat_period = 91;
 uint16_t kbscan_repeat_delay = 500;
@@ -58,6 +70,8 @@ void kbscan_init(void) {
     KSIGCTRL = 0;
     KSIGOEN = 0;
     KSIGDAT = 0;
+
+    kb_privacy_enabled = (bool)options_get(OPT_KB_PRIVACY);
 }
 
 // Debounce time in milliseconds
@@ -208,9 +222,21 @@ bool kbscan_press(uint16_t key, bool pressed, uint8_t *layer) {
         return true;
     }
 
+    if (key == K_KB_PRIVACY && pressed) {
+        DEBUG("Toggling KB privacy\n");
+        kb_privacy_enabled ^= 1;
+        options_set(OPT_KB_PRIVACY, (uint8_t)kb_privacy_enabled);
+        return true;
+    }
+
     switch (key & KT_MASK) {
     case (KT_NORMAL):
         if (kbscan_enabled) {
+            if (kb_privacy_enabled) {
+                uint8_t max_delay = options_get(OPT_KB_PRIVACY_MAX_DELAY);
+                if (max_delay)
+                    delay_ms(kb_privacy_rand(max_delay));
+            }
             kbc_scancode(key, pressed);
         }
         break;

src/board/system76/common/options.c

@@ -17,6 +17,8 @@ uint8_t DEFAULT_OPTIONS[NUM_OPTIONS] = {
     [OPT_ALLOW_BAT_BOOST] = 0,
     [OPT_ALWAYS_ON_USB] = 0,
     [OPT_GPU_MUX_CTRL] = 0,
+    [OPT_KB_PRIVACY] = 0,
+    [OPT_KB_PRIVACY_MAX_DELAY] = 100,
 };
 // clang-format on
 

src/common/include/common/keymap.h

@@ -284,5 +284,6 @@ uint16_t keymap_translate(uint16_t key);
 
 #define KF_CUSTOM (0x0200)
 #define K_FNLOCK (KF_CUSTOM | 0x01)
+#define K_KB_PRIVACY (KF_CUSTOM | 0x02)
 
 #endif // _COMMON_KEYMAP_H

src/keyboard/system76/14in_83/keymap/default.c

@@ -19,7 +19,7 @@ LAYOUT(
     K_ESC, K_TOUCHPAD, K_DISPLAY_TOGGLE, K_MUTE, K_KBD_BKL, K_VOLUME_DOWN, K_VOLUME_UP, K_DISPLAY_MODE, K_BRIGHTNESS_DOWN, K_BRIGHTNESS_UP, K_CAMERA_TOGGLE, K_AIRPLANE_MODE, K_SUSPEND, K_HOME, K_END, K_PRINT_SCREEN, K_DEL,
     K_PLAY_PAUSE, K_FAN_TOGGLE, K_2, K_3, K_4, K_5, K_6, K_7, K_8, K_9, K_0, K_MINUS, K_EQUALS, K_BKSP,
     K_TAB, K_Q, K_W, K_E, K_R, K_T, K_Y, K_U, K_I, K_O, K_P, K_BRACE_OPEN, K_BRACE_CLOSE, K_BACKSLASH,
-    K_FNLOCK, K_A, K_S, K_D, K_F, K_G, K_H, K_J, K_K, K_L, K_SEMICOLON, K_QUOTE, K_ENTER,
+    K_FNLOCK, K_A, K_KB_PRIVACY, K_D, K_F, K_G, K_H, K_J, K_K, K_L, K_SEMICOLON, K_QUOTE, K_ENTER,
     K_LEFT_SHIFT, K_Z, K_X, K_C, K_V, K_B, K_N, K_M, K_COMMA, K_PERIOD, K_SLASH, K_RIGHT_SHIFT,
     K_LEFT_CTRL, KT_FN, K_LEFT_SUPER, K_LEFT_ALT, K_SPACE, K_RIGHT_ALT, K_APP, K_PGUP, K_UP, K_PGDN,
     K_LEFT, K_DOWN, K_RIGHT