feat(core): aad mock display driver

diff --git a/core/embed/io/Cargo.toml b/core/embed/io/Cargo.toml
index da425ed3..bb29f041 100644
--- a/core/embed/io/Cargo.toml
+++ b/core/embed/io/Cargo.toml
@@ -111,6 +111,7 @@ framebuffer = []
 # to also advertise `framebuffer` in its project.toml. display_st7789 supports
 # both modes — the model.toml decides.
 # The emulator's unix driver is selected by display/build.rs (not a feature).
+display_none = []
 display_ltdc_dsi = ["framebuffer"]
 display_st7789 = []
 display_vg2864 = ["framebuffer"]
diff --git a/core/embed/io/display/build.rs b/core/embed/io/display/build.rs
index 1a1911e1..4794085d 100644
--- a/core/embed/io/display/build.rs
+++ b/core/embed/io/display/build.rs
@@ -23,6 +23,8 @@ pub fn def_module(lib: &mut CLibrary) -> Result<()> {
         // The emulator reuses the emulated board's display configuration (panel,
         // framebuffer) but always builds the unix driver instead of the HW one.
         add_driver_unix(lib)?;
+    } else if cfg!(feature = "display_none") {
+        add_driver_none(lib)?;
     } else if cfg!(feature = "display_ltdc_dsi") {
         add_driver_ltdc_dsi(lib)?;
     } else if cfg!(feature = "display_st7789") {
@@ -110,6 +112,18 @@ fn add_driver_unix(lib: &mut CLibrary) -> Result<()> {
     Ok(())
 }
 
+// Headless driver for boards without a display. Sets nominal resolution
+// defines so dependent code compiles; performs no drawing at runtime.
+fn add_driver_none(lib: &mut CLibrary) -> Result<()> {
+    lib.add_defines([
+        ("USE_RGB_COLORS", Some("1")),
+        ("DISPLAY_RESX", Some("240")),
+        ("DISPLAY_RESY", Some("240")),
+    ]);
+    lib.add_source("display/none/display_driver.c");
+    Ok(())
+}
+
 fn add_driver_ltdc_dsi(lib: &mut CLibrary) -> Result<()> {
     if cfg!(feature = "mcu_stm32u5g") {
         lib.add_sources([
diff --git a/core/embed/io/display/none/display_driver.c b/core/embed/io/display/none/display_driver.c
new file mode 100644
index 00000000..4493c5d8
--- /dev/null
+++ b/core/embed/io/display/none/display_driver.c
@@ -0,0 +1,137 @@
+/*
+ * This file is part of the Trezor project, https://trezor.io/
+ *
+ * Copyright (c) SatoshiLabs
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+// Headless ("none") display driver.
+//
+// Used by boards that have no display hardware (e.g. bare development
+// boards). It implements the full `io/display.h` interface but performs no
+// drawing: all bitblt operations are discarded and there is no framebuffer.
+// This lets the boot chain (boardloader/bootloader) link and run on
+// display-less hardware while the UI code keeps working (it simply renders to
+// nowhere).
+
+#include <trezor_rtl.h>
+
+#include <io/display.h>
+
+// All display entry points live in the kernel; the unprivileged side reaches
+// them through syscall stubs (sys/syscall/.../syscall_stubs.c). Gating the
+// whole driver on KERNEL_MODE avoids duplicate definitions in firmware builds.
+#ifdef KERNEL_MODE
+
+typedef struct {
+  // Set if the driver is initialized
+  bool initialized;
+  // Current display orientation (always 0)
+  int orientation_angle;
+  // Current backlight level ranging from 0 to 255
+  uint8_t backlight_level;
+} display_driver_t;
+
+static display_driver_t g_display_driver = {
+    .initialized = false,
+};
+
+bool display_init(display_content_mode_t mode) {
+  display_driver_t *drv = &g_display_driver;
+
+  if (drv->initialized) {
+    return true;
+  }
+
+  drv->backlight_level = 0;
+  drv->orientation_angle = 0;
+  drv->initialized = true;
+  return true;
+}
+
+void display_deinit(display_content_mode_t mode) {
+  display_driver_t *drv = &g_display_driver;
+  drv->initialized = false;
+}
+
+void display_set_unpriv_access(bool unpriv) {}
+
+bool display_set_backlight(uint8_t level) {
+  display_driver_t *drv = &g_display_driver;
+
+  if (!drv->initialized) {
+    return false;
+  }
+
+  drv->backlight_level = level;
+  return true;
+}
+
+uint8_t display_get_backlight(void) {
+  display_driver_t *drv = &g_display_driver;
+
+  if (!drv->initialized) {
+    return 0;
+  }
+
+  return drv->backlight_level;
+}
+
+int display_set_orientation(int angle) {
+  display_driver_t *drv = &g_display_driver;
+
+  if (!drv->initialized) {
+    return 0;
+  }
+
+  // The headless driver only supports the default orientation.
+  if (angle == 0) {
+    drv->orientation_angle = angle;
+  }
+  return drv->orientation_angle;
+}
+
+int display_get_orientation(void) {
+  display_driver_t *drv = &g_display_driver;
+
+  if (!drv->initialized) {
+    return 0;
+  }
+
+  return drv->orientation_angle;
+}
+
+#ifdef FRAMEBUFFER
+
+bool display_get_frame_buffer(display_fb_info_t *fb) {
+  memset(fb, 0, sizeof(display_fb_info_t));
+  return false;
+}
+
+#else  // FRAMEBUFFER
+
+void display_wait_for_sync(void) {}
+
+#endif
+
+void display_refresh(void) {}
+
+void display_fill(const gfx_bitblt_t *bb) {}
+
+void display_copy_rgb565(const gfx_bitblt_t *bb) {}
+
+void display_copy_mono1p(const gfx_bitblt_t *bb) {}
+
+#endif  // KERNEL_MODE