Kernel: Add option to force using only the bootloader framebuffer

This allows forcing the use of only the framebuffer set up by the
bootloader and skips instantiating devices for any other graphics
cards that may be present.

Base/usr/share/man/man7/boot_parameters.md

@@ -41,7 +41,7 @@ List of options:
   but only if **`acpi`** is set to **`limited`** or **`on`**, and a `MADT` (APIC) table is available.
   Otherwise, the kernel will fallback to use the i8259 PICs.
 
-* **`fbdev`** - This parameter expects **`on`** or **`off`**.
+* **`fbdev`** - This parameter expects one of the following values. **`on`**- Boot into the graphical environment (default). **`off`** - Boot into text mode. **`bootloader`** - Boot into the graphical environment, but only use the frame buffer set up by the bootloader and do not initialize any other graphics cards.
 
 * **`force_pio`** - If present on the command line, the IDE controllers will be force into PIO mode when initialized IDE Channels on boot.
 

Kernel/CommandLine.cpp

@@ -245,9 +245,14 @@ PanicMode CommandLine::panic_mode(Validate should_validate) const
     return PanicMode::Halt;
 }
 
-UNMAP_AFTER_INIT bool CommandLine::are_framebuffer_devices_enabled() const
+UNMAP_AFTER_INIT auto CommandLine::are_framebuffer_devices_enabled() const -> FrameBufferDevices
 {
-    return lookup("fbdev"sv).value_or("on"sv) == "on"sv;
+    const auto fbdev_value = lookup("fbdev"sv).value_or("on"sv);
+    if (fbdev_value == "on"sv)
+        return FrameBufferDevices::Enabled;
+    if (fbdev_value == "bootloader"sv)
+        return FrameBufferDevices::BootloaderOnly;
+    return FrameBufferDevices::ConsoleOnly;
 }
 
 StringView CommandLine::userspace_init() const

Kernel/CommandLine.h

@@ -52,6 +52,12 @@ public:
         No,
     };
 
+    enum class FrameBufferDevices {
+        Enabled,
+        ConsoleOnly,
+        BootloaderOnly
+    };
+
     [[nodiscard]] const String& string() const { return m_string; }
     Optional<StringView> lookup(StringView key) const;
     [[nodiscard]] bool contains(StringView key) const;
@@ -65,7 +71,7 @@ public:
     [[nodiscard]] bool is_vmmouse_enabled() const;
     [[nodiscard]] PCIAccessLevel pci_access_level() const;
     [[nodiscard]] bool is_legacy_time_enabled() const;
-    [[nodiscard]] bool are_framebuffer_devices_enabled() const;
+    [[nodiscard]] FrameBufferDevices are_framebuffer_devices_enabled() const;
     [[nodiscard]] bool is_force_pio() const;
     [[nodiscard]] AcpiFeatureLevel acpi_feature_level() const;
     [[nodiscard]] StringView system_mode() const;

Kernel/Graphics/GraphicsManagement.cpp

@@ -36,9 +36,14 @@ UNMAP_AFTER_INIT GraphicsManagement::GraphicsManagement()
 {
 }
 
-bool GraphicsManagement::framebuffer_devices_allowed() const
+bool GraphicsManagement::framebuffer_devices_use_bootloader_framebuffer() const
 {
-    return kernel_command_line().are_framebuffer_devices_enabled();
+    return kernel_command_line().are_framebuffer_devices_enabled() == CommandLine::FrameBufferDevices::BootloaderOnly;
+}
+
+bool GraphicsManagement::framebuffer_devices_console_only() const
+{
+    return kernel_command_line().are_framebuffer_devices_enabled() == CommandLine::FrameBufferDevices::ConsoleOnly;
 }
 
 void GraphicsManagement::deactivate_graphical_mode()
@@ -73,7 +78,7 @@ UNMAP_AFTER_INIT bool GraphicsManagement::determine_and_initialize_graphics_devi
     VERIFY(is_vga_compatible_pci_device(device_identifier) || is_display_controller_pci_device(device_identifier));
     auto add_and_configure_adapter = [&](GenericGraphicsAdapter& graphics_device) {
         m_graphics_devices.append(graphics_device);
-        if (!framebuffer_devices_allowed()) {
+        if (framebuffer_devices_console_only()) {
             graphics_device.enable_consoles();
             return;
         }
@@ -81,6 +86,22 @@ UNMAP_AFTER_INIT bool GraphicsManagement::determine_and_initialize_graphics_devi
     };
 
     RefPtr<GenericGraphicsAdapter> adapter;
+
+    auto create_bootloader_framebuffer_device = [&]() {
+        if (multiboot_framebuffer_type == MULTIBOOT_FRAMEBUFFER_TYPE_RGB) {
+            dmesgln("Graphics: Using a preset resolution from the bootloader");
+            adapter = VGACompatibleAdapter::initialize_with_preset_resolution(device_identifier,
+                multiboot_framebuffer_addr,
+                multiboot_framebuffer_width,
+                multiboot_framebuffer_height,
+                multiboot_framebuffer_pitch);
+        }
+    };
+
+    if (framebuffer_devices_use_bootloader_framebuffer())
+        create_bootloader_framebuffer_device();
+
+    if (!adapter) {
         switch (device_identifier.hardware_id().vendor_id) {
         case PCI::VendorID::QEMUOld:
             if (device_identifier.hardware_id().device_id == 0x1111)
@@ -113,20 +134,15 @@ UNMAP_AFTER_INIT bool GraphicsManagement::determine_and_initialize_graphics_devi
             //  support, so we want to utilize the provided framebuffer of these
             //  devices, if possible.
             if (!m_vga_adapter && PCI::is_io_space_enabled(device_identifier.address())) {
-            if (multiboot_framebuffer_type == MULTIBOOT_FRAMEBUFFER_TYPE_RGB) {
-                dmesgln("Graphics: Using a preset resolution from the bootloader");
-                adapter = VGACompatibleAdapter::initialize_with_preset_resolution(device_identifier,
-                    multiboot_framebuffer_addr,
-                    multiboot_framebuffer_width,
-                    multiboot_framebuffer_height,
-                    multiboot_framebuffer_pitch);
-            }
+                create_bootloader_framebuffer_device();
             } else {
                 dmesgln("Graphics: Using a VGA compatible generic adapter");
                 adapter = VGACompatibleAdapter::initialize(device_identifier);
             }
             break;
         }
+    }
+
     if (!adapter)
         return false;
     add_and_configure_adapter(*adapter);
@@ -179,8 +195,10 @@ UNMAP_AFTER_INIT bool GraphicsManagement::initialize()
      * be created, so SystemServer will not try to initialize WindowServer.
      */
 
-    if (!framebuffer_devices_allowed())
-        dbgln("Forcing non-initialization of framebuffer devices");
+    if (framebuffer_devices_console_only())
+        dbgln("Forcing non-initialization of framebuffer devices (console only)");
+    else if (framebuffer_devices_use_bootloader_framebuffer())
+        dbgln("Forcing use of framebuffer set up by the bootloader");
 
     PCI::enumerate([&](PCI::DeviceIdentifier const& device_identifier) {
         // Note: Each graphics controller will try to set its native screen resolution

Kernel/Graphics/GraphicsManagement.h

@@ -36,7 +36,8 @@ public:
     unsigned allocate_minor_device_number() { return m_current_minor_number++; };
     GraphicsManagement();
 
-    bool framebuffer_devices_allowed() const;
+    bool framebuffer_devices_console_only() const;
+    bool framebuffer_devices_use_bootloader_framebuffer() const;
     bool framebuffer_devices_exist() const;
 
     Spinlock& main_vga_lock() { return m_main_vga_lock; }