Kernel: Make device generate their own names

Besides removing the monolithic DevFSDeviceInode::determine_name()
method, being able to determine a device's name inside the /dev
hierarchy outside of DevFS has its uses.

Kernel/Devices/BXVGADevice.cpp

@@ -192,6 +192,11 @@ KResultOr<Region*> BXVGADevice::mmap(Process& process, FileDescription&, Virtual
         shared);
 }
 
+String BXVGADevice::device_name() const
+{
+    return String::formatted("fb{}", minor());
+}
+
 int BXVGADevice::ioctl(FileDescription&, unsigned request, FlatPtr arg)
 {
     REQUIRE_PROMISE(video);

Kernel/Devices/BXVGADevice.h

@@ -46,6 +46,7 @@ public:
 
     // ^Device
     virtual mode_t required_mode() const override { return 0660; }
+    virtual String device_name() const override;
 
 private:
     virtual const char* class_name() const override { return "BXVGA"; }

Kernel/Devices/Device.h

@@ -58,6 +58,7 @@ public:
     uid_t gid() const { return m_gid; }
 
     virtual mode_t required_mode() const = 0;
+    virtual String device_name() const = 0;
 
     virtual bool is_device() const override { return true; }
     virtual bool is_disk_device() const { return false; }

Kernel/Devices/FullDevice.h

@@ -38,6 +38,7 @@ public:
 
     // ^Device
     virtual mode_t required_mode() const override { return 0600; }
+    virtual String device_name() const override { return "full"; }
 
 private:
     // ^CharacterDevice

Kernel/Devices/KeyboardDevice.h

@@ -76,6 +76,7 @@ public:
 
     // ^Device
     virtual mode_t required_mode() const override { return 0440; }
+    virtual String device_name() const override { return "keyboard"; }
 
 private:
     // ^IRQHandler

Kernel/Devices/MBVGADevice.cpp

@@ -114,4 +114,9 @@ int MBVGADevice::ioctl(FileDescription&, unsigned request, FlatPtr arg)
     };
 }
 
+String MBVGADevice::device_name() const
+{
+    return String::formatted("fb{}", minor());
+}
+
 }

Kernel/Devices/MBVGADevice.h

@@ -45,6 +45,7 @@ public:
 
     // ^Device
     virtual mode_t required_mode() const override { return 0660; }
+    virtual String device_name() const override;
 
 private:
     virtual const char* class_name() const override { return "MBVGA"; }

Kernel/Devices/NullDevice.h

@@ -41,6 +41,7 @@ public:
 
     // ^Device
     virtual mode_t required_mode() const override { return 0666; }
+    virtual String device_name() const override { return "null"; }
 
 private:
     // ^CharacterDevice

Kernel/Devices/PS2MouseDevice.h

@@ -63,6 +63,7 @@ public:
 
     // ^Device
     virtual mode_t required_mode() const override { return 0440; }
+    virtual String device_name() const override { return "mouse"; }
 
 private:
     // ^IRQHandler

Kernel/Devices/RandomDevice.h

@@ -38,6 +38,7 @@ public:
 
     // ^Device
     virtual mode_t required_mode() const override { return 0666; }
+    virtual String device_name() const override { return "random"; }
 
 private:
     // ^CharacterDevice

Kernel/Devices/SB16.h

@@ -55,6 +55,7 @@ public:
 
     // ^Device
     virtual mode_t required_mode() const override { return 0220; }
+    virtual String device_name() const override { return "audio"; }
 
 private:
     // ^IRQHandler

Kernel/Devices/SerialDevice.cpp

@@ -87,6 +87,11 @@ KResultOr<size_t> SerialDevice::write(FileDescription&, size_t, const UserOrKern
     return (size_t)nread;
 }
 
+String SerialDevice::device_name() const
+{
+    return String::formatted("ttyS{}", minor() - 64);
+}
+
 void SerialDevice::initialize()
 {
     set_interrupts(0);

Kernel/Devices/SerialDevice.h

@@ -125,6 +125,7 @@ public:
 
     // ^Device
     virtual mode_t required_mode() const override { return 0620; }
+    virtual String device_name() const override;
 
 private:
     // ^CharacterDevice

Kernel/Devices/ZeroDevice.h

@@ -38,6 +38,7 @@ public:
 
     // ^Device
     virtual mode_t required_mode() const override { return 0666; }
+    virtual String device_name() const override { return "zero"; }
 
 private:
     // ^CharacterDevice