Kernel: Make /proc/PID/fds display something useful for character devices.

Kernel/Console.h

@@ -18,10 +18,12 @@ public:
     Console();
     virtual ~Console() override;
 
+    // ^CharacterDevice
     virtual bool can_read(Process&) const override;
     virtual bool can_write(Process&) const override { return true; }
     virtual ssize_t read(Process&, byte* buffer, size_t size) override;
     virtual ssize_t write(Process&, const byte* data, size_t size) override;
+    virtual const char* class_name() const override { return "Console"; }
 
     void setImplementation(ConsoleImplementation* implementation) { m_implementation = implementation; }
 

Kernel/GUIEventDevice.h

@@ -13,4 +13,5 @@ private:
     virtual ssize_t write(Process&, const byte* buffer, size_t bufferSize) override;
     virtual bool can_read(Process&) const override;
     virtual bool can_write(Process&) const override { return true; }
+    virtual const char* class_name() const override { return "GUIEventDevice"; }
 };

Kernel/Keyboard.h

@@ -42,6 +42,9 @@ private:
     // ^IRQHandler
     virtual void handle_irq() override;
 
+    // ^CharacterDevice
+    virtual const char* class_name() const override { return "Keyboard"; }
+
     void emit(byte);
 
     KeyboardClient* m_client { nullptr };

Kernel/MasterPTY.h

@@ -10,6 +10,7 @@ public:
     explicit MasterPTY(unsigned index);
     virtual ~MasterPTY() override;
 
+    // ^CharacterDevice
     virtual ssize_t read(Process&, byte*, size_t) override;
     virtual ssize_t write(Process&, const byte*, size_t) override;
     virtual bool can_read(Process&) const override;
@@ -21,6 +22,9 @@ public:
     void on_slave_write(const byte*, size_t);
 
 private:
+    // ^CharacterDevice
+    virtual const char* class_name() const override { return "MasterPTY"; }
+
     SlavePTY& m_slave;
     unsigned m_index;
     DoubleBuffer m_buffer;

Kernel/PS2MouseDevice.h

@@ -20,6 +20,9 @@ private:
     // ^IRQHandler
     virtual void handle_irq() override;
 
+    // ^CharacterDevice
+    virtual const char* class_name() const override { return "PS2MouseDevice"; }
+
     void initialize();
     void prepare_for_input();
     void prepare_for_output();

Kernel/PTYMultiplexer.h

@@ -19,6 +19,9 @@ public:
     virtual bool can_write(Process&) const override { return true; }
 
 private:
+    // ^CharacterDevice
+    virtual const char* class_name() const override { return "PTYMultiplexer"; }
+
     Lock m_lock;
     Vector<RetainPtr<MasterPTY>> m_freelist;
 };

Kernel/SlavePTY.h

@@ -8,16 +8,18 @@ class SlavePTY final : public TTY {
 public:
     virtual ~SlavePTY() override;
 
-    virtual String tty_name() const override;
-
     void on_master_write(const byte*, size_t);
     unsigned index() const { return m_index; }
 
-protected:
-    virtual void on_tty_write(const byte*, size_t) override;
-    virtual bool can_write(Process&) const override;
-
 private:
+    // ^TTY
+    virtual String tty_name() const override;
+    virtual void on_tty_write(const byte*, size_t) override;
+
+    // ^CharacterDevice
+    virtual bool can_write(Process&) const override;
+    virtual const char* class_name() const override { return "SlavePTY"; }
+
     friend class MasterPTY;
     SlavePTY(MasterPTY&, unsigned index);
 

Kernel/VirtualConsole.h

@@ -26,6 +26,9 @@ private:
     virtual void on_tty_write(const byte*, size_t) override;
     virtual String tty_name() const override;
 
+    // ^CharacterDevice
+    virtual const char* class_name() const override { return "VirtualConsole"; }
+
     void set_active(bool);
     void on_char(byte);
 

VirtualFileSystem/CharacterDevice.h

@@ -29,6 +29,8 @@ public:
 
     virtual int ioctl(Process&, unsigned request, unsigned arg);
 
+    virtual const char* class_name() const = 0;
+
 protected:
     CharacterDevice(unsigned major, unsigned minor) : m_major(major), m_minor(minor) { }
 

VirtualFileSystem/FileDescriptor.cpp

@@ -297,6 +297,11 @@ String FileDescriptor::absolute_path()
         ksprintf(buf, "fifo:%x", m_fifo.ptr());
         return buf;
     }
+    if (is_character_device()) {
+        char buf[128];
+        ksprintf(buf, "device:%u,%u (%s)", m_device->major(), m_device->minor(), m_device->class_name());
+        return buf;
+    }
     ASSERT(m_inode);
     return VFS::the().absolute_path(*m_inode);
 }

VirtualFileSystem/FullDevice.h

@@ -8,9 +8,12 @@ public:
     FullDevice();
     virtual ~FullDevice() override;
 
+private:
+    // ^CharacterDevice
     virtual ssize_t read(Process&, byte* buffer, size_t bufferSize) override;
     virtual ssize_t write(Process&, const byte* buffer, size_t bufferSize) override;
     virtual bool can_read(Process&) const override;
     virtual bool can_write(Process&) const override { return true; }
+    virtual const char* class_name() const override { return "FullDevice"; }
 };
 

VirtualFileSystem/NullDevice.h

@@ -8,9 +8,12 @@ public:
     NullDevice();
     virtual ~NullDevice() override;
 
+private:
+    // ^CharacterDevice
     virtual ssize_t read(Process&, byte* buffer, size_t bufferSize) override;
     virtual ssize_t write(Process&, const byte* buffer, size_t bufferSize) override;
     virtual bool can_write(Process&) const override { return true; }
     virtual bool can_read(Process&) const override;
+    virtual const char* class_name() const override { return "CharacterDevice"; }
 };
 

VirtualFileSystem/RandomDevice.h

@@ -8,9 +8,12 @@ public:
     RandomDevice();
     virtual ~RandomDevice() override;
 
+private:
+    // ^CharacterDevice
     virtual ssize_t read(Process&, byte* buffer, size_t bufferSize) override;
     virtual ssize_t write(Process&, const byte* buffer, size_t bufferSize) override;
     virtual bool can_read(Process&) const override;
     virtual bool can_write(Process&) const override { return true; }
+    virtual const char* class_name() const override { return "RandomDevice"; }
 };
 

VirtualFileSystem/ZeroDevice.h

@@ -8,9 +8,12 @@ public:
     ZeroDevice();
     virtual ~ZeroDevice() override;
 
+private:
+    // ^CharacterDevice
     virtual ssize_t read(Process&, byte* buffer, size_t bufferSize) override;
     virtual ssize_t write(Process&, const byte* buffer, size_t bufferSize) override;
     virtual bool can_read(Process&) const override;
     virtual bool can_write(Process&) const override { return true; }
+    virtual const char* class_name() const override { return "ZeroDevice"; }
 };