Kernel: Make File's can_read/can_write take a const FileDescription&

Asking a File if we could possibly read or write it will never mutate
the asking FileDescription&, so it should be const.

Kernel/Devices/BXVGADevice.cpp

@@ -150,12 +150,12 @@ int BXVGADevice::ioctl(FileDescription&, unsigned request, unsigned arg)
     };
 }
 
-bool BXVGADevice::can_read(FileDescription&) const
+bool BXVGADevice::can_read(const FileDescription&) const
 {
     ASSERT_NOT_REACHED();
 }
 
-bool BXVGADevice::can_write(FileDescription&) const
+bool BXVGADevice::can_write(const FileDescription&) const
 {
     ASSERT_NOT_REACHED();
 }

Kernel/Devices/BXVGADevice.h

@@ -17,8 +17,8 @@ public:
 
 private:
     virtual const char* class_name() const override { return "BXVGA"; }
-    virtual bool can_read(FileDescription&) const override;
-    virtual bool can_write(FileDescription&) const override;
+    virtual bool can_read(const FileDescription&) const override;
+    virtual bool can_write(const FileDescription&) const override;
     virtual ssize_t read(FileDescription&, u8*, ssize_t) override;
     virtual ssize_t write(FileDescription&, const u8*, ssize_t) override;
 

Kernel/Devices/DebugLogDevice.h

@@ -11,7 +11,7 @@ private:
     // ^CharacterDevice
     virtual ssize_t read(FileDescription&, u8*, ssize_t) override { return 0; }
     virtual ssize_t write(FileDescription&, const u8*, ssize_t) override;
-    virtual bool can_write(FileDescription&) const override { return true; }
-    virtual bool can_read(FileDescription&) const override { return true; }
+    virtual bool can_write(const FileDescription&) const override { return true; }
+    virtual bool can_read(const FileDescription&) const override { return true; }
     virtual const char* class_name() const override { return "DebugLogDevice"; }
 };

Kernel/Devices/DiskPartition.h

@@ -15,9 +15,9 @@ public:
 
     // ^BlockDevice
     virtual ssize_t read(FileDescription&, u8*, ssize_t) override { return 0; }
-    virtual bool can_read(FileDescription&) const override { return true; }
+    virtual bool can_read(const FileDescription&) const override { return true; }
     virtual ssize_t write(FileDescription&, const u8*, ssize_t) override { return 0; }
-    virtual bool can_write(FileDescription&) const override { return true; }
+    virtual bool can_write(const FileDescription&) const override { return true; }
 
 private:
     virtual const char* class_name() const override;

Kernel/Devices/FloppyDiskDevice.h

@@ -143,9 +143,9 @@ public:
 
     // ^BlockDevice
     virtual ssize_t read(FileDescription&, u8*, ssize_t) override { return 0; }
-    virtual bool can_read(FileDescription&) const override { return true; }
+    virtual bool can_read(const FileDescription&) const override { return true; }
     virtual ssize_t write(FileDescription&, const u8*, ssize_t) override { return 0; }
-    virtual bool can_write(FileDescription&) const override { return true; }
+    virtual bool can_write(const FileDescription&) const override { return true; }
 
 protected:
     explicit FloppyDiskDevice(DriveType);

Kernel/Devices/FullDevice.cpp

@@ -12,7 +12,7 @@ FullDevice::~FullDevice()
 {
 }
 
-bool FullDevice::can_read(FileDescription&) const
+bool FullDevice::can_read(const FileDescription&) const
 {
     return true;
 }

Kernel/Devices/FullDevice.h

@@ -12,7 +12,7 @@ private:
     // ^CharacterDevice
     virtual ssize_t read(FileDescription&, u8*, ssize_t) override;
     virtual ssize_t write(FileDescription&, const u8*, ssize_t) override;
-    virtual bool can_read(FileDescription&) const override;
-    virtual bool can_write(FileDescription&) const override { return true; }
+    virtual bool can_read(const FileDescription&) const override;
+    virtual bool can_write(const FileDescription&) const override { return true; }
     virtual const char* class_name() const override { return "FullDevice"; }
 };

Kernel/Devices/KeyboardDevice.cpp

@@ -368,7 +368,7 @@ KeyboardDevice::~KeyboardDevice()
 {
 }
 
-bool KeyboardDevice::can_read(FileDescription&) const
+bool KeyboardDevice::can_read(const FileDescription&) const
 {
     return !m_queue.is_empty();
 }

Kernel/Devices/KeyboardDevice.h

@@ -24,9 +24,9 @@ public:
 
     // ^CharacterDevice
     virtual ssize_t read(FileDescription&, u8* buffer, ssize_t) override;
-    virtual bool can_read(FileDescription&) const override;
+    virtual bool can_read(const FileDescription&) const override;
     virtual ssize_t write(FileDescription&, const u8* buffer, ssize_t) override;
-    virtual bool can_write(FileDescription&) const override { return true; }
+    virtual bool can_write(const FileDescription&) const override { return true; }
 
 private:
     // ^IRQHandler

Kernel/Devices/MBVGADevice.cpp

@@ -82,12 +82,12 @@ int MBVGADevice::ioctl(FileDescription&, unsigned request, unsigned arg)
     };
 }
 
-bool MBVGADevice::can_read(FileDescription&) const
+bool MBVGADevice::can_read(const FileDescription&) const
 {
     ASSERT_NOT_REACHED();
 }
 
-bool MBVGADevice::can_write(FileDescription&) const
+bool MBVGADevice::can_write(const FileDescription&) const
 {
     ASSERT_NOT_REACHED();
 }

Kernel/Devices/MBVGADevice.h

@@ -17,8 +17,8 @@ public:
 
 private:
     virtual const char* class_name() const override { return "MBVGA"; }
-    virtual bool can_read(FileDescription&) const override;
-    virtual bool can_write(FileDescription&) const override;
+    virtual bool can_read(const FileDescription&) const override;
+    virtual bool can_write(const FileDescription&) const override;
     virtual ssize_t read(FileDescription&, u8*, ssize_t) override;
     virtual ssize_t write(FileDescription&, const u8*, ssize_t) override;
 

Kernel/Devices/NullDevice.cpp

@@ -20,7 +20,7 @@ NullDevice::~NullDevice()
 {
 }
 
-bool NullDevice::can_read(FileDescription&) const
+bool NullDevice::can_read(const FileDescription&) const
 {
     return true;
 }

Kernel/Devices/NullDevice.h

@@ -14,7 +14,7 @@ private:
     // ^CharacterDevice
     virtual ssize_t read(FileDescription&, u8*, ssize_t) override;
     virtual ssize_t write(FileDescription&, const u8*, ssize_t) override;
-    virtual bool can_write(FileDescription&) const override { return true; }
-    virtual bool can_read(FileDescription&) const override;
+    virtual bool can_write(const FileDescription&) const override { return true; }
+    virtual bool can_read(const FileDescription&) const override;
     virtual const char* class_name() const override { return "NullDevice"; }
 };

Kernel/Devices/PATADiskDevice.h

@@ -36,9 +36,9 @@ public:
 
     // ^BlockDevice
     virtual ssize_t read(FileDescription&, u8*, ssize_t) override { return 0; }
-    virtual bool can_read(FileDescription&) const override { return true; }
+    virtual bool can_read(const FileDescription&) const override { return true; }
     virtual ssize_t write(FileDescription&, const u8*, ssize_t) override { return 0; }
-    virtual bool can_write(FileDescription&) const override { return true; }
+    virtual bool can_write(const FileDescription&) const override { return true; }
 
 protected:
     explicit PATADiskDevice(PATAChannel&, DriveType, int, int);

Kernel/Devices/PS2MouseDevice.cpp

@@ -255,7 +255,7 @@ u8 PS2MouseDevice::mouse_read()
     return IO::in8(I8042_BUFFER);
 }
 
-bool PS2MouseDevice::can_read(FileDescription&) const
+bool PS2MouseDevice::can_read(const FileDescription&) const
 {
     return !m_queue.is_empty();
 }

Kernel/Devices/PS2MouseDevice.h

@@ -14,10 +14,10 @@ public:
     static PS2MouseDevice& the();
 
     // ^CharacterDevice
-    virtual bool can_read(FileDescription&) const override;
+    virtual bool can_read(const FileDescription&) const override;
     virtual ssize_t read(FileDescription&, u8*, ssize_t) override;
     virtual ssize_t write(FileDescription&, const u8*, ssize_t) override;
-    virtual bool can_write(FileDescription&) const override { return true; }
+    virtual bool can_write(const FileDescription&) const override { return true; }
 
 private:
     // ^IRQHandler

Kernel/Devices/RandomDevice.cpp

@@ -26,7 +26,7 @@ static void mysrand(unsigned seed)
 }
 #endif
 
-bool RandomDevice::can_read(FileDescription&) const
+bool RandomDevice::can_read(const FileDescription&) const
 {
     return true;
 }

Kernel/Devices/RandomDevice.h

@@ -14,7 +14,7 @@ private:
     // ^CharacterDevice
     virtual ssize_t read(FileDescription&, u8*, ssize_t) override;
     virtual ssize_t write(FileDescription&, const u8*, ssize_t) override;
-    virtual bool can_read(FileDescription&) const override;
-    virtual bool can_write(FileDescription&) const override { return true; }
+    virtual bool can_read(const FileDescription&) const override;
+    virtual bool can_write(const FileDescription&) const override { return true; }
     virtual const char* class_name() const override { return "RandomDevice"; }
 };

Kernel/Devices/SB16.cpp

@@ -84,7 +84,7 @@ void SB16::initialize()
     enable_irq();
 }
 
-bool SB16::can_read(FileDescription&) const
+bool SB16::can_read(const FileDescription&) const
 {
     return false;
 }

Kernel/Devices/SB16.h

@@ -17,10 +17,10 @@ public:
     static SB16& the();
 
     // ^CharacterDevice
-    virtual bool can_read(FileDescription&) const override;
+    virtual bool can_read(const FileDescription&) const override;
     virtual ssize_t read(FileDescription&, u8*, ssize_t) override;
     virtual ssize_t write(FileDescription&, const u8*, ssize_t) override;
-    virtual bool can_write(FileDescription&) const override { return true; }
+    virtual bool can_write(const FileDescription&) const override { return true; }
 
 private:
     // ^IRQHandler

Kernel/Devices/SerialDevice.cpp

@@ -12,7 +12,7 @@ SerialDevice::~SerialDevice()
 {
 }
 
-bool SerialDevice::can_read(FileDescription&) const
+bool SerialDevice::can_read(const FileDescription&) const
 {
     return (get_line_status() & DataReady) != 0;
 }
@@ -30,7 +30,7 @@ ssize_t SerialDevice::read(FileDescription&, u8* buffer, ssize_t size)
     return 1;
 }
 
-bool SerialDevice::can_write(FileDescription&) const
+bool SerialDevice::can_write(const FileDescription&) const
 {
     return (get_line_status() & EmptyTransmitterHoldingRegister) != 0;
 }

Kernel/Devices/SerialDevice.h

@@ -12,9 +12,9 @@ public:
     virtual ~SerialDevice() override;
 
     // ^CharacterDevice
-    virtual bool can_read(FileDescription&) const override;
+    virtual bool can_read(const FileDescription&) const override;
     virtual ssize_t read(FileDescription&, u8*, ssize_t) override;
-    virtual bool can_write(FileDescription&) const override;
+    virtual bool can_write(const FileDescription&) const override;
     virtual ssize_t write(FileDescription&, const u8*, ssize_t) override;
 
     enum InterruptEnable {

Kernel/Devices/ZeroDevice.cpp

@@ -11,7 +11,7 @@ ZeroDevice::~ZeroDevice()
 {
 }
 
-bool ZeroDevice::can_read(FileDescription&) const
+bool ZeroDevice::can_read(const FileDescription&) const
 {
     return true;
 }

Kernel/Devices/ZeroDevice.h

@@ -12,7 +12,7 @@ private:
     // ^CharacterDevice
     virtual ssize_t read(FileDescription&, u8*, ssize_t) override;
     virtual ssize_t write(FileDescription&, const u8*, ssize_t) override;
-    virtual bool can_read(FileDescription&) const override;
-    virtual bool can_write(FileDescription&) const override { return true; }
+    virtual bool can_read(const FileDescription&) const override;
+    virtual bool can_write(const FileDescription&) const override { return true; }
     virtual const char* class_name() const override { return "ZeroDevice"; }
 };