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https://github.com/RGBCube/serenity
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Kernel: Implement serial port driver
This implements a basic 8250 UART serial port driver. It does not currently handle (or enable) interrupts, nor any runtime configuration.
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5 changed files with 244 additions and 0 deletions
110
Kernel/Devices/SerialDevice.cpp
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110
Kernel/Devices/SerialDevice.cpp
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#include <Kernel/Devices/SerialDevice.h>
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#include <Kernel/IO.h>
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SerialDevice::SerialDevice(int base_addr, unsigned minor)
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: CharacterDevice(4, minor)
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, m_base_addr(base_addr)
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{
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initialize();
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}
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SerialDevice::~SerialDevice()
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{
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}
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bool SerialDevice::can_read(FileDescription&) const
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{
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return (get_line_status() & DataReady) != 0;
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}
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ssize_t SerialDevice::read(FileDescription&, byte* buffer, ssize_t size)
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{
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if (!size)
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return 0;
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if (!(get_line_status() & DataReady))
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return 0;
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buffer[0] = IO::in8(m_base_addr);
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return 1;
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}
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bool SerialDevice::can_write(FileDescription&) const
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{
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return (get_line_status() & EmptyTransmitterHoldingRegister) != 0;
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}
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ssize_t SerialDevice::write(FileDescription&, const byte* buffer, ssize_t size)
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{
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if (!size)
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return 0;
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if (!(get_line_status() & EmptyTransmitterHoldingRegister))
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return 0;
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IO::out8(m_base_addr, buffer[0]);
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return 1;
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}
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void SerialDevice::initialize()
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{
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set_interrupts(0);
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set_baud(Baud38400);
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set_line_control(None, One, EightBits);
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set_fifo_control(EnableFIFO | ClearReceiveFIFO | ClearTransmitFIFO | TriggerLevel4);
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set_modem_control(RequestToSend | DataTerminalReady);
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}
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void SerialDevice::set_interrupts(char interrupt_enable)
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{
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m_interrupt_enable = interrupt_enable;
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IO::out8(m_base_addr + 1, interrupt_enable);
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}
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void SerialDevice::set_baud(Baud baud)
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{
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m_baud = baud;
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IO::out8(m_base_addr + 3, IO::in8(m_base_addr + 3) | 0x80); // turn on DLAB
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IO::out8(m_base_addr + 0, ((char)(baud)) >> 2); // lower half of divisor
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IO::out8(m_base_addr + 1, ((char)(baud)) & 0xff); // upper half of divisor
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IO::out8(m_base_addr + 3, IO::in8(m_base_addr + 3) & 0x7f); // turn off DLAB
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}
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void SerialDevice::set_fifo_control(char fifo_control)
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{
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m_fifo_control = fifo_control;
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IO::out8(m_base_addr + 2, fifo_control);
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}
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void SerialDevice::set_line_control(ParitySelect parity_select, StopBits stop_bits, WordLength word_length)
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{
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m_parity_select = parity_select;
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m_stop_bits = stop_bits;
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m_word_length = word_length;
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IO::out8(m_base_addr + 3, IO::in8(m_base_addr + 3) & (0xc0 | parity_select | stop_bits | word_length));
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}
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void SerialDevice::set_break_enable(bool break_enable)
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{
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m_break_enable = break_enable;
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IO::out8(m_base_addr + 3, IO::in8(m_base_addr + 3) & (break_enable ? 0xff : 0xbf));
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}
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void SerialDevice::set_modem_control(char modem_control)
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{
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m_modem_control = modem_control;
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IO::out8(m_base_addr + 4, modem_control);
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}
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char SerialDevice::get_line_status() const
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{
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return IO::in8(m_base_addr + 5);
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}
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120
Kernel/Devices/SerialDevice.h
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120
Kernel/Devices/SerialDevice.h
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#include <Kernel/Devices/CharacterDevice.h>
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#define SERIAL_COM1_ADDR 0x3F8
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#define SERIAL_COM2_ADDR 0x2F8
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#define SERIAL_COM3_ADDR 0x3E8
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#define SERIAL_COM4_ADDR 0x2E8
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class SerialDevice final : public CharacterDevice {
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AK_MAKE_ETERNAL
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public:
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SerialDevice(int base_addr, unsigned minor);
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virtual ~SerialDevice() override;
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// ^CharacterDevice
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virtual bool can_read(FileDescription&) const override;
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virtual ssize_t read(FileDescription&, byte*, ssize_t) override;
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virtual bool can_write(FileDescription&) const override;
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virtual ssize_t write(FileDescription&, const byte*, ssize_t) override;
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enum InterruptEnable {
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LowPowerMode = 0x01 << 5,
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SleepMode = 0x01 << 4,
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ModemStatusInterrupt = 0x01 << 3,
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ReceiverLineStatusInterrupt = 0x01 << 2,
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TransmitterHoldingRegisterEmptyInterrupt = 0x01 << 1,
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ReceivedDataAvailableInterrupt = 0x01 << 0
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};
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enum Baud {
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Baud50 = 2304,
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Baud110 = 1047,
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Baud220 = 524,
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Baud300 = 384,
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Baud600 = 192,
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Baud1200 = 96,
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Baud2400 = 48,
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Baud4800 = 24,
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Baud9600 = 12,
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Baud19200 = 6,
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Baud38400 = 3,
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Baud57600 = 2,
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Baud115200 = 1
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};
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enum ParitySelect {
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None = 0x00 << 3,
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Odd = 0x01 << 3,
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Even = 0x03 << 3,
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Mark = 0x05 << 3,
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Space = 0x07 << 3
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};
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enum StopBits {
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One = 0x00 << 2,
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Two = 0x01 << 2
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};
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enum WordLength {
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FiveBits = 0x00,
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SixBits = 0x01,
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SevenBits = 0x02,
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EightBits = 0x03
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};
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enum FIFOControl {
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EnableFIFO = 0x01 << 0,
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ClearReceiveFIFO = 0x01 << 1,
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ClearTransmitFIFO = 0x01 << 2,
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Enable64ByteFIFO = 0x01 << 5,
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TriggerLevel1 = 0x00 << 6,
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TriggerLevel2 = 0x01 << 6,
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TriggerLevel3 = 0x02 << 6,
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TriggerLevel4 = 0x03 << 6
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};
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enum ModemControl {
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AutoflowControlEnabled = 0x01 << 5,
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LoopbackMode = 0x01 << 4,
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AuxiliaryOutput2 = 0x01 << 3,
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AuxiliaryOutput1 = 0x01 << 2,
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RequestToSend = 0x01 << 1,
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DataTerminalReady = 0x01 << 0
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};
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enum LineStatus {
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ErrorInReceivedFIFO = 0x01 << 7,
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EmptyDataHoldingRegisters = 0x01 << 6,
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EmptyTransmitterHoldingRegister = 0x01 << 5,
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BreakInterrupt = 0x01 << 4,
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FramingError = 0x01 << 3,
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ParityError = 0x01 << 2,
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OverrunError = 0x01 << 1,
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DataReady = 0x01 << 0
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};
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private:
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// ^CharacterDevice
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virtual const char* class_name() const override { return "SerialDevice"; }
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void initialize();
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void set_interrupts(char interrupt_enable);
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void set_baud(Baud);
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void set_fifo_control(char fifo_control);
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void set_line_control(ParitySelect, StopBits, WordLength);
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void set_break_enable(bool break_enable);
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void set_modem_control(char modem_control);
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char get_line_status() const;
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bool rx_ready();
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bool tx_ready();
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int m_base_addr;
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char m_interrupt_enable;
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char m_fifo_control;
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Baud m_baud;
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ParitySelect m_parity_select;
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StopBits m_stop_bits;
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WordLength m_word_length;
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bool m_break_enable;
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char m_modem_control;
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};
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