jcs.org
Serenity Operating System
1/*
2 * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
3 * Copyright (c) 2021, Idan Horowitz <idan.horowitz@serenityos.org>
4 *
5 * SPDX-License-Identifier: BSD-2-Clause
6 */
7
8#include <Kernel/Devices/DeviceManagement.h>
9#include <Kernel/Devices/SerialDevice.h>
10#include <Kernel/IOWindow.h>
11#include <Kernel/Sections.h>
12
13namespace Kernel {
14
15UNMAP_AFTER_INIT SerialDevice::SerialDevice(NonnullOwnPtr<IOWindow> registers_io_window, unsigned minor)
16 : CharacterDevice(4, minor)
17 , m_registers_io_window(move(registers_io_window))
18{
19 initialize();
20}
21
22UNMAP_AFTER_INIT SerialDevice::~SerialDevice() = default;
23
24bool SerialDevice::can_read(OpenFileDescription const&, u64) const
25{
26 return (get_line_status() & DataReady) != 0;
27}
28
29ErrorOr<size_t> SerialDevice::read(OpenFileDescription&, u64, UserOrKernelBuffer& buffer, size_t size)
30{
31 if (!size)
32 return 0;
33
34 SpinlockLocker lock(m_serial_lock);
35 if (!(get_line_status() & DataReady))
36 return 0;
37
38 return buffer.write_buffered<128>(size, [&](Bytes bytes) {
39 for (auto& byte : bytes)
40 byte = m_registers_io_window->read8(0);
41 return bytes.size();
42 });
43}
44
45bool SerialDevice::can_write(OpenFileDescription const&, u64) const
46{
47 return (get_line_status() & EmptyTransmitterHoldingRegister) != 0;
48}
49
50ErrorOr<size_t> SerialDevice::write(OpenFileDescription& description, u64, UserOrKernelBuffer const& buffer, size_t size)
51{
52 if (!size)
53 return 0;
54
55 SpinlockLocker lock(m_serial_lock);
56 if (!can_write(description, size))
57 return EAGAIN;
58
59 return buffer.read_buffered<128>(size, [&](ReadonlyBytes bytes) {
60 for (const auto& byte : bytes)
61 put_char(byte);
62 return bytes.size();
63 });
64}
65
66void SerialDevice::put_char(char ch)
67{
68 while ((get_line_status() & EmptyTransmitterHoldingRegister) == 0)
69 ;
70
71 if (ch == '\n' && !m_last_put_char_was_carriage_return)
72 m_registers_io_window->write8(0, '\r');
73
74 m_registers_io_window->write8(0, ch);
75
76 m_last_put_char_was_carriage_return = (ch == '\r');
77}
78
79UNMAP_AFTER_INIT void SerialDevice::initialize()
80{
81 set_interrupts(false);
82 set_baud(Baud38400);
83 set_line_control(None, One, EightBits);
84 set_fifo_control(EnableFIFO | ClearReceiveFIFO | ClearTransmitFIFO | TriggerLevel4);
85 set_modem_control(RequestToSend | DataTerminalReady);
86}
87
88UNMAP_AFTER_INIT void SerialDevice::set_interrupts(bool interrupt_enable)
89{
90 m_interrupt_enable = interrupt_enable;
91
92 m_registers_io_window->write8(1, interrupt_enable);
93}
94
95void SerialDevice::set_baud(Baud baud)
96{
97 m_baud = baud;
98
99 m_registers_io_window->write8(3, m_registers_io_window->read8(3) | 0x80); // turn on DLAB
100 m_registers_io_window->write8(0, ((u8)(baud)) & 0xff); // lower half of divisor
101 m_registers_io_window->write8(1, ((u8)(baud)) >> 2); // lower half of divisor
102 m_registers_io_window->write8(3, m_registers_io_window->read8(3) & 0x7f); // turn off DLAB
103}
104
105void SerialDevice::set_fifo_control(u8 fifo_control)
106{
107 m_fifo_control = fifo_control;
108 m_registers_io_window->write8(2, fifo_control);
109}
110
111void SerialDevice::set_line_control(ParitySelect parity_select, StopBits stop_bits, WordLength word_length)
112{
113 m_parity_select = parity_select;
114 m_stop_bits = stop_bits;
115 m_word_length = word_length;
116
117 m_registers_io_window->write8(3, (m_registers_io_window->read8(3) & ~0x3f) | parity_select | stop_bits | word_length);
118}
119
120void SerialDevice::set_break_enable(bool break_enable)
121{
122 m_break_enable = break_enable;
123
124 m_registers_io_window->write8(3, m_registers_io_window->read8(3) & (break_enable ? 0xff : 0xbf));
125}
126
127void SerialDevice::set_modem_control(u8 modem_control)
128{
129 m_modem_control = modem_control;
130
131 m_registers_io_window->write8(4, modem_control);
132}
133
134u8 SerialDevice::get_line_status() const
135{
136 return m_registers_io_window->read8(5);
137}
138
139}