53 lines
1.6 KiB
C
53 lines
1.6 KiB
C
/*
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Copyright 2022 Mattia Giambirtone & Contributors
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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// Utilities for writing to and reading from I/O ports
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#include "kernel/drivers/ports/ports.h"
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// Note: We use the volatile modifier everywhere because
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// the compiler might try and optimize some of our code
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// away, since its effects are not directly visible from
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// the code itself, which would be a nightmare to debug!
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byte readByte(u16 port) {
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// Reads a byte from the specified I/O port
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volatile byte result;
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asm volatile ("in %%dx, %%al" : "=a" (result) : "d" (port));
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return result;
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}
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void writeByte(u16 port, byte data) {
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// Writes a byte to the specified I/O port
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asm volatile ("out %%al, %%dx" : : "a" (data), "d" (port));
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}
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u16 readWord(u16 port) {
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// Reads a word (16 bits) from the specified I/O port
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volatile u16 result;
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asm volatile ("in %%dx, %%ax" : "=a" (result) : "d" (port));
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return result;
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}
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void writeWord(u16 port, u16 data) {
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// Writes a word (16 bits) to the specified I/O port
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asm volatile ("out %%ax, %%dx" : : "a" (data), "d" (port));
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} |