69 lines
2.0 KiB
C
Executable File
69 lines
2.0 KiB
C
Executable File
#include "devices/speaker.h"
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#include "devices/pit.h"
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#include "threads/io.h"
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#include "threads/interrupt.h"
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#include "devices/timer.h"
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/* Speaker port enable I/O register. */
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#define SPEAKER_PORT_GATE 0x61
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/* Speaker port enable bits. */
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#define SPEAKER_GATE_ENABLE 0x03
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/* Sets the PC speaker to emit a tone at the given FREQUENCY, in
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Hz. */
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void
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speaker_on (int frequency)
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{
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if (frequency >= 20 && frequency <= 20000)
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{
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/* Set the timer channel that's connected to the speaker to
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output a square wave at the given FREQUENCY, then
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connect the timer channel output to the speaker. */
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enum intr_level old_level = intr_disable ();
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pit_configure_channel (2, 3, frequency);
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outb (SPEAKER_PORT_GATE, inb (SPEAKER_PORT_GATE) | SPEAKER_GATE_ENABLE);
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intr_set_level (old_level);
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}
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else
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{
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/* FREQUENCY is outside the range of normal human hearing.
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Just turn off the speaker. */
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speaker_off ();
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}
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}
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/* Turn off the PC speaker, by disconnecting the timer channel's
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output from the speaker. */
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void
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speaker_off (void)
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{
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enum intr_level old_level = intr_disable ();
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outb (SPEAKER_PORT_GATE, inb (SPEAKER_PORT_GATE) & ~SPEAKER_GATE_ENABLE);
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intr_set_level (old_level);
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}
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/* Briefly beep the PC speaker. */
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void
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speaker_beep (void)
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{
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/* Only attempt to beep the speaker if interrupts are enabled,
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because we don't want to freeze the machine during the beep.
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We could add a hook to the timer interrupt to avoid that
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problem, but then we'd risk failing to ever stop the beep if
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Pintos crashes for some unrelated reason. There's nothing
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more annoying than a machine whose beeping you can't stop
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without a power cycle.
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We can't just enable interrupts while we sleep. For one
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thing, we get called (indirectly) from printf, which should
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always work, even during boot before we're ready to enable
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interrupts. */
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if (intr_get_level () == INTR_ON)
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{
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speaker_on (440);
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timer_msleep (250);
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speaker_off ();
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}
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}
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