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Kernel: Implement variable rate audio support for AC97 devices

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Previously we `VERIFY()`ed that the device supports variable-rate audio
(VRA). Now, we query the VRA bit and if VRA is not supported, we do not
enable double-rate audio and disallow setting any sample rate except
the fixed 48kHz rate as defined by the AC'97 specification. This should
allow the driver to function on a wider array of hardware.

Note that in the AC'97 specification, DRA without VRA is allowed when
supported: this effectively doubles the sample rate to 96kHZ. For now,
we ignore that possibility and let it default to 48kHZ.
This commit is contained in:
Jelle Raaijmakers 2021-11-25 19:37:11 +01:00 • committed by Andreas Kling
parent 377a984905
commit 58bcb93777
2 changed files with 23 additions and 11 deletions
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4
Kernel/Devices/Audio/AC97.h
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@ -54,6 +54,7 @@ private:
};
enum ExtendedAudioStatusControlFlag : u16 {
VariableRateAudio = 1 << 0,
DoubleRateAudio = 1 << 1,
};
@ -170,7 +171,8 @@ private:
u8 m_output_buffer_page_count = 4;
u8 m_output_buffer_page_index = 0;
AC97Channel m_pcm_out_channel;
u32 m_sample_rate = 44100;
u32 m_sample_rate = 0;
bool m_variable_rate_pcm_supported = false;
};
}