Ideally, we would want the audio controller to run a channel at a
device's initial sample rate instead of hardcoding 44.1 KHz. However,
most audio is provided at 44.1 KHz and as long as `Audio::Resampler`
introduces significant audio artifacts, let's set a sensible sample
rate that offers a better experience for most users.
This can be removed after someone implements a higher quality
`Audio::Resampler`.
While doing this, we can also just return a normal RefPtr instead of a
LockRefPtr, because we create these channels when initializing an audio
controller, and never change the pointer in AudioController instances
after their initialization, hence no locking is necessary.
This header has always been fundamentally a Kernel API file. Move it
where it belongs. Include it directly in Kernel files, and make
Userland applications include it via sys/ioctl.h rather than directly.
Until now, our kernel has reimplemented a number of AK classes to
provide automatic internal locking:
- RefPtr
- NonnullRefPtr
- WeakPtr
- Weakable
This patch renames the Kernel classes so that they can coexist with
the original AK classes:
- RefPtr => LockRefPtr
- NonnullRefPtr => NonnullLockRefPtr
- WeakPtr => LockWeakPtr
- Weakable => LockWeakable
The goal here is to eventually get rid of the Lock* classes in favor of
using external locking.
We have 3 new components:
1. The AudioManagement singleton. This class like in other subsystems,
is responsible to find hardware audio controllers and keep a reference
to them.
2. AudioController class - this class is the parent class for hardware
controllers like the Sound Blaster 16 or Intel 82801AA (AC97). For now,
this class has simple interface for getting and controlling sample rate
of audio channels, as well a write interface for specific audio channel
but not reading from it. One AudioController object might have multiple
AudioChannel "child" objects to hold with reference counting.
3. AudioChannel class - this is based on the CharacterDevice class, and
represents hardware PCM audio channel. It facilitates an ioctl interface
which should be consistent across all supported hardware currently.
It has a weak reference to a parent AudioController, and when trying to
write to a channel, it redirects the data to the parent AudioController.
Each audio channel device should be added into a new directory under the
/dev filesystem called "audio".
