The driver would crash if it was unable to find an output route, and
subsequently the destruction of controller did not invoke
`GenericInterruptHandler::will_be_destroyed()` because on the level of
`AudioController`, that method is unavailable.
By decoupling the interrupt handling from the controller, we get a new
refcounted class that correctly cleans up after itself :^)
We used to not care about stopping an audio output stream for Intel HDA
since AudioServer would continuously send new buffers to play. Since
707f5ac150ef858760eb9faa52b9ba80c50c4262 however, that has changed.
Intel HDA now uses interrupts to detect when each buffer was completed
by the device, and uses a simple heuristic to detect whether a buffer
underrun has occurred so it can stop the output stream.
This was tested on Qemu's Intel HDA (Linux x86_64) and a bare metal MSI
Starship/Matisse HD Audio Controller.
"Wherever applicable" = most places, actually :^), especially for
networking and filesystem timestamps.
This includes changes to unzip, which uses DOSPackedTime, since that is
changed for the FAT file systems.
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.
Instead of enumerating all available controllers and then ask each to
find its audio channels, we change the initialization sequence to match
what happens in the Networking subsystem and Graphics subsystem - we
essentially probe for a matching driver on a PCI device, create a device
instance, and immediately initialize it.
This in fact allows us to immediately find any hardware initialization
issues and report it, and then dropping the created instance, as usually
being done in other initialization paths in the Kernel.
This also opens the opportunity to propagate errors when failed to
initialize an AudioChannel instance, and it will be addressed in a
future commit.
This is an implementation that tries to follow the spec as closely as
possible, and works with Qemu's Intel HDA and some bare metal HDA
controllers out there. Compiling with `INTEL_HDA_DEBUG=on` will provide
a lot of detailed information that could help us getting this to work
on more bare metal controllers as well :^)
Output format is limited to `i16` samples for now.
