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.
A virtual method named device_name() was added to
Kernel::PCI to support logging the PCI::Device name
and address using dmesgln_pci. Previously, PCI::Device
did not store the device name.
All devices inheriting from PCI::Device now use dmesgln_pci where
they previously used dmesgln.
This step would ideally not have been necessary (increases amount of
refactoring and templates necessary, which in turn increases build
times), but it gives us a couple of nice properties:
- SpinlockProtected inside Singleton (a very common combination) can now
obtain any lock rank just via the template parameter. It was not
previously possible to do this with SingletonInstanceCreator magic.
- SpinlockProtected's lock rank is now mandatory; this is the majority
of cases and allows us to see where we're still missing proper ranks.
- The type already informs us what lock rank a lock has, which aids code
readability and (possibly, if gdb cooperates) lock mismatch debugging.
- The rank of a lock can no longer be dynamic, which is not something we
wanted in the first place (or made use of). Locks randomly changing
their rank sounds like a disaster waiting to happen.
- In some places, we might be able to statically check that locks are
taken in the right order (with the right lock rank checking
implementation) as rank information is fully statically known.
This refactoring even more exposes the fact that Mutex has no lock rank
capabilites, which is not fixed here.
This class is intended to replace all IOAddress usages in the Kernel
codebase altogether. The idea is to ensure IO can be done in
arch-specific manner that is determined mostly in compile-time, but to
still be able to use most of the Kernel code in non-x86 builds. Specific
devices that rely on x86-specific IO instructions are already placed in
the Arch/x86 directory and are omitted for non-x86 builds.
The reason this works so well is the fact that x86 IO space acts in a
similar fashion to the traditional memory space being available in most
CPU architectures - the x86 IO space is essentially just an array of
bytes like the physical memory address space, but requires x86 IO
instructions to load and store data. Therefore, many devices allow host
software to interact with the hardware registers in both ways, with a
noticeable trend even in the modern x86 hardware to move away from the
old x86 IO space to exclusively using memory-mapped IO.
Therefore, the IOWindow class encapsulates both methods for x86 builds.
The idea is to allow PCI devices to be used in either way in x86 builds,
so when trying to map an IOWindow on a PCI BAR, the Kernel will try to
find the proper method being declared with the PCI BAR flags.
For old PCI hardware on non-x86 builds this might turn into a problem as
we can't use port mapped IO, so the Kernel will gracefully fail with
ENOTSUP error code if that's the case, as there's really nothing we can
do within such case.
For general IO, the read{8,16,32} and write{8,16,32} methods are
available as a convenient API for other places in the Kernel. There are
simply no direct 64-bit IO API methods yet, as it's not needed right now
and is not considered to be Arch-agnostic too - the x86 IO space doesn't
support generating 64 bit cycle on IO bus and instead requires two 2
32-bit accesses. If for whatever reason it appears to be necessary to do
IO in such manner, it could probably be added with some neat tricks to
do so. It is recommended to use Memory::TypedMapping struct if direct 64
bit IO is actually needed.
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.
All users which relied on the default constructor use a None lock rank
for now. This will make it easier to in the future remove LockRank and
actually annotate the ranks by searching for None.
We now only reset the PCM out channel during initialization, and handle
the case where the channel's current index has passed the last valid
index properly.
This fixes issues with stuttering audio between multiple subsequent
`aplay` invocations, for example.
This might help with debugging on bare metal. Since the minimum version
that can be specified is revision 2.1, and we do not use any feature
from revision 2.2 or newer, this is merely future-proofing ourselves
for new features yet to be built. Additionally, removing the `VERIFY()`
ensures we will not crash on cards that only support earlier revisions.
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".
The fixes are:
1. Don't copy PCI::DeviceIdentifier during construction. This is a heavy
structure to copy so we definitely don't want to do that. Instead, use
a const reference to it like what happens in other parts in the Kernel.
2. Declare the constructor as explicit to avoid construction errors.
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.
Executing `asctl set r 96000` no longer results in weird sample rates
being set on the audio devices. SB16 checks for a sample rate between 1
and 44100 Hz, while AC97 implements double-rate support which allows
sample rates between 8kHz and 96kHZ.
This factors out some hardcoded PCMOut registers into a new private
class called AC97Channel, which wraps around a channel's registers and
provides some shared functionality.
No functional changes.
