This value will be used later on by WindowServer to reject resolutions
that will request a mapping that will overflow the hardware framebuffer
max length.
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.
The new VGAIOArbiter class is now responsible to conduct x86-specific
instructions to control VGA hardware from the old ISA ports. This allows
us to ensure the GraphicsManagement code doesn't use x86-specific code,
thus allowing it to be compiled within non-x86 kernel builds.
The BootFramebufferConsole highly depends on using the m_lock spinlock,
therefore setting and changing the cursor state should be done under
that spinlock too to avoid crashing.
Only the Console code in the Graphics directory should be able to call
on these methods. The set_cursor method stays public as VirtualConsole
uses that method to change the cursor position.
This device is supposed to be used in microvm and ISA-PC machine types,
and we assume that if we are able to probe for the QEMU BGA version of
0xB0C5, then we have an existing ISA Bochs VGA adapter to utilize.
To ensure we don't instantiate the driver for non isa-vga devices, we
try to ensure that PCI is disabled because hardware IO test probe failed
so we can be sure that we use this special handling code only in the
QEMU microvm and ISA-PC machine types. Unfortunately, this means that if
for some reason the isa-vga device is attached for the i440FX or Q35
machine types, we simply are not able to drive the device in such setups
at all.
To determine the amount of VRAM being available, we read VBE register at
offset 0xA. That register holds the amount of VRAM divided by 64K, so we
need to multiply the value in our code to use the actual VRAM size value
again.
The isa-vga device requires us to hardcode the framebuffer physical
address to 0xE0000000, and that address is not expected to change in the
future as many other projects rely on the isa-vga framebuffer to be
present at that physical memory address.
We use a ScopeGuard to ensure we always set a console of some sort if we
exit early from the initialization sequence in the GraphicsManagement
code. We do so to ensure we can boot into text mode console in an ISA-PC
machine type, because earlier we failed with an assertion due to not
setting any console for VirtualConsole to use.
The AHCI code doesn't rely on x86 IO at all as it only uses memory
mapped IO so we can simply remove the header.
We also simply don't use x86 IO in the Intel graphics driver, so we can
simply remove the include of the x86 IO header there too.
Everything else was a bunch of stale includes to the x86 IO header and
are actually not necessary, so let's remove them to make it easier to
compile non-x86 Kernel builds.
Many code patterns and hardware procedures rely on reliable delay in the
microseconds granularity, and since they are using such delays which are
valid cases, but should not rely on x86 specific code, we allow to
determine in compile time the proper platform-specific code to use to
invoke such delays.
Before this change, we had File::mmap() which did all the work of
setting up a VMObject, and then creating a Region in the current
process's address space.
This patch simplifies the interface by removing the region part.
Files now only have to return a suitable VMObject from
vmobject_for_mmap(), and then sys$mmap() itself will take care of
actually mapping it into the address space.
This fixes an issue where we'd try to block on I/O (for inode metadata
lookup) while holding the address space spinlock. It also reduces time
spent holding the address space lock.
This forces anyone who wants to look into and/or manipulate an address
space to lock it. And this replaces the previous, more flimsy, manual
spinlock use.
Note that pointers *into* the address space are not safe to use after
you unlock the space. We've got many issues like this, and we'll have
to track those down as wlel.
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.
Instead of having two separate implementations of AK::RefCounted, one
for userspace and one for kernelspace, there is now RefCounted and
AtomicRefCounted.
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 should actually start counting from the parent directory and not from
the symbolic link as it will represent a wrong count of hops from the
actual mountpoint.
The symlinks in /sys/dev/block and /sys/dev/char worked only by luck,
because I have set it to the wrong parent directory which is the
/sys/dev directory, so with the symlink it was 3 hops to /sys, together
with the root directory, therefore, everything seemed to work.
Now that the device symlinks in /sys/dev/block and /sys/dev/char are set
to the right parent directory and we start measure hops from root
directory with the parent directory of a symlink, everything seem to
work correctly now.
Now that the infrastructure of the Graphics subsystem is quite stable,
it is time to try to fix a long-standing problem, which is the lack of
locking on display connector devices. Reading and writing from multiple
processes to a framebuffer controlled by the display connector is not a
huge problem - it could be solved with POSIX locking.
The real problem is some program that will try to do ioctl operations on
a display connector without the WindowServer being aware of that which
can lead to very bad situations, for example - assuming a framebuffer is
encoded at a known resolution and certain display timings, but another
process changed the ModeSetting of the display connector, leading to
inconsistency on the properties of the current ModeSetting.
To solve this, there's a new "master" ioctl to take "ownership" and
another one to release that ownership of a display connector device. To
ensure we will not hold a Process object forever just because it has an
ownership over a display connector, we hold it with a weak reference,
and if the process is gone, someone else can take an ownership.
We are able to read the EDID from SysFS, therefore there's no need to
provide this ioctl on a DisplayConnector anymore.
Also, now we can simply require the video pledge to be set before doing
any ioctl on a DisplayConnector.
It is starting to get a little messy with how each device can try to add
or remove itself to either /sys/dev/block or /sys/dev/char directories.
To better do this, we introduce 4 virtual methods to take care of that,
so until we ensure all nodes in /sys/dev/block and /sys/dev/char are
actual symlinks, we allow the Device base class to call virtual methods
upon insertion or before being destroying, so it add itself elegantly to
either of these directories or remove itself when needed.
For special cases where we need to create symlinks, we have two virtual
methods to be called otherwise to do almost the same thing mentioned
before, but to use symlinks instead.
Under normal conditions (when mounting SysFS in /sys), there will be a
new directory in the /sys/devices directory called "graphics".
For now, under that directory there will be only a sub-directory called
"connectors" which will contain all DisplayConnectors' details, each in
its own sub-directory too, distinguished in naming with its minor
number.
Therefore, /sys/devices/graphics/connectors/MINOR_NUMBER/ will contain:
- General device attributes such as mutable_mode_setting_capable,
double_buffering_capable, flush_support, partial_flush_support and
refresh_rate_support. These values are exposed in the ioctl interface
of the DisplayConnector class too, but these can be useful later on
for command line utilities that want/need to expose these basic
settings.
- The EDID blob, simply named "edid". This will help userspace to fetch
the edid without the need of using the ioctl interface later on.
There's no point in keeping this method as we don't really care if a
graphics adapter is VGA compatible or not because we don't use this
method anymore.
We should not allocate a kernel region inside the constructor of the
VGATextModeConsole class. We do use MUST() because allocation cannot
fail at this point, but that happens in the static factory method
instead.
The original intention was to support other types of consoles based on
standard VGA modes, but it never came to an implementation, nor we need
such feature at all.
Therefore, this class is not needed and can be removed.
Each of these strings would previously rely on StringView's char const*
constructor overload, which would call __builtin_strlen on the string.
Since we now have operator ""sv, we can replace these with much simpler
versions. This opens the door to being able to remove
StringView(char const*).
No functional changes.
We never supported VGA framebuffers and that folder was a big misleading
part of the graphics subsystem.
We do support bare-bones VGA text console (80x25), but that only happens
to be supported because we can't be 100% sure we can always initialize
framebuffer so in the worst scenario we default to plain old VGA console
so the user can still use its own machine.
Therefore, the only remaining parts of VGA is in the GraphicsManagement
code to help driving the VGA text console if needed.
In the same fashion like in the Linux kernel, we support pre-initialized
framebuffers that were set up by either the BIOS or the bootloader.
These framebuffers can be backed by any kind of video hardware, and are
not tied to VGA hardware at all. Therefore, this code should be in a
separate sub-folder in the Graphics subsystem to indicate this.
Move methods that are overriding the virtual methods in the File class,
to a private access scope in the DisplayConnector class because nobody
tries to access them in any derived class of this class.
- Remove some magic numbers
- Remove some duplicate branches
- Reduce the amount of casting between u8* and u32*
- Some renaming of confusing variables
The WindowServer doesn't use this interface anymore and therefore it's
not used by any userspace application, so let's remove this stale method
to ensure we don't have to bother with it anymore.
The mmap interface was removed when we introduced the DisplayConnector
class, as it was quite unsafe to use and didn't handle switching between
graphical and text modes safely. By using the SharedFramebufferVMObject,
we are able to elegantly coordinate the switch by remapping the attached
mmap'ed-Memory::Region(s) with different mappings, therefore, keeping
WindowServer to think that the mappings it has are still valid, while
they are going to a different physical range until we are back to the
graphical mode (after a switch from text mode).
Most drivers take advantage of the fact that we know where is the actual
framebuffer in physical memory space, the SharedFramebufferVMObject is
created with that information. However, the VirtIO driver is different
in that aspect, because it relies on DMA transactions to show graphics
on the framebuffer, so the SharedFramebufferVMObject is created with
that mindset to support the arbitrary framebuffer location in physical
memory space.
Keeping the exact details of a dirty rectangle doesn't make any sense
when we just flush the entire screen, so just keep a simple boolean
value to know if the screen needs to be flushed or not.
This fixes a weird bug that when sometimes a user tried to switch to
console mode, the screen was frozen on graphics mode. After a hour of
debugging this, it became apparent that the problem was that we left the
y offset of the bochs graphics device in an invalid state, so it was not
zero because the WindowServer changed it, and the framebuffer console
code is not aware of horizontal and vertical offsets of the framebuffer
screen, leading to the problem that the framebuffer console updates the
first framebuffer (y offset = 0), but hardware was indicated to show the
second framebuffer (y offset = first framebuffer height).
Therefore, when doing a switch between these modes, always set the y
offset to be zero.
This in turn makes the built-in kernel console much more nicer to look
into, so let's remove the support for 8x8 bitmap and instead add 8x16
font bitmap.
