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.
The old methods are already can be considered deprecated, and now after
we removed framebuffer devices entirely, we can safely remove these
methods too, which simplfies the GenericGraphicsAdapter class a lot.
Instead of letting the user to determine whether framebuffer devices
will be created (which is useless because they are gone by now), let's
simplify the flow by allowing the user to choose between full, limited
or disabled functionality. The determination happens only once, so, if
the user decided to disable graphics support, the initialize method
exits immediately. If limited functionality is chosen, then a generic
DisplayConnector is initialized with the preset framebuffer resolution,
if present, and then the initialize method exits. As a default, the code
proceeds to initialize all drivers as usual.
We shouldn't expose the VirtIO GPU3DDevice constructor as public method,
so instead, let's use the usual pattern of a static construction method
that uses the constructor within the method.
The DisplayConnector class is meant to replace the FramebufferDevice
class. The advantage of this class over the FramebufferDevice class is:
1. It removes the mmap interface entirely. This interface is unsafe, as
multiple processes could try to use it, and when switching to and from
text console mode, there's no "good" way to revoke a memory mapping from
this interface, let alone when there are multiple processes that call
this interface. Therefore, in the DisplayConnector class there's no
implementation for this method at all.
2. The class uses a new real-world structure called ModeSetting, which
takes into account the fact that real hardware requires more than width,
height and pitch settings to mode-set the display resolution.
3. The class assumes all instances should supply some sort of EDID,
so it facilitates such mechanism to do so. Even if a given driver does
not know what is the actual EDID, it will ask to create default-generic
EDID blob.
3. This class shifts the responsibilies of switching between console
mode and graphical mode from a GraphicsAdapter to the DisplayConnector
class, so when doing the switch, the GraphicsManagement code actually
asks each DisplayConnector object to do the switch and doesn't rely on
the GraphicsAdapter objects at all.
In most cases it's safe to abort the requested operation and go forward,
however, in some places it's not clear yet how to handle these failures,
therefore, we use the MUST() wrapper to force a kernel panic for now.
This helps solving an issue when we boot with text mode screen so the
Kernel initializes an early text mode console, but even after disabling
it, that console can still access VGA ports. This wouldn't be a problem
for emulated hardware but bare metal hardware might have a "conflict",
especially if the native driver explicitly request to disable the VGA
emulation.
