a1c965da1e
Sixty-five headers sat side by side in include/, so `#include "irq.h"` said nothing about where irq.h was or what it belonged to, and errno.h, stat.h and fcntl.h at the top shadowed the system's for any host tool built with -I./include. They are in folders now -- arch/ core/ fs/ dev/ gfx/ net/ uapi/ (and ldls/ for the Linux driver layer) -- and every include names the folder, as Linux's do: "core/proc.h". Done mechanically and checked the hard way: the kernel built from this tree disassembles identically to the one built from the tree before it. The full image boots, and userland is the same set of programs. Paths in docs and comments follow; docs/guides/layout.md has a table of what is where, and tools/fix-includes.py rewrites old-style includes from the folders in the tree, for code written before this. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4
71 lines
3 KiB
C
71 lines
3 KiB
C
#pragma once
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// The display class: what a consumer talks to instead of a driver.
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//
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// A compositor should ask for "the display" and get whatever is bound --
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// today the VBE framebuffer, later virtio-gpu. Without this, every consumer
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// names a driver, and adding the second display driver means editing all of
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// them. That is not hypothetical here: the framebuffer's physical address was
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// once hardcoded in three separate places.
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//
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// Found with device_find_class(DEVCLASS_DISPLAY); see include/dev/device.h.
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struct device;
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struct display_mode {
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int width, height;
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int bpp;
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uint32 stride; // bytes per row of the *visible* framebuffer
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};
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struct display_ops {
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void (*mode)(struct device *, struct display_mode *);
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// The buffer to draw into, and its stride. Returns 0 if double buffering is
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// unavailable, in which case the caller should draw directly and accept
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// tearing rather than not drawing at all.
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//
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// Allocated on first call, never at boot: it is around two megabytes at
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// 800x600, and a machine whose compositor never starts should not pay that.
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void *(*acquire)(struct device *, uint32 *stride_out);
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// Copy a rectangle of the back buffer to the display. Coordinates are in
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// pixels; the whole screen is (0, 0, width, height).
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void (*present)(struct device *, int x, int y, int w, int h);
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// Block until the display is between frames. Optional -- a driver that
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// cannot tell leaves this null, and present() then simply tears less than
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// drawing directly would.
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void (*wait_vblank)(struct device *);
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// The physical address this device is scanning out from.
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//
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// Which answers a question acquire() cannot: **is this screen the console's
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// screen, or another one?** The buffer acquire() returns is not the answer,
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// because a driver is free to hand back a back buffer it will later copy
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// onto the console's own framebuffer -- vga_fb does exactly that, and a
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// console mirror that believed the pointer copied the console onto itself
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// through two megabytes of intermediate.
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//
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// A fact about the hardware rather than a policy, so a driver cannot get it
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// subtly wrong: compare it with gfx_fb_phys(). Optional; a driver that
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// leaves it null is assumed to be the console's, which is the safe way round
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// -- it costs a second screen nothing is drawn on, not a wrong picture.
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uint64 (*scanout_phys)(struct device *);
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};
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// The bound display, or 0. Convenience over device_find_class().
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struct device *display_get(void);
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// Wrappers that do nothing gracefully when there is no display or the driver
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// left an op null, so callers are not each written around a maybe-null vtable.
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int display_mode(struct display_mode *out);
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void *display_acquire(uint32 *stride_out);
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void display_present(int x, int y, int w, int h);
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void display_wait_vblank(void);
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// Drive the whole path once and draw a test pattern. `echo d > /proc/sysrq`.
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void display_selftest(void);
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// Draw a text specimen through the display class. `echo t > /proc/sysrq`.
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void text_selftest(void);
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