#pragma once

// Framebuffer device ABI -- /dev/fb0.
//
// These are Linux's fbdev request numbers and structure layouts, not ours.
// SchOS invented this device, so nothing forced the choice; matching Linux
// was still the right one. A framebuffer is the first thing a graphics
// program looks for, and every such program already knows how to ask
// FBIOGET_VSCREENINFO. Inventing a private struct would have meant patching
// each one we ever port, and -- worse -- a Linux-ABI binary calling
// FBIOGET_VSCREENINFO would have gotten a *differently shaped* answer to a
// request it thought it understood, which is the failure mode that made
// `>>` truncate back when include/fcntl.h held xv6's open flags instead of
// Linux's. Same lesson, applied before it bites rather than after.
//
// Plain C types throughout (no types.h) so userspace can include this
// directly. Both sides are LP64.

#define FBIOGET_VSCREENINFO 0x4600
#define FBIOPUT_VSCREENINFO 0x4601
#define FBIOGET_FSCREENINFO 0x4602
#define FBIOBLANK           0x4611

// fb_fix_screeninfo.type
#define FB_TYPE_PACKED_PIXELS 0

// fb_fix_screeninfo.visual
#define FB_VISUAL_TRUECOLOR 2

// fb_var_screeninfo.activate
#define FB_ACTIVATE_NOW 0

// One colour channel's position within a pixel. `offset` is the bit position
// of the channel's least significant bit; `length` is how many bits it gets.
// A length of 0 means the channel does not exist -- which is how an opaque
// framebuffer reports `transp`.
struct fb_bitfield {
    unsigned int offset;
    unsigned int length;
    unsigned int msb_right;   // != 0 means bit 0 is the MSB; never here
};

struct fb_var_screeninfo {
    unsigned int xres;             // visible resolution
    unsigned int yres;
    unsigned int xres_virtual;     // virtual resolution; == visible, no panning
    unsigned int yres_virtual;
    unsigned int xoffset;          // offset of visible area within virtual
    unsigned int yoffset;
    unsigned int bits_per_pixel;
    unsigned int grayscale;        // 0 == colour
    struct fb_bitfield red;
    struct fb_bitfield green;
    struct fb_bitfield blue;
    struct fb_bitfield transp;
    unsigned int nonstd;           // 0 == standard pixel format
    unsigned int activate;
    unsigned int height;           // physical size in mm; 0 == unknown, and
    unsigned int width;            // VBE does not tell us, so it stays 0
    unsigned int accel_flags;
    // Timings. The mode is whatever the bootloader's VBE call established and
    // we cannot change it, so these are all reported as zero rather than
    // invented.
    unsigned int pixclock;
    unsigned int left_margin;
    unsigned int right_margin;
    unsigned int upper_margin;
    unsigned int lower_margin;
    unsigned int hsync_len;
    unsigned int vsync_len;
    unsigned int sync;
    unsigned int vmode;
    unsigned int rotate;
    unsigned int colorspace;
    unsigned int reserved[4];
};

struct fb_fix_screeninfo {
    char id[16];                   // "schosfb"
    unsigned long smem_start;      // physical address of the framebuffer
    unsigned int smem_len;         // its length in bytes
    unsigned int type;
    unsigned int type_aux;
    unsigned int visual;
    unsigned short xpanstep;       // 0 == panning unsupported
    unsigned short ypanstep;
    unsigned short ywrapstep;
    unsigned int line_length;      // bytes per scanline (the VBE stride, which
                                   // is NOT always xres * bytes_per_pixel)
    unsigned long mmio_start;      // no separate register aperture
    unsigned int mmio_len;
    unsigned int accel;            // no acceleration
    unsigned short capabilities;
    unsigned short reserved[2];
};