Handout
This commit is contained in:
Niklas Gollenstede
189
kernel/device/graphics.cc
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189
kernel/device/graphics.cc
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#include "./graphics.h"
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#include "../boot/multiboot/data.h"
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#include "./debug/output.h"
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#include "./utils/string.h"
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/// Replace size with `Graphics::SCREEN_BUF_SIZE`
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/// We don't do this here, as this drastically increases the size of the kernel
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/// image.
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char frontbuffer[1] __attribute__((aligned(8)));
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char backbuffer[1] __attribute__((aligned(8)));
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/*! \brief Mode Information of the *Vesa BIOS Extension*
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*
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* \see Vesa BIOS Extension [ModeInfoBlock struc](vbe3.pdf#page=38)
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*/
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struct VbeModeInfo {
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enum ModeAttributes : uint16_t {
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SUPPORTED = 1 << 0, ///< Mode supported by hardware configuration
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TTY = 1 << 2, ///< TTY Output functions supported by BIOS
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COLOR = 1 << 3, ///< Color mode (otherwise monochrome)
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GRAPHICS = 1 << 4, ///< Graphic mode (otherwise text)
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VGA = 1 << 5, ///< VGA compatible
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VGA_PAGED =
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1 << 6, ///< VGA compatible windowed memory mode is available
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LFB = 1 << 7, ///< Linear frame buffer mode is available
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};
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uint16_t mode_attributes;
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// Window functions (used by all VBE revisions, but ignored here)
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struct __attribute__((packed)) {
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uint8_t attrib_a;
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uint8_t attrib_b;
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uint16_t granularity;
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uint16_t size;
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uint16_t segment_a;
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uint16_t segment_b;
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uint32_t func_ptr;
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} win;
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uint16_t pitch; ///< Bytes per scan line
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uint16_t
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width; ///< Horizontal resolution in pixels (GRAPHICS) or characters
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uint16_t
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height; ///< Vertical resolution in pixels (GRAPHICS) or characters
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uint8_t char_width; ///< Character cell width in pixels (deprecated)
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uint8_t char_height; ///< Character cell height in pixels (deprecated)
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uint8_t planes; ///< Number of memory planes
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uint8_t bpp; ///< Bits per pixel
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uint8_t banks; ///< Number of banks
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enum MemoryModel : uint8_t {
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TEXT_MODE = 0, ///< Text mode
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CGA = 1, ///< CGA graphics
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HERCULES = 2, ///< Hercules graphics
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PLANAR = 3, ///< Planar
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PACKED = 4, ///< Packed pixel
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NON_CHAIN_4 = 5, ///< Non-chain 4, 256 color
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DIRECT_COLOR = 6, ///< Direct Color
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YUV = 7 ///< YUV
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} memory_model; ///< Memory model type
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uint8_t bank_size; ///< Bank size in KB
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uint8_t image_pages; ///< Number of images
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uint8_t reserved; ///< Reserved for page function
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// Direct Color fields (required for DIRECT_COLOR and YUV memory models)
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uint8_t bits_red; ///< Size of direct color red mask in bits
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uint8_t offset_red; ///< Bit position of lsb of red mask
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uint8_t bits_green; ///< Size of direct color green mask in bits
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uint8_t offset_green; ///< Bit position of lsb of green mask
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uint8_t bits_blue; ///< Size of direct color blue mask in bits
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uint8_t offset_blue; ///< Bit position of lsb of blue mask
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uint8_t bits_rsv; ///< Size of direct color reserved mask in bits
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uint8_t offset_rsv; ///< Bit position of lsb of reserved mask
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enum DirectColorAttributes : uint8_t {
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DYNAMIC_COLOR_RAMP =
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1 << 0, ///< Programmable (otherwise fixed) color ramp
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USABLE_BITS =
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1 << 1 ///< Bits in reserved mask are usable (otherwise reserved)
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};
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uint8_t directcolor_attributes; ///< direct color mode attributes
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// Mandatory information for VBE 2.0 and above
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uint32_t address; ///< physical address for flat memory frame buffer
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uint32_t offscreen_memory_offset; ///< reserved
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uint16_t offscreen_memory_size; ///< reserved
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} __attribute__((packed));
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Graphics::Graphics()
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: buffer_size(SCREEN_BUF_SIZE),
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buffer{frontbuffer, backbuffer},
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scanout_buffer(0),
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refresh(false) {}
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bool Graphics::init(bool force) {
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assert(sizeof(frontbuffer) >= buffer_size &&
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sizeof(backbuffer) >= buffer_size &&
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"Buffers are too small, adjust them!!!");
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// Most boot loaders support the Vesa BIOS Extension (VBE) information quite
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// well
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Multiboot::VBE *vbe = Multiboot::getVesaBiosExtensionInfo();
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if (vbe != nullptr) {
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// However, you have to manually parse the required data out of all the
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// outdated crap
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struct VbeModeInfo *vbe_info = reinterpret_cast<struct VbeModeInfo *>(
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static_cast<uintptr_t>(vbe->mode_info));
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// Is there linear frame buffer (or just ignore the check with `force`
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// due to a misleading information)?
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if (force || (vbe_info->mode_attributes &
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VbeModeInfo::ModeAttributes::LFB) != 0) {
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// Is there a suitable precompiled graphic mode
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printer = AbstractGraphicsPrinter::getMode(
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vbe_info->bpp, vbe_info->offset_red, vbe_info->offset_green,
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vbe_info->offset_blue, vbe_info->bits_red, vbe_info->bits_green,
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vbe_info->bits_blue);
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if (printer != nullptr) {
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address = reinterpret_cast<void *>(
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static_cast<uintptr_t>(vbe_info->address));
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size = vbe_info->height * vbe_info->pitch;
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if (size > buffer_size) {
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DBG_VERBOSE << "The current graphic buffer (" << buffer_size
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<< " bytes) is too small (at least " << size
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<< " bytes required)!" << endl;
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return false;
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} else {
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printer->init(vbe_info->width, vbe_info->height,
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vbe_info->pitch);
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printer->buffer(buffer[1 - scanout_buffer]);
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return true;
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}
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}
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} else {
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DBG_VERBOSE << "Unsupported graphic mode" << endl;
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}
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}
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// Actually, \ref Multiboot::Framebuffer has everything we need in a real
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// smart structure, however boot loader like PXE don't support them (yet --
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// quite new, added in the last Multiboot revision).
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Multiboot::Framebuffer *fb = Multiboot::getFramebufferInfo();
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if (fb != nullptr) {
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if (force || fb->type == Multiboot::Framebuffer::RGB) {
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printer = AbstractGraphicsPrinter::getMode(
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fb->bpp, fb->offset_red, fb->offset_green, fb->offset_blue,
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fb->bits_red, fb->bits_green, fb->bits_blue);
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if (printer != nullptr) {
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address = reinterpret_cast<void *>(
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static_cast<uintptr_t>(fb->address));
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size = fb->height * fb->pitch;
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if (size > buffer_size) {
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DBG_VERBOSE << "The current graphic buffer (" << buffer_size
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<< " bytes) is too small (at least " << size
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<< " bytes required)!" << endl;
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return false;
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} else {
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printer->init(fb->width, fb->height, fb->pitch);
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printer->buffer(buffer[1 - scanout_buffer]);
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return true;
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}
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}
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} else {
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DBG_VERBOSE << "Unsupported graphic mode" << endl;
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}
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}
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// Unable to initialize mode
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return false;
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}
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bool Graphics::switchBuffers() {
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if (!refresh) {
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printer->buffer(buffer[scanout_buffer]);
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scanout_buffer = 1 - scanout_buffer;
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refresh = true;
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return true;
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} else {
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return false;
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}
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}
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void Graphics::scanoutFrontbuffer() {
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if (refresh) {
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memcpy(address, buffer[scanout_buffer], size);
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refresh = false;
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}
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}
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