Vystem 0.2

docs/shelter/kernel/efifb.md

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+# EFI framebuffer
+
+## Introduction
+
+This subsystem aims to provide a simple way to indicate the boot process state using a progress bar displayed on the EFI GOP framebuffer. For the moment, only framebuffers using 32 bits pixel format are supported. It's defined in `shelter/lib/include/kernel/efifb.h` and implemented in `shelter/lib/src/kernel/efifb.c`.
+
+## Overview
+
+To avoid any complex colors encoding, pixel values for the colors white and gray must be provided through the framebuffer configuration.
+
+The framebuffer parameters are loaded using the `sh_efifb_init_fb(sh_conf_FB_CONFIG *fb_conf,sh_page_PAGE_TABLE_POOL *ptp)` function. This function will:
+1) Load framebuffers dimensions
+2) Identity map the whole framebuffers
+3) Erase the previous texts on the framebuffer, based on the information provided in the framebuffer configuration
+
+The progress bar is initialized using `sh_efifb_init_bar()`. It will draw an empty progress bar.
+
+Finally, to update the progress bar, the `sh_efifb_set_bar(sh_uint8 percent)` function is used.