Support Linux framebuffer and input system

Though TWIN (and by extension, Mado) was designed to operate in single-threaded
environments, the Linux framebuffer backend in Mado currently uses POSIX thread
to manage input system events. Coroutines could potentially be used as an
alternative.

Author: shengwen-tw

Makefile

@@ -104,6 +104,12 @@ libtwin.a_cflags-y += $(shell sdl2-config --cflags)
 TARGET_LIBS += $(shell sdl2-config --libs)
 endif
 
+ifeq ($(CONFIG_BACKEND_FBDEV), y)
+BACKEND = fbdev
+libtwin.a_files-y += backend/fbdev.c
+libtwin.a_files-y += backend/linux_input.c
+endif
+
 # Standalone application
 
 ifeq ($(CONFIG_DEMO_APPLICATIONS), y)

backend/fbdev.c

@@ -0,0 +1,278 @@
+/*
+ * Twin - A Tiny Window System
+ * Copyright (c) 2024 National Cheng Kung University, Taiwan
+ * All rights reserved.
+ */
+
+#include <fcntl.h>
+#include <linux/fb.h>
+#include <linux/kd.h>
+#include <linux/vt.h>
+#include <stdlib.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <twin.h>
+#include <unistd.h>
+
+#include "linux_input.h"
+#include "twin_backend.h"
+#include "twin_private.h"
+
+#define FBDEV_NAME "FRAMEBUFFER"
+#define FBDEV_DEFAULT "/dev/fb0"
+#define SCREEN(x) ((twin_context_t *) x)->screen
+#define PRIV(x) ((twin_fbdev_t *) ((twin_context_t *) x)->priv)
+
+typedef struct {
+    twin_screen_t *screen;
+
+    /* Linux input system */
+    void *input;
+
+    /* Linux virtual terminal (VT) */
+    int vt_fd;
+    int vt_num;
+    bool vt_active;
+
+    /* Linux framebuffer */
+    int fb_fd;
+    struct fb_var_screeninfo fb_var;
+    struct fb_fix_screeninfo fb_fix;
+    uint16_t cmap[3][256];
+    uint8_t *fb_base;
+    size_t fb_len;
+} twin_fbdev_t;
+
+static void _twin_fbdev_put_span(twin_coord_t left,
+                                 twin_coord_t top,
+                                 twin_coord_t right,
+                                 twin_argb32_t *pixels,
+                                 void *closure)
+{
+    twin_screen_t *screen = SCREEN(closure);
+    twin_fbdev_t *tx = PRIV(closure);
+
+    if (tx->fb_base == MAP_FAILED)
+        return;
+
+    twin_coord_t width = right - left;
+    off_t off = top * screen->width + left;
+    uint32_t *src = pixels;
+    uint32_t *dest =
+        (uint32_t *) ((uintptr_t) tx->fb_base + (off * sizeof(uint32_t)));
+    memcpy(dest, src, width * sizeof(uint32_t));
+}
+
+static void twin_fbdev_get_screen_size(twin_fbdev_t *tx,
+                                       int *width,
+                                       int *height)
+{
+    struct fb_var_screeninfo info;
+    ioctl(tx->fb_fd, FBIOGET_VSCREENINFO, &info);
+    *width = info.xres;
+    *height = info.yres;
+}
+
+static void twin_fbdev_damage(twin_screen_t *screen, twin_fbdev_t *tx)
+{
+    int width, height;
+    twin_fbdev_get_screen_size(tx, &width, &height);
+    twin_screen_damage(tx->screen, 0, 0, width, height);
+}
+
+static bool twin_fbdev_work(void *closure)
+{
+    twin_screen_t *screen = SCREEN(closure);
+
+    if (twin_screen_damaged(screen))
+        twin_screen_update(screen);
+    return true;
+}
+
+static bool twin_fbdev_apply_config(twin_fbdev_t *tx)
+{
+    /* Read changable information of the framebuffer */
+    if (ioctl(tx->fb_fd, FBIOGET_VSCREENINFO, &tx->fb_var) == -1) {
+        log_error("Failed to get framebuffer information");
+        return false;
+    }
+
+    /* Set the virtual screen size to be the same as the physical screen */
+    tx->fb_var.xres_virtual = tx->fb_var.xres;
+    tx->fb_var.yres_virtual = tx->fb_var.yres;
+    tx->fb_var.bits_per_pixel = 32;
+    if (ioctl(tx->fb_fd, FBIOPUT_VSCREENINFO, &tx->fb_var) < 0) {
+        log_error("Failed to set framebuffer mode");
+        return false;
+    }
+
+    /* Read changable information of the framebuffer again */
+    if (ioctl(tx->fb_fd, FBIOGET_VSCREENINFO, &tx->fb_var) < 0) {
+        log_error("Failed to get framebuffer information");
+        return false;
+    }
+
+    /* Check bits per pixel */
+    if (tx->fb_var.bits_per_pixel != 32) {
+        log_error("Failed to set framebuffer bpp to 32");
+        return false;
+    }
+
+    /* Read unchangable information of the framebuffer */
+    ioctl(tx->fb_fd, FBIOGET_FSCREENINFO, &tx->fb_fix);
+
+    /* Align the framebuffer memory address with the page size */
+    off_t pgsize = getpagesize();
+    off_t start = (off_t) tx->fb_fix.smem_start & (pgsize - 1);
+
+    /* Round up the framebuffer memory size to match the page size */
+    tx->fb_len = start + (size_t) tx->fb_fix.smem_len + (pgsize - 1);
+    tx->fb_len &= ~(pgsize - 1);
+
+    /* Map framebuffer device to the virtual memory */
+    tx->fb_base = mmap(NULL, tx->fb_len, PROT_READ | PROT_WRITE, MAP_SHARED,
+                       tx->fb_fd, 0);
+    if (tx->fb_base == MAP_FAILED) {
+        log_error("Failed to mmap framebuffer");
+        return false;
+    }
+
+    return true;
+}
+
+static int twin_vt_open(int vt_num)
+{
+    int fd;
+
+    char vt_dev[30] = {0};
+    snprintf(vt_dev, 30, "/dev/tty%d", vt_num);
+
+    fd = open(vt_dev, O_RDWR);
+    if (fd < 0) {
+        log_error("Failed to open %s", vt_dev);
+    }
+
+    return fd;
+}
+
+static bool twin_vt_setup(twin_fbdev_t *tx)
+{
+    /* Open VT0 to inquire information */
+    if ((tx->vt_fd = twin_vt_open(0)) < -1) {
+        return false;
+    }
+
+    /* Inquire for current VT number */
+    struct vt_stat vt;
+    if (ioctl(tx->vt_fd, VT_GETSTATE, &vt) == -1) {
+        log_error("Failed to get VT number");
+        return false;
+    }
+    tx->vt_num = vt.v_active;
+
+    /* Open the VT */
+    if ((tx->vt_fd = twin_vt_open(tx->vt_num)) < -1) {
+        return false;
+    }
+
+    /* Set VT to graphics mode to inhibit command-line text */
+    if (ioctl(tx->vt_fd, KDSETMODE, KD_GRAPHICS) < 0) {
+        log_error("Failed to set KD_GRAPHICS mode");
+        return false;
+    }
+
+    return true;
+}
+
+twin_context_t *twin_fbdev_init(int width, int height)
+{
+    char *fbdev_path = getenv(FBDEV_NAME);
+    if (!fbdev_path) {
+        log_info("Environment variable $FRAMEBUFFER not set, use %s by default",
+                 FBDEV_DEFAULT);
+        fbdev_path = FBDEV_DEFAULT;
+    }
+
+    twin_context_t *ctx = calloc(1, sizeof(twin_context_t));
+    if (!ctx)
+        return NULL;
+    ctx->priv = calloc(1, sizeof(twin_fbdev_t));
+    if (!ctx->priv)
+        return NULL;
+
+    twin_fbdev_t *tx = ctx->priv;
+
+    /* Open the framebuffer device */
+    tx->fb_fd = open(fbdev_path, O_RDWR);
+    if (tx->fb_fd == -1) {
+        log_error("Failed to open %s", fbdev_path);
+        goto bail;
+    }
+
+    /* Set up virtual terminal environment */
+    if (!twin_vt_setup(tx)) {
+        goto bail_fb_fd;
+    }
+
+    /* Apply configurations to the framebuffer device */
+    if (!twin_fbdev_apply_config(tx)) {
+        log_error("Failed to apply configurations to the framebuffer device");
+        goto bail_vt_fd;
+    }
+
+    /* Create TWIN screen */
+    ctx->screen =
+        twin_screen_create(width, height, NULL, _twin_fbdev_put_span, ctx);
+
+    /* Create Linux input system object */
+    tx->input = twin_linux_input_create(ctx->screen);
+    if (!tx->input) {
+        log_error("Failed to create Linux input system object");
+        goto bail_vt_fd;
+    }
+
+    /* Setup file handler and work functions */
+    twin_set_work(twin_fbdev_work, TWIN_WORK_REDISPLAY, ctx);
+
+    return ctx;
+
+bail_vt_fd:
+    close(tx->vt_fd);
+bail_fb_fd:
+    close(tx->fb_fd);
+bail:
+    free(ctx->priv);
+    free(ctx);
+    return NULL;
+}
+
+static void twin_fbdev_configure(twin_context_t *ctx)
+{
+    int width, height;
+    twin_fbdev_t *tx = ctx->priv;
+    twin_fbdev_get_screen_size(tx, &width, &height);
+    twin_screen_resize(ctx->screen, width, height);
+}
+
+static void twin_fbdev_exit(twin_context_t *ctx)
+{
+    if (!ctx)
+        return;
+
+    twin_fbdev_t *tx = PRIV(ctx);
+    ioctl(tx->vt_fd, KDSETMODE, KD_TEXT);
+    munmap(tx->fb_base, tx->fb_len);
+    twin_linux_input_destroy(tx->input);
+    close(tx->vt_fd);
+    close(tx->fb_fd);
+    free(ctx->priv);
+    free(ctx);
+}
+
+/* Register the Linux framebuffer backend */
+
+const twin_backend_t g_twin_backend = {
+    .init = twin_fbdev_init,
+    .configure = twin_fbdev_configure,
+    .exit = twin_fbdev_exit,
+};