From 0d2dfeca9318e954cbbd1f719b65f8a5c5eacd38 Mon Sep 17 00:00:00 2001
From: Hunter Kvalevog <hunter@kvog.sh>
Date: Sun, 15 Feb 2026 09:59:38 -0600
Subject: rl: New build system, arm64 support

---
 rushmore-linux/rlws/rlws.c | 140 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 140 insertions(+)
 create mode 100644 rushmore-linux/rlws/rlws.c

(limited to 'rushmore-linux/rlws')

diff --git a/rushmore-linux/rlws/rlws.c b/rushmore-linux/rlws/rlws.c
new file mode 100644
index 0000000..87882df
--- /dev/null
+++ b/rushmore-linux/rlws/rlws.c
@@ -0,0 +1,140 @@
+#include <errno.h>
+#include <fcntl.h>
+#include <linux/fb.h>
+#include <linux/kd.h>
+#include <stdarg.h>
+#include <string.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <sys/mman.h>
+#include <sys/ioctl.h>
+#include <sys/uio.h>
+#include <time.h>
+#include <unistd.h>
+
+static const char* tmp_fmt(const char* fmt, ...)
+{
+    static char msg[1024] = { 0 };
+    va_list va; va_start(va, fmt);
+    vsnprintf(msg, sizeof(msg), fmt, va);
+    va_end(va);
+    return msg;
+}
+
+static void spew(const char* message)
+{
+    // Kernel log is available after init
+    int kmfd = open("/dev/kmsg", O_WRONLY | O_CLOEXEC);
+
+    struct iovec msgvec[] = {
+#define STRVEC(str) { .iov_base = (void*)(str), .iov_len = __builtin_strlen(str) }
+        STRVEC("rlwsd: "),
+        STRVEC(message),
+        STRVEC("\n")
+#undef STRVEC
+    };
+    writev(kmfd, msgvec, sizeof(msgvec) / sizeof(*msgvec));
+
+    close(kmfd);
+}
+
+static void panic(const char* message)
+{
+    spew(message);
+    _exit(1); // Triggers a kernel panic since we're PID 1
+}
+
+static inline uint32_t pack_rgb(const struct fb_var_screeninfo* v, uint8_t r, uint8_t g, uint8_t b)
+{
+    uint32_t rv = (v->red.length   ? ((uint32_t)r * ((1u << v->red.length)   - 1) + 127) / 255 : 0);
+    uint32_t gv = (v->green.length ? ((uint32_t)g * ((1u << v->green.length) - 1) + 127) / 255 : 0);
+    uint32_t bv = (v->blue.length  ? ((uint32_t)b * ((1u << v->blue.length)  - 1) + 127) / 255 : 0);
+    return (rv << v->red.offset) | (gv << v->green.offset) | (bv << v->blue.offset);
+}
+
+static inline void write_pixel(uint8_t* p, uint32_t bpp, uint32_t pix)
+{
+    uint32_t bytes = bpp / 8;
+    for (uint32_t i = 0; i < bytes; i++)
+        p[i] = (uint8_t)(pix >> (8u * i)); // little-endian write
+}
+
+int main(void)
+{
+    int fd = open("/dev/fb0", O_RDWR | O_CLOEXEC);
+    if (fd < 0) {
+        panic(tmp_fmt("Failed to open /dev/fb0: %s", strerror(errno)));
+    }
+
+    struct fb_fix_screeninfo finfo;
+    struct fb_var_screeninfo vinfo;
+    if (ioctl(fd, FBIOGET_FSCREENINFO, &finfo) != 0) {
+        panic(tmp_fmt("FBIOGET_FSCREENINFO: %s", strerror(errno)));
+    }
+    if (ioctl(fd, FBIOGET_VSCREENINFO, &vinfo) != 0) {
+        panic(tmp_fmt("FBIOGET_VSCREENINFO: %s", strerror(errno)));
+    }
+
+    spew(tmp_fmt("fb0: %ux%u bpp=%u line_length=%u visual=%u",
+        vinfo.xres, vinfo.yres, vinfo.bits_per_pixel,
+        finfo.line_length, finfo.visual));
+    spew(tmp_fmt("fb0: R %u/%u G %u/%u B %u/%u",
+        vinfo.red.offset, vinfo.red.length,
+        vinfo.green.offset, vinfo.green.length,
+        vinfo.blue.offset, vinfo.blue.length));
+
+    if (!(vinfo.bits_per_pixel == 24 || vinfo.bits_per_pixel == 32)) {
+        panic("Unsupported BPP");
+    }
+
+    // Disable TTY
+    int tty = open("/dev/tty0", O_RDWR);
+    if (tty < 0) {
+        tty = open("/dev/console", O_RDWR);
+        if (tty < 0) {
+            panic(tmp_fmt("Couldn't open tty: %s", strerror(errno)));
+        }
+    }
+    if (ioctl(tty, KDSETMODE, KD_GRAPHICS) != 0) {
+        panic(tmp_fmt("Failed to set tty mode to KD_GRAPHICS: %s", strerror(errno)));
+    }
+    close(tty);
+
+    size_t fb_size = (size_t)finfo.line_length * vinfo.yres;
+    uint8_t* fb = (uint8_t*)mmap(NULL, fb_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+    if (fb == MAP_FAILED) {
+        panic(tmp_fmt("mmap failed: %s", strerror(errno)));
+    }
+
+#if 1
+    for (uint32_t y = 0; y < vinfo.yres; ++y) {
+        uint8_t* row = fb + (size_t)y * finfo.line_length;
+        memset(row, 0x00, finfo.line_length);
+    }
+#endif
+
+    uint8_t lum = 0;
+    uint32_t y = 0;
+    float then = 0.0f;
+
+    for (;;)
+    {
+        struct timespec ts;
+        clock_gettime(CLOCK_MONOTONIC, &ts);
+        float now = ts.tv_sec + (ts.tv_nsec / 1e9f);
+        if ((now - then) >= (1.0f / 60.0f)) {
+            then = now;
+
+            uint32_t pix = pack_rgb(&vinfo, lum, lum, lum);
+            uint8_t* row = fb + (size_t)y * finfo.line_length;
+            for (size_t x = 0; x < vinfo.xres; ++x) {
+                size_t bpp = vinfo.bits_per_pixel;
+                size_t bypp = bpp / 8;
+                write_pixel(&row[(size_t)x * bypp], bpp, pix);
+            }
+
+            lum = (lum + 7) % 255;
+            y = (y + 1) % (vinfo.yres - 1);
+        }
+    }
+}
-- 
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