should be working, should be

git-svn-id: https://svn.vegaa.systems/svn/vega-Vega/trunk@7 a8a8aea2-181d-ee11-89e8-15fd0e089fc4

5 files changed, 659 insertions, 0 deletions

diff --git a/sys/kern/init_main.c b/sys/kern/init_main.c
new file mode 100644
index 0000000..2ae2a09
--- /dev/null
+++ b/sys/kern/init_main.c
@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) 2023 Ian Marco Moffett and the VegaOS team.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of VegaOS nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/* $Id$ */
+
+#include <sys/cdefs.h>
+#include <sys/tty.h>
+#include <sys/syslog.h>
+#include <sys/machdep.h>
+#include <vm/vm_physseg.h>
+#include <logo.h>
+
+__KERNEL_META("$Vega$: init_main.c, Ian Marco Moffett, "
+              "Where the Vega kernel first starts up");
+
+static struct processor bsp = {
+    .gdtr = &g_early_gdtr,
+    .gdt  = &g_dmmy_gdt[0]
+};
+
+void
+main(void)
+{
+    tty_init();
+    syslog_init();
+    PRINT_LOGO();
+
+    processor_init(&bsp);
+    vm_physseg_init();
+
+    /* We're done here, halt the processor */
+    __ASMV("cli; hlt");
+}
diff --git a/sys/kern/kern_panic.c b/sys/kern/kern_panic.c
new file mode 100644
index 0000000..69680f7
--- /dev/null
+++ b/sys/kern/kern_panic.c
@@ -0,0 +1,58 @@
+/*
+ * Copyright (c) 2023 Ian Marco Moffett and the VegaOS team.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of VegaOS nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/* $Id$ */
+
+#include <sys/panic.h>
+#include <sys/syslog.h>
+#include <sys/machdep.h>
+
+/*
+ * Tells the user something terribly
+ * wrong happened then halting the system
+ * as soon as possible.
+ *
+ * XXX: There is no need to cleanup stuff here (e.g `va_list ap`)
+ *      as we won't be returning from here anyways and the source
+ *      of the panic could be *anywhere* so it's best not to mess with
+ *      things.
+ */
+void
+panic(const char *fmt, ...)
+{
+    va_list ap;
+
+    va_start(ap, fmt);
+
+    kprintf("panic: ");
+    vkprintf(fmt, &ap);
+
+    processor_halt();
+    __builtin_unreachable();
+}
diff --git a/sys/kern/kern_syslog.c b/sys/kern/kern_syslog.c
new file mode 100644
index 0000000..cd7f8f0
--- /dev/null
+++ b/sys/kern/kern_syslog.c
@@ -0,0 +1,96 @@
+/*
+ * Copyright (c) 2023 Ian Marco Moffett and the VegaOS team.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of VegaOS nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/* $Id$ */
+
+#include <sys/syslog.h>
+#include <sys/tty.h>
+#include <string.h>
+
+static struct tty syslog_tty;
+
+static void
+syslog_handle_fmt(va_list *ap, char fmt_spec)
+{
+    char tmp_ch;
+    int64_t tmp_int;
+    const char *tmp_str;
+    char tmp_buf[256] = { 0 };
+
+    switch (fmt_spec) {
+    case 'c':
+        tmp_ch = va_arg(*ap, int);
+        tty_write(&syslog_tty, &tmp_ch, 1);
+        break;
+    case 's':
+        tmp_str = va_arg(*ap, const char *);
+        tty_write(&syslog_tty, tmp_str, strlen(tmp_str));
+        break;
+    case 'd':
+        tmp_int = va_arg(*ap, int64_t);
+        itoa(tmp_int, tmp_buf, 10);
+        tty_write(&syslog_tty, tmp_buf, strlen(tmp_buf));
+        break;
+    case 'x':
+        tmp_int = va_arg(*ap, uint64_t);
+        itoa(tmp_int, tmp_buf, 16);
+        tty_write(&syslog_tty, tmp_buf + 2, strlen(tmp_buf) - 2);
+        break;
+    }
+}
+
+void
+vkprintf(const char *fmt, va_list *ap)
+{
+    while (*fmt) {
+        if (*fmt == '%') {
+            ++fmt;
+            syslog_handle_fmt(ap, *fmt++);
+        } else {
+            tty_write(&syslog_tty, fmt++, 1);
+        }
+    }
+}
+
+void
+kprintf(const char *fmt, ...)
+{
+    va_list ap;
+
+    va_start(ap, fmt);
+    vkprintf(fmt, &ap);
+    va_end(ap);
+}
+
+void
+syslog_init(void)
+{
+    tty_set_defaults(&syslog_tty);
+    tty_attach(&syslog_tty);
+}
diff --git a/sys/kern/tty.c b/sys/kern/tty.c
new file mode 100644
index 0000000..f166302
--- /dev/null
+++ b/sys/kern/tty.c
@@ -0,0 +1,387 @@
+/*
+ * Copyright (c) 2023 Ian Marco Moffett and the VegaOS team.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of VegaOS nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/* $Id$ */
+
+#include <sys/tty.h>
+#include <sys/cdefs.h>
+#include <sys/errno.h>
+#include <sys/ascii.h>
+#include <string.h>
+#include <tty_font.h>
+
+/*
+ * Default cursor color.
+ *
+ * TODO: The cursor color should
+ *       be the invert of the color
+ *       of whatever it is on top of.
+ */
+#define DEFAULT_CURSOR_BG 0x808080
+
+#define CURSOR_WIDTH            FONT_WIDTH
+#define CURSOR_HEIGHT           FONT_HEIGHT
+
+__KERNEL_META("$Vega$: tty.c, Ian Marco Moffett, "
+              "Core TTY implementation");
+
+/* List of attached TTYs */
+static TAILQ_HEAD(, tty) tty_list;
+
+/*
+ * Renders a char onto the
+ * TTY specified by `tty`.
+ */
+static void
+tty_draw_char(struct tty *tty, char c, uint32_t fg, uint32_t bg)
+{
+    uint32_t *fb_ptr;
+    uint32_t x, y;
+    size_t idx;
+    const uint8_t *glyph;
+
+    /* Get a pointer to framebuffer memory */
+    fb_ptr = tty->fbdev.mem;
+
+    /* Get the specific glyph of `c` */
+    glyph = &DEFAULT_FONT_DATA[(int)c*16];
+
+    x = tty->chpos_x;
+    y = tty->chpos_y;
+
+    for (uint32_t cy = 0; cy < FONT_HEIGHT; ++cy) {
+        for (uint32_t cx = 0; cx < FONT_WIDTH; ++cx) {
+            idx = fbdev_get_index(&tty->fbdev, x+FONT_WIDTH-cx, y+cy);
+            fb_ptr[idx] = __TEST(glyph[cy], __BIT(cx)) ? fg : bg;
+        }
+    }
+}
+
+/*
+ * Draws a cursor onto
+ * the screen.
+ *
+ * Call with TTY locked.
+ */
+static void
+tty_draw_cursor(struct tty *tty, bool hide)
+{
+    uint32_t x, y, idx;
+    uint32_t *fb_ptr;
+    uint32_t color;
+
+    fb_ptr = tty->fbdev.mem;
+    color = hide ? tty->bg : DEFAULT_CURSOR_BG;
+
+    for (size_t cy = 0; cy < CURSOR_HEIGHT; ++cy) {
+        for (size_t cx = 0; cx < CURSOR_WIDTH; ++cx) {
+            x = tty->curspos_x + cx;
+            y = tty->curspos_y + cy;
+            idx = fbdev_get_index(&tty->fbdev, x, y);
+            fb_ptr[idx] = color;
+        }
+    }
+}
+
+static void
+tty_scroll_single(struct tty *tty)
+{
+    uint32_t *fb_ptr;
+    size_t line_size, dest_idx, src_idx;
+
+    fb_ptr = tty->fbdev.mem;
+    line_size = tty->fbdev.pitch/4;
+
+    /* Copy each line up */
+    for (size_t y = FONT_HEIGHT; y < tty->t_ws_ypixel; y += FONT_HEIGHT) {
+        dest_idx = fbdev_get_index(&tty->fbdev, 0, y - FONT_HEIGHT);
+        src_idx = fbdev_get_index(&tty->fbdev, 0, y);
+        memcpy32(&fb_ptr[dest_idx], &fb_ptr[src_idx], FONT_HEIGHT*line_size);
+    }
+
+    /*
+     * Ensure we start at X position 0
+     * after we scrolled down.
+     */
+    tty->chpos_x = 0;
+    tty->curspos_x = 0;
+}
+
+/*
+ * Handles a newline.
+ *
+ * Call with TTY locked.
+ */
+static inline void
+tty_newline(struct tty *tty)
+{
+    uint32_t ypos;
+    const uint32_t MAX_YPOS = tty->t_ws_ypixel - (CURSOR_HEIGHT*2);
+
+    /* Hide the cursor */
+    tty_draw_cursor(tty, true);
+
+    /* Reset X positions */
+    tty->chpos_x = 0;
+    tty->curspos_x = 0;
+
+    /*
+     * Get the value closest to end
+     * of the screen.
+     */
+    ypos = __MAX(tty->chpos_y, tty->curspos_y);
+
+    /*
+     * Check if we need to scroll
+     * instead of incrementing
+     * Y positions.
+     */
+    if (ypos < MAX_YPOS) {
+        tty->chpos_y += FONT_HEIGHT;
+        tty->curspos_y += FONT_HEIGHT;
+    } else {
+        tty_scroll_single(tty);
+    }
+
+    /* Redraw the cursor */
+    tty_draw_cursor(tty, false);
+}
+
+/*
+ * Appends a character to the TTY specified
+ * by `tty` as well as incrementing tty->chpos_x
+ * and making newlines as needed.
+ *
+ * Call with TTY locked.
+ */
+static inline void
+tty_append_char(struct tty *tty, int c)
+{
+    const uint32_t MAX_XPOS = tty->t_ws_xpixel - FONT_WIDTH;
+
+    /* Hide the cursor */
+    tty_draw_cursor(tty, true);
+
+    tty_draw_char(tty, c, tty->fg, tty->bg);
+    tty->chpos_x += FONT_WIDTH;
+    tty->curspos_x += FONT_WIDTH;
+
+    if (tty->chpos_x >= MAX_XPOS) {
+        tty_newline(tty);
+    }
+
+    /* Redraw the cursor */
+    tty_draw_cursor(tty, false);
+}
+
+/*
+ * Writes out a tab as `tty->tab_width`
+ * spaces.
+ *
+ * Call with TTY locked.
+ */
+static void
+tty_expand_tab(struct tty *tty)
+{
+    for (size_t i = 0; i < tty->tab_width; ++i) {
+        tty_append_char(tty, ' ');
+    }
+}
+
+/*
+ * Writes a char to the TTY.
+ *
+ * Returns 0 on success; non-zero value
+ * is a character to be resent.
+ *
+ * Call with TTY locked.
+ */
+static int
+tty_putch(struct tty *tty, int c)
+{
+    if (!__TEST(tty->t_oflag, OPOST)) {
+        /*
+         * Just write out the char with
+         * no processing.
+         */
+        tty_append_char(tty, c);
+        return 0;
+    }
+
+    switch (c) {
+    case ASCII_HT:
+        /* Tab */
+        tty_expand_tab(tty);
+        break;
+    case ASCII_LF:
+        /* Line feed ('\n') */
+        tty_newline(tty);
+        break;
+    default:
+        tty_append_char(tty, c);
+        break;
+    }
+
+    return 0;
+}
+
+/*
+ * Flushes a TTY specified
+ * by `tty`.
+ *
+ * Call with TTY locked.
+ */
+void
+tty_flush(struct tty *tty)
+{
+    struct tty_ring *ring;
+
+    ring = &tty->ring;
+
+    /*
+     * Write each byte from the buffer
+     * to the screen with output processing
+     * if possible.
+     *
+     * XXX: Perhaps there could be a faster
+     *      way of doing this instead of
+     *      byte by byte?
+     */
+    for (size_t i = 0; i < ring->len; ++i) {
+        tty_putch(tty, ring->buf[i]);
+    }
+
+    ring->len = 0;
+}
+
+/*
+ * Writes to a TTY specified by `tty`.
+ *
+ * @buf: Buffer to write.
+ * @len: Length of buffer.
+ *
+ * Returns number of bytes written, and
+ * EXIT_FAILURE on error.
+ */
+ssize_t
+tty_write(struct tty *tty, const char *buf, size_t len)
+{
+    if (len == 0) {
+        /* Bad value, don't even try */
+        return EXIT_FAILURE;
+    }
+
+    TTY_LOCK(tty);
+    for (size_t i = 0; i < len; ++i) {
+        tty_push_char(tty, buf[i]);
+        /*
+         * If we have a newline and we are
+         * buffering bytes, flush the ring.
+         */
+        if (buf[i] == '\n' && __TEST(tty->t_oflag, ORBUF)) {
+            tty_flush(tty);
+        }
+    }
+
+    /*
+     * If we aren't buffering bytes, don't
+     * keep the bytes within the ring and
+     * flush it right away per `tty_write()`
+     * call.
+     */
+    if (!__TEST(tty->t_oflag, ORBUF)) {
+        tty_flush(tty);
+    }
+
+    TTY_UNLOCK(tty);
+    return len;
+}
+
+/*
+ * Sets TTY fields to their defaults.
+ */
+void
+tty_set_defaults(struct tty *tty)
+{
+    /* Ensure everything is initially zero */
+    memset(tty, 0, sizeof(*tty));
+
+    /*
+     * Now, initialize everything to their defaults.
+     *
+     * Some notes about the default framebuffer device:
+     * ------------------------------------------------
+     *  The default framebuffer device should be the
+     *  front buffer. Later on during boot, all attached
+     *  TTYs shall have their fbdev swapped out with a
+     *  backbuffer to improve performace as reading directly
+     *  from video memory is going to be slow.
+     *
+     *  XXX: At some point we should be allocating a backbuffer
+     *       instead when it's time for *all* TTYs to have them.
+     *
+     *       A good idea would be to only allocate a backbuffer
+     *       *if* we switched to some TTY and deallocate
+     *       that backbuffer when switching away from that TTY.
+     *
+     *       The first thing that comes to mind when thinking
+     *       about this idea is loosing our text when we switch
+     *       back out. To rectify this, we could buffer chars
+     *       which would take less memory than keeping the whole
+     *       backbuffer (holds pixels i.e uint32_t).
+     *
+     *       This can perhaps be done by some internal flag which
+     *       indicates that kmalloc() is usable and chars can
+     *       be buffered. Once we switch back, just allocate
+     *       a new backbuffer and copy the chars back.
+     */
+    tty->fbdev = fbdev_get_front();
+    tty->t_oflag = (OPOST | ORBUF);
+    tty->tab_width = DEFAULT_TAB_WIDTH;
+    tty->fg = 0x808080;
+    tty->bg = 0x000000;
+    tty->t_ws_xpixel = tty->fbdev.width;
+    tty->t_ws_ypixel = tty->fbdev.height;
+    tty->t_ws_row = tty->fbdev.height / FONT_HEIGHT;
+    tty->t_ws_col = tty->fbdev.width / FONT_WIDTH;
+
+}
+
+void
+tty_attach(struct tty *tty)
+{
+    TAILQ_INSERT_TAIL(&tty_list, tty, link);
+    tty_draw_cursor(tty, false);
+}
+
+void
+tty_init(void)
+{
+    TAILQ_INIT(&tty_list);  /* Ensure the TTY list is usable */
+}
diff --git a/sys/kern/tty_subr.c b/sys/kern/tty_subr.c
new file mode 100644
index 0000000..4c8405e
--- /dev/null
+++ b/sys/kern/tty_subr.c
@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) 2023 Ian Marco Moffett and the VegaOS team.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of VegaOS nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/* $Id$ */
+
+#include <sys/tty.h>
+
+/*
+ * Pushes a char to the TTY
+ * ring buffer.
+ *
+ * Call with TTY locked.
+ */
+void
+tty_push_char(struct tty *tty, int c)
+{
+    struct tty_ring *ring;
+
+    ring = &tty->ring;
+
+    /*
+     * If our ring is full, it should
+     * be flushed as soon as possible.
+     *
+     * XXX: ring->len will be reset by tty_flush()
+     * so there is no need to do it here.
+     */
+    if (ring->len >= LINE_RING_SIZE) {
+        tty_flush(tty);
+    }
+
+    ring->buf[ring->len++] = c;
+}