kernel: tty: Add initial TTY code

Signed-off-by: Ian Moffett <ian@osmora.org>

1 files changed, 108 insertions, 0 deletions

diff --git a/sys/kern/kern_tty.c b/sys/kern/kern_tty.c
new file mode 100644
index 0000000..146ace0
--- /dev/null
+++ b/sys/kern/kern_tty.c
@@ -0,0 +1,108 @@
+/*
+ * Copyright (c) 2023-2024 Ian Marco Moffett and the Osmora 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 Hyra 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.
+ */
+
+#include <sys/tty.h>
+#include <sys/cdefs.h>
+#include <sys/errno.h>
+#include <sys/syslog.h>
+
+struct tty g_root_tty = {
+    .scr = &g_syslog_screen,
+    .ring = {
+        .enq_index = 0,
+        .deq_index = 0,
+    }
+};
+
+/*
+ * Flushes the TTY ring buffer.
+ *
+ * @tty: TTY to flush.
+ *
+ * Returns number of bytes flushed.
+ */
+static ssize_t
+__tty_flush(struct tty *tty)
+{
+    struct tty_ring *ring = &tty->ring;
+    size_t count = 0;
+    char tmp;
+
+    /* Do we have any data left? */
+    if (ring->deq_index >= ring->enq_index)
+        return -EAGAIN;
+
+    /* Flush the ring */
+    while (ring->deq_index < ring->enq_index) {
+        tmp = ring->data[ring->deq_index++];
+        vcons_putch(tty->scr, tmp);
+        ++count;
+    }
+
+    ring->enq_index = 0;
+    ring->deq_index = 0;
+    return count;
+}
+
+/*
+ * Serialized wrapper over __tty_flush()
+ */
+ssize_t
+tty_flush(struct tty *tty)
+{
+    ssize_t ret;
+
+    spinlock_acquire(&tty->rlock);
+    ret = __tty_flush(tty);
+    spinlock_release(&tty->rlock);
+    return ret;
+}
+
+/*
+ * Write a character to a TTY
+ *
+ * @tty: TTY to write to.
+ * @c: Character to write.
+ */
+int
+tty_putc(struct tty *tty, int c)
+{
+    struct tty_ring *ring;
+
+    ring = &tty->ring;
+    spinlock_acquire(&tty->rlock);
+
+    if (ring->enq_index >= TTY_RING_SIZE) {
+        __tty_flush(tty);
+    }
+
+    ring->data[ring->enq_index++] = c;
+    spinlock_release(&tty->rlock);
+    return 0;
+}