From 3980f6c5b6a637a290939ed53f00894d3aaa97b1 Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Tue, 14 May 2024 00:17:03 -0400
Subject: kernel: tty: Add tty_attach()

This commit adds a new routine called tty_attach(). This routine allows
a TTY to be registered with the system and have a device file associated
with it.

Signed-off-by: Ian Moffett <ian@osmora.org>
---
 sys/include/sys/tty.h |  4 +++
 sys/kern/init_main.c  |  6 +++++
 sys/kern/kern_tty.c   | 67 +++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 77 insertions(+)

(limited to 'sys')

diff --git a/sys/include/sys/tty.h b/sys/include/sys/tty.h
index 2700abc..4a2c9ec 100644
--- a/sys/include/sys/tty.h
+++ b/sys/include/sys/tty.h
@@ -33,6 +33,7 @@
 #include <sys/types.h>
 #include <sys/termios.h>
 #include <sys/spinlock.h>
+#include <sys/device.h>
 #include <dev/vcons/vcons.h>
 
 #define TTY_RING_SIZE 32
@@ -44,14 +45,17 @@ struct tty_ring {
 };
 
 struct tty {
+    dev_t id;
     struct vcons_screen *scr;   /* Console screen */
     struct tty_ring ring;       /* Input ring */
     struct spinlock rlock;      /* Ring lock */
     struct termios termios;     /* Termios structure */
+    struct device *dev;         /* Device pointer */
 };
 
 extern struct tty g_root_tty;
 
+dev_t tty_attach(struct tty *tty);
 int tty_putc(struct tty *tty, int c);
 ssize_t tty_flush(struct tty *tty);
 
diff --git a/sys/kern/init_main.c b/sys/kern/init_main.c
index c78d401..5a0a64b 100644
--- a/sys/kern/init_main.c
+++ b/sys/kern/init_main.c
@@ -32,6 +32,7 @@
 #include <sys/machdep.h>
 #include <sys/timer.h>
 #include <sys/sched.h>
+#include <sys/tty.h>
 #include <sys/vfs.h>
 #include <sys/driver.h>
 #include <machine/cpu_mp.h>
@@ -76,6 +77,7 @@ void
 main(void)
 {
     struct cpu_info *ci;
+    int status;
 
     __TRY_CALL(pre_init);
     syslog_init();
@@ -93,6 +95,10 @@ main(void)
 
     vfs_init();
 
+    /* Attach the root TTY */
+    if ((status = tty_attach(&g_root_tty)) < 0)
+        kprintf("Failed to attach root TTY (got %d)\n", status);
+
     DRIVERS_INIT();
 
     sched_init();
diff --git a/sys/kern/kern_tty.c b/sys/kern/kern_tty.c
index 146ace0..39b94f7 100644
--- a/sys/kern/kern_tty.c
+++ b/sys/kern/kern_tty.c
@@ -31,7 +31,10 @@
 #include <sys/cdefs.h>
 #include <sys/errno.h>
 #include <sys/syslog.h>
+#include <fs/devfs.h>
+#include <string.h>
 
+static dev_t tty_major = 0;
 struct tty g_root_tty = {
     .scr = &g_syslog_screen,
     .ring = {
@@ -40,6 +43,14 @@ struct tty g_root_tty = {
     }
 };
 
+static inline dev_t
+tty_alloc_id(void)
+{
+    static dev_t id = 1;
+
+    return id++;
+}
+
 /*
  * Flushes the TTY ring buffer.
  *
@@ -70,6 +81,33 @@ __tty_flush(struct tty *tty)
     return count;
 }
 
+/*
+ * Device structure routine for reading a
+ * TTY device file.
+ */
+static int
+tty_dev_read(struct device *dev, struct sio_txn *sio)
+{
+    struct tty_ring *ring = &g_root_tty.ring;
+    size_t len;
+
+    spinlock_acquire(&g_root_tty.rlock);
+    len = (ring->enq_index - ring->deq_index);
+
+    /*
+     * Transfer data from the TTY ring with SIO and
+     * flush it.
+     *
+     * TODO: As of now we are just reading the root
+     *       TTY, add support for multiple TTYs.
+     */
+    memcpy(sio->buf, ring->data, len);
+    __tty_flush(&g_root_tty);
+
+    spinlock_release(&g_root_tty.rlock);
+    return len;
+}
+
 /*
  * Serialized wrapper over __tty_flush()
  */
@@ -106,3 +144,32 @@ tty_putc(struct tty *tty, int c)
     spinlock_release(&tty->rlock);
     return 0;
 }
+
+dev_t
+tty_attach(struct tty *tty)
+{
+    int tmp;
+    char devname[128];
+    struct device *dev = device_alloc();
+
+    if (dev == NULL)
+        return -ENOMEM;
+
+    /*
+     * Allocate a major for the driver if we don't
+     * have one yet.
+     */
+    if (tty_major == 0)
+        tty_major = device_alloc_major();
+
+    /* Now try to create the device */
+    tty->id = tty_alloc_id();
+    if ((tmp = device_create(dev, tty_major, tty->id)) < 0)
+        return tmp;
+
+    dev->read = tty_dev_read;
+    dev->blocksize = 1;
+
+    snprintf(devname, sizeof(devname), "tty%d", tty->id);
+    return devfs_add_dev(devname, dev);
+}
-- 
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