Removed the sys_puts system call in favour of calls to tty_write().

Removed the rsputs() function in favour of calls to tty_write().

Corrected a bug in the serial driver and TTY subsystem where a full
buffer wouldn't be detected. This was caused by a missing set of
brackets on several operations involving the modulus operator.

Added the ability for the serial driver to automatically take data from
the TTY device's write buffer and push it to the serial port. This can
happen in one of two ways; 1) the TTY subsystem notifies the serial
driver of new data by calling the write() function pointer in the
tty_struct or, 2) the serial port issues an interrupt signalling that it
has finished sending data prompting the driver to check the buffers for
any more pending data.

4 files changed, 47 insertions, 53 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index da55fa3..a17b58c 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -209,7 +209,7 @@ void sched_init(void) {
   ctask = NULL;
 
   create_proc(&_usrbin_start, (size_t) &_usrbin_size);
-  create_proc(&_usrbin_start, (size_t) &_usrbin_size);
+  /* create_proc(&_usrbin_start, (size_t) &_usrbin_size); */
 
   switch_to(0, &tasks[0]);
 }
diff --git a/kernel/serial.c b/kernel/serial.c
index a133865..e712e53 100644
--- a/kernel/serial.c
+++ b/kernel/serial.c
@@ -11,6 +11,9 @@
 /* 115200 baud */
 #define DIVISOR 1
 
+/* this shouldn't change */
+#define FIFOSZ 16
+
 #define RSBASE 0x3F8
 
 #define RSDATA    RSBASE
@@ -23,9 +26,6 @@
 #define RSMODEMS  (RSBASE + 6)
 #define RSSCRATCH (RSBASE + 7)
 
-#define rswait()\
-  while((inb(RSLINES) & 0x20) == 0);
-
 extern void rs_isr(void);
 
 /* internal function prototypes */
@@ -38,25 +38,6 @@ struct tty_struct tty_rs = {
 
 static char present;
 
-int rsputs(char *s) {
-  if(!present)
-    return -ENXIO;
-
-  while(*s) {
-    rswait();
-    if(*s == '\n' || *s == '\r') {
-      outb(RSDATA, '\n');
-      rswait();
-      outb(RSDATA, '\r');
-      s++;
-    } else {
-      outb(RSDATA, *s++);
-    }
-  }
-
-  return 0;
-}
-
 void serial_init(void) {
   present = 0;
 
@@ -91,7 +72,6 @@ void serial_init(void) {
   register_isr(0x24, 0, &rs_isr);
   irq_enable(0x10);
 
-  rsputs("[kernel] Serial monitor initialized!\n\r");
   printk("[rs] Serial port COM0 initialized!\n");
 
   present = 1;
@@ -102,22 +82,46 @@ void rsint_rx(void) {
 
   if((inb(RSLINES) & 1) == 0)
     return;
-  if(q->pwrite == (q->pread - 1 % sizeof(q->buf)))
+  if(q->pwrite == ((q->pread - 1) % sizeof(q->buf)))
     return;
 
   q->buf[q->pwrite] = inb(RSDATA);
-  q->pwrite = q->pwrite + 1 % sizeof(q->buf);
+  q->pwrite = (q->pwrite + 1) % sizeof(q->buf);
 
   wake_up(&q->waiting);
 }
 
+/*
+ * void rsint_tx(void) {
+ *   int copied = 0;
+ *   struct tty_queue *q = &tty_rs.wqueue;
+ *
+ *   while(q->pread != q->pwrite) {
+ *     [> we're done if the TX FIFO is full <]
+ *     if((inb(RSLINES) & 0x20) == 0)
+ *       break;
+ *
+ *     outb(RSDATA, q->buf[q->pread]);
+ *     q->pread = (q->pread + 1) % TTY_BUF_SIZE;
+ *
+ *     copied = 1;
+ *   }
+ *
+ *   if(copied)
+ *     wake_up(&q->waiting);
+ * }
+ */
+
 void rsint_tx(void) {
+  int i;
   int copied = 0;
   struct tty_queue *q = &tty_rs.wqueue;
 
-  while(q->pread != q->pwrite) {
-    /* we're done if the TX FIFO is full */
-    if((inb(RSLINES) & 0x20) == 0)
+  if((inb(RSLINES) & 0x20) == 0)
+    return;
+
+  for(i = 0; i < FIFOSZ; i++) {
+    if(q->pread == q->pwrite)
       break;
 
     outb(RSDATA, q->buf[q->pread]);
diff --git a/kernel/sys.c b/kernel/sys.c
index 8e28edd..b750072 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -11,26 +11,6 @@
 #include <time.h>
 #include <unistd.h>
 
-int sys_puts(char *s) {
-  char buf[8];
-
-  if(ctask->ctty < 0)
-    return EOF;
-
-  sprintf(buf, "[%04x] ", ctask->pid);
-
-  switch(ctask->ctty) {
-    case 1:
-      /* rsputs(buf); */
-      return rsputs(s);
-      break;
-    default:
-      printk("%s", buf);
-      return printk(s);
-      break;
-  }
-}
-
 time_t sys_time(void) {
   return ticks / 100;
 }
diff --git a/kernel/tty.c b/kernel/tty.c
index 75c3701..bfbf775 100644
--- a/kernel/tty.c
+++ b/kernel/tty.c
@@ -35,14 +35,24 @@ static int sleep_while_empty(struct tty_queue *q) {
 }
 
 /* check if a buffer's full and if so, go to sleep */
-static int sleep_while_full(struct tty_queue *q) {
+static int sleep_while_full(struct tty_queue *q, struct tty_struct *tty) {
   cli();
   while(1) {
-    if(q->pwrite == (q->pread - 1 % sizeof(q->buf)))
+    /*
+     * if the buffer is full, first notify the
+     * driver so it can try to remove some
+     * data then, check again and if it's
+     * still full, go to sleep.
+     */
+    if(q->pwrite == ((q->pread - 1) % sizeof(q->buf)))
+      if(tty->write)
+        tty->write();
+
+    if(q->pwrite == ((q->pread - 1) % sizeof(q->buf)))
       interruptible_sleep_on(&q->waiting);
 
     /* check again to see if anything was removed, or we were interrupted */
-    if(q->pwrite == (q->pread - 1 % sizeof(q->buf))) {
+    if(q->pwrite == ((q->pread - 1) % sizeof(q->buf))) {
       sti();
       return -1;
     }
@@ -98,7 +108,7 @@ ssize_t tty_write(unsigned tty, void *buf, size_t len) {
 
   for(i = 0; i < len; i++) {
     /* check if the buffer's full and if so, go to sleep */
-    if(sleep_while_full(q) < 0) {
+    if(sleep_while_full(q, ttys[tty]) < 0) {
       if(i == 0)
         return -EINTR;