sandbox: Restore blocking I/O on exit

At present sandbox sets non-blocking I/O as soon as any input is read
from the terminal. However it does not restore the previous state on
exit. Fix this and drop the old os_read_no_block() function.

This means that we always enable blocking I/O in sandbox (if input is a
terminal) whereas previously it would only happen on the first call to
tstc() or getc(). However, the difference is likely not important.

Signed-off-by: Simon Glass <sjg@chromium.org>

arch/sandbox/cpu/os.c

@@ -38,14 +38,6 @@ ssize_t os_read(int fd, void *buf, size_t count)
 	return read(fd, buf, count);
 }
 
-ssize_t os_read_no_block(int fd, void *buf, size_t count)
-{
-	const int flags = fcntl(fd, F_GETFL, 0);
-
-	fcntl(fd, F_SETFL, flags | O_NONBLOCK);
-	return os_read(fd, buf, count);
-}
-
 ssize_t os_write(int fd, const void *buf, size_t count)
 {
 	return write(fd, buf, count);
@@ -129,11 +121,18 @@ int os_write_file(const char *name, const void *buf, int size)
 /* Restore tty state when we exit */
 static struct termios orig_term;
 static bool term_setup;
+static bool term_nonblock;
 
 void os_fd_restore(void)
 {
 	if (term_setup) {
+		int flags;
+
 		tcsetattr(0, TCSANOW, &orig_term);
+		if (term_nonblock) {
+			flags = fcntl(0, F_GETFL, 0);
+			fcntl(0, F_SETFL, flags & ~O_NONBLOCK);
+		}
 		term_setup = false;
 	}
 }
@@ -142,6 +141,7 @@ void os_fd_restore(void)
 void os_tty_raw(int fd, bool allow_sigs)
 {
 	struct termios term;
+	int flags;
 
 	if (term_setup)
 		return;
@@ -158,6 +158,13 @@ void os_tty_raw(int fd, bool allow_sigs)
 	if (tcsetattr(fd, TCSANOW, &term))
 		return;
 
+	flags = fcntl(fd, F_GETFL, 0);
+	if (!(flags & O_NONBLOCK)) {
+		if (fcntl(fd, F_SETFL, flags | O_NONBLOCK))
+			return;
+		term_nonblock = true;
+	}
+
 	term_setup = true;
 	atexit(os_fd_restore);
 }

drivers/serial/sandbox.c

@@ -126,7 +126,7 @@ static int sandbox_serial_pending(struct udevice *dev, bool input)
 	if (next_index == serial_buf_read)
 		return 1;	/* buffer full */
 
-	count = os_read_no_block(0, &serial_buf[serial_buf_write], 1);
+	count = os_read(0, &serial_buf[serial_buf_write], 1);
 	if (count == 1)
 		serial_buf_write = next_index;
 

include/os.h

@@ -26,16 +26,6 @@ struct sandbox_state;
  */
 ssize_t os_read(int fd, void *buf, size_t count);
 
-/**
- * Access to the OS read() system call with non-blocking access
- *
- * \param fd	File descriptor as returned by os_open()
- * \param buf	Buffer to place data
- * \param count	Number of bytes to read
- * \return number of bytes read, or -1 on error
- */
-ssize_t os_read_no_block(int fd, void *buf, size_t count);
-
 /**
  * Access to the OS write() system call
  *