DM: separate pty vuart operation from IOC

for pty vuart operation will be commonly used by other module,
like pm-vuart: control UOS power off through vuart.

Tracked-On: #3564
Signed-off-by: Minggui Cao <minggui.cao@intel.com>
Acked-by: Yin Fengwei <fengwei.yin@intel.com>

devicemodel/hw/platform/pty_vuart.c

@@ -0,0 +1,96 @@
+/*
+ * Project Acrn
+ * Acrn-dm-pty
+ *
+ * Copyright (C) 2019 Intel Corporation. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <dirent.h>
+#include <termios.h>
+#include <stdbool.h>
+#include <libgen.h>
+
+#include "log.h"
+
+/*
+ * Check and create the directory.
+ * To avoid symlink failure if the directory does not exist.
+ */
+static int check_dir(const char *file)
+{
+	char *tmp, *dir;
+
+	tmp = strdup(file);
+	if (!tmp) {
+		pr_err("failed to dup file, error:%s\n", strerror(errno));
+		return -1;
+	}
+
+	dir = dirname(tmp);
+	if (access(dir, F_OK) && mkdir(dir, 0666)) {
+		pr_err("failed to create dir:%s, erorr:%s\n", dir, strerror(errno));
+		free(tmp);
+		return -1;
+	}
+	free(tmp);
+	return 0;
+}
+
+/*
+ * Open PTY master device to used by caller and the PTY slave device for virtual
+ * UART. The pair(master/slave) can work as a communication channel between
+ * the caller and virtual UART.
+ */
+int pty_open_virtual_uart(const char *dev_name)
+{
+	int fd;
+	char *slave_name;
+	struct termios attr;
+
+	fd = open("/dev/ptmx", O_RDWR | O_NOCTTY | O_NONBLOCK);
+	if (fd < 0)
+		goto open_err;
+	if (grantpt(fd) < 0)
+		goto pty_err;
+	if (unlockpt(fd) < 0)
+		goto pty_err;
+	slave_name = ptsname(fd);
+	if (!slave_name)
+		goto pty_err;
+	if ((unlink(dev_name) < 0) && errno != ENOENT)
+		goto pty_err;
+	/*
+	 * The check_dir restriction is that only create one directory
+	 * not support multi-level directroy.
+	 */
+	if (check_dir(dev_name) < 0)
+		goto pty_err;
+	if (symlink(slave_name, dev_name) < 0)
+		goto pty_err;
+	if (chmod(dev_name, 0660) < 0)
+		goto attr_err;
+	if (tcgetattr(fd, &attr) < 0)
+		goto attr_err;
+	cfmakeraw(&attr);
+	attr.c_cflag |= CLOCAL;
+	if (tcsetattr(fd, TCSANOW, &attr) < 0)
+		goto attr_err;
+	return fd;
+
+attr_err:
+	unlink(dev_name);
+pty_err:
+	close(fd);
+open_err:
+	return -1;
+}