Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/geert/linux...

[firefly-linux-kernel-4.4.55.git] / drivers / tty / hvc / hvc_dcc.c

diff --git a/drivers/tty/hvc/hvc_dcc.c b/drivers/tty/hvc/hvc_dcc.c
index 44fbebab5075f98f337d880288993b01ad9e7271..3502a7bbb69eee716f21b5b5b89c14fd3f9627fb 100644 (file)
--- a/drivers/tty/hvc/hvc_dcc.c
+++ b/drivers/tty/hvc/hvc_dcc.c
@@ -86,6 +86,21 @@ static int hvc_dcc_get_chars(uint32_t vt, char *buf, int count)
        return i;
 }
 
+static bool hvc_dcc_check(void)
+{
+       unsigned long time = jiffies + (HZ / 10);
+
+       /* Write a test character to check if it is handled */
+       __dcc_putchar('\n');
+
+       while (time_is_after_jiffies(time)) {
+               if (!(__dcc_getstatus() & DCC_STATUS_TX))
+                       return true;
+       }
+
+       return false;
+}
+
 static const struct hv_ops hvc_dcc_get_put_ops = {
        .get_chars = hvc_dcc_get_chars,
        .put_chars = hvc_dcc_put_chars,
@@ -93,6 +108,9 @@ static const struct hv_ops hvc_dcc_get_put_ops = {
 
 static int __init hvc_dcc_console_init(void)
 {
+       if (!hvc_dcc_check())
+               return -ENODEV;
+
        hvc_instantiate(0, 0, &hvc_dcc_get_put_ops);
        return 0;
 }
@@ -100,6 +118,9 @@ console_initcall(hvc_dcc_console_init);
 
 static int __init hvc_dcc_init(void)
 {
+       if (!hvc_dcc_check())
+               return -ENODEV;
+
        hvc_alloc(0, 0, &hvc_dcc_get_put_ops, 128);
        return 0;
 }