hvc_console: Add kdb support

Add poll_get_char and poll_put_char for kdb. Enable kdb at boot with:

kgdboc=hvc0

or at runtime with:

echo hvc0 > /sys/module/kgdboc/parameters/kgdboc

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 39 insertions, 0 deletions

diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c
index 59000750cc73..e1aaf4f309b3 100644
--- a/drivers/tty/hvc/hvc_console.c
+++ b/drivers/tty/hvc/hvc_console.c
@@ -39,6 +39,7 @@
 #include <linux/delay.h>
 #include <linux/freezer.h>
 #include <linux/slab.h>
+#include <linux/serial_core.h>
 
 #include <asm/uaccess.h>
 
@@ -766,6 +767,39 @@ static int hvc_tiocmset(struct tty_struct *tty,
         return hp->ops->tiocmset(hp, set, clear);
 }
 
+#ifdef CONFIG_CONSOLE_POLL
+int hvc_poll_init(struct tty_driver *driver, int line, char *options)
+{
+        return 0;
+}
+
+static int hvc_poll_get_char(struct tty_driver *driver, int line)
+{
+        struct tty_struct *tty = driver->ttys[0];
+        struct hvc_struct *hp = tty->driver_data;
+        int n;
+        char ch;
+
+        n = hp->ops->get_chars(hp->vtermno, &ch, 1);
+
+        if (n == 0)
+                return NO_POLL_CHAR;
+
+        return ch;
+}
+
+static void hvc_poll_put_char(struct tty_driver *driver, int line, char ch)
+{
+        struct tty_struct *tty = driver->ttys[0];
+        struct hvc_struct *hp = tty->driver_data;
+        int n;
+
+        do {
+                n = hp->ops->put_chars(hp->vtermno, &ch, 1);
+        } while (n <= 0);
+}
+#endif
+
 static const struct tty_operations hvc_ops = {
         .open = hvc_open,
         .close = hvc_close,
@@ -776,6 +810,11 @@ static const struct tty_operations hvc_ops = {
         .chars_in_buffer = hvc_chars_in_buffer,
         .tiocmget = hvc_tiocmget,
         .tiocmset = hvc_tiocmset,
+#ifdef CONFIG_CONSOLE_POLL
+        .poll_init = hvc_poll_init,
+        .poll_get_char = hvc_poll_get_char,
+        .poll_put_char = hvc_poll_put_char,
+#endif
 };
 
 struct hvc_struct *hvc_alloc(uint32_t vtermno, int data,