consoles: polling support, kgdboc

polled console handling support, to access a console in an irq-less
way while in debug or irq context.

absolutely zero impact as long as CONFIG_CONSOLE_POLL is disabled.
(which is the default)

[ jan.kiszka@siemens.com: lots of cleanups ]
[ mingo@elte.hu: redesign, splitups, cleanups. ]

Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Jan Kiszka <jan.kiszka@web.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 47 insertions, 0 deletions

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index 613ec816ce60..4d3c7018f0c3 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -1155,6 +1155,48 @@ static struct tty_driver *get_tty_driver(dev_t device, int *index)
         return NULL;
 }
 
+#ifdef CONFIG_CONSOLE_POLL
+
+/**
+ *      tty_find_polling_driver -       find device of a polled tty
+ *      @name: name string to match
+ *      @line: pointer to resulting tty line nr
+ *
+ *      This routine returns a tty driver structure, given a name
+ *      and the condition that the tty driver is capable of polled
+ *      operation.
+ */
+struct tty_driver *tty_find_polling_driver(char *name, int *line)
+{
+        struct tty_driver *p, *res = NULL;
+        int tty_line = 0;
+        char *str;
+
+        mutex_lock(&tty_mutex);
+        /* Search through the tty devices to look for a match */
+        list_for_each_entry(p, &tty_drivers, tty_drivers) {
+                str = name + strlen(p->name);
+                tty_line = simple_strtoul(str, &str, 10);
+                if (*str == ',')
+                        str++;
+                if (*str == '\0')
+                        str = 0;
+
+                if (tty_line >= 0 && tty_line <= p->num && p->poll_init &&
+                                !p->poll_init(p, tty_line, str)) {
+
+                        res = p;
+                        *line = tty_line;
+                        break;
+                }
+        }
+        mutex_unlock(&tty_mutex);
+
+        return res;
+}
+EXPORT_SYMBOL_GPL(tty_find_polling_driver);
+#endif
+
 /**
  *      tty_check_change        -       check for POSIX terminal changes
  *      @tty: tty to check
@@ -3850,6 +3892,11 @@ void tty_set_operations(struct tty_driver *driver,
         driver->write_proc = op->write_proc;
         driver->tiocmget = op->tiocmget;
         driver->tiocmset = op->tiocmset;
+#ifdef CONFIG_CONSOLE_POLL
+        driver->poll_init = op->poll_init;
+        driver->poll_get_char = op->poll_get_char;
+        driver->poll_put_char = op->poll_put_char;
+#endif
 }