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, 163 insertions, 0 deletions

diff --git a/drivers/serial/kgdboc.c b/drivers/serial/kgdboc.c
new file mode 100644
index 000000000000..341830791608
--- /dev/null
+++ b/drivers/serial/kgdboc.c
@@ -0,0 +1,163 @@
+/*
+ * Based on the same principle as kgdboe using the NETPOLL api, this
+ * driver uses a console polling api to implement a gdb serial inteface
+ * which is multiplexed on a console port.
+ *
+ * Maintainer: Jason Wessel <jason.wessel@windriver.com>
+ *
+ * 2007-2008 (c) Jason Wessel - Wind River Systems, Inc.
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2. This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+#include <linux/kernel.h>
+#include <linux/ctype.h>
+#include <linux/kgdb.h>
+#include <linux/tty.h>
+
+#define MAX_CONFIG_LEN          40
+
+static struct kgdb_io           kgdboc_io_ops;
+
+/* -1 = init not run yet, 0 = unconfigured, 1 = configured. */
+static int configured           = -1;
+
+static char config[MAX_CONFIG_LEN];
+static struct kparam_string kps = {
+        .string                 = config,
+        .maxlen                 = MAX_CONFIG_LEN,
+};
+
+static struct tty_driver        *kgdb_tty_driver;
+static int                      kgdb_tty_line;
+
+static int kgdboc_option_setup(char *opt)
+{
+        if (strlen(opt) > MAX_CONFIG_LEN) {
+                printk(KERN_ERR "kgdboc: config string too long\n");
+                return -ENOSPC;
+        }
+        strcpy(config, opt);
+
+        return 0;
+}
+
+__setup("kgdboc=", kgdboc_option_setup);
+
+static int configure_kgdboc(void)
+{
+        struct tty_driver *p;
+        int tty_line = 0;
+        int err;
+
+        err = kgdboc_option_setup(config);
+        if (err || !strlen(config) || isspace(config[0]))
+                goto noconfig;
+
+        err = -ENODEV;
+
+        p = tty_find_polling_driver(config, &tty_line);
+        if (!p)
+                goto noconfig;
+
+        kgdb_tty_driver = p;
+        kgdb_tty_line = tty_line;
+
+        err = kgdb_register_io_module(&kgdboc_io_ops);
+        if (err)
+                goto noconfig;
+
+        configured = 1;
+
+        return 0;
+
+noconfig:
+        config[0] = 0;
+        configured = 0;
+
+        return err;
+}
+
+static int __init init_kgdboc(void)
+{
+        /* Already configured? */
+        if (configured == 1)
+                return 0;
+
+        return configure_kgdboc();
+}
+
+static void cleanup_kgdboc(void)
+{
+        if (configured == 1)
+                kgdb_unregister_io_module(&kgdboc_io_ops);
+}
+
+static int kgdboc_get_char(void)
+{
+        return kgdb_tty_driver->poll_get_char(kgdb_tty_driver, kgdb_tty_line);
+}
+
+static void kgdboc_put_char(u8 chr)
+{
+        kgdb_tty_driver->poll_put_char(kgdb_tty_driver, kgdb_tty_line, chr);
+}
+
+static int param_set_kgdboc_var(const char *kmessage, struct kernel_param *kp)
+{
+        if (strlen(kmessage) >= MAX_CONFIG_LEN) {
+                printk(KERN_ERR "kgdboc: config string too long\n");
+                return -ENOSPC;
+        }
+
+        /* Only copy in the string if the init function has not run yet */
+        if (configured < 0) {
+                strcpy(config, kmessage);
+                return 0;
+        }
+
+        if (kgdb_connected) {
+                printk(KERN_ERR
+                       "kgdboc: Cannot reconfigure while KGDB is connected.\n");
+
+                return -EBUSY;
+        }
+
+        strcpy(config, kmessage);
+
+        if (configured == 1)
+                cleanup_kgdboc();
+
+        /* Go and configure with the new params. */
+        return configure_kgdboc();
+}
+
+static void kgdboc_pre_exp_handler(void)
+{
+        /* Increment the module count when the debugger is active */
+        if (!kgdb_connected)
+                try_module_get(THIS_MODULE);
+}
+
+static void kgdboc_post_exp_handler(void)
+{
+        /* decrement the module count when the debugger detaches */
+        if (!kgdb_connected)
+                module_put(THIS_MODULE);
+}
+
+static struct kgdb_io kgdboc_io_ops = {
+        .name                   = "kgdboc",
+        .read_char              = kgdboc_get_char,
+        .write_char             = kgdboc_put_char,
+        .pre_exception          = kgdboc_pre_exp_handler,
+        .post_exception         = kgdboc_post_exp_handler,
+};
+
+module_init(init_kgdboc);
+module_exit(cleanup_kgdboc);
+module_param_call(kgdboc, param_set_kgdboc_var, param_get_string, &kps, 0644);
+MODULE_PARM_DESC(kgdboc, "<serial_device>[,baud]");
+MODULE_DESCRIPTION("KGDB Console TTY Driver");
+MODULE_LICENSE("GPL");