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Date: Tue, 21 Oct 2008 14:14:51 -0500
From: Jason Wessel <jason.wessel@...driver.com>
To: kgdb-bugreport@...ts.sourceforge.net
Cc: linux-kernel@...r.kernel.org,
Jason Wessel <jason.wessel@...driver.com>,
alan@...rguk.ukuu.org.uk
Subject: [PATCH 5/7] kgdboc, tty: use tty open to start low level drivers
This patch adds two new hooks to the tty layer in tty_io.c to allow
kgdboc to open a tty prior to the start of the user space processes,
as well as to open a tty to serial port which has nothing connected on
it. This is for the purpose of starting the low level serial drivers
such that a control-c can be caught via the RX poll mechanism.
The two new functions, tty_console_poll_open() and
tty_console_poll_close() take care of setting/cleaning up an empty
"struct file *filp" as well as keeping the reference counts correct
for the tty device. The new function are only accessible if
CONFIG_CONSOLE_POLL as it is a direct extension to the console poll
API. All the filp operation for the new functions take place in the
tty_io.c so no further functions have to be exported externally as
well as allowing for the internals of the tty layer to remain private.
A few minor changes were needed in tty_io.c to deal with the fact that
the inode and fpath.dentry were NULL with the generic flip structure.
Signed-off-by: Jason Wessel <jason.wessel@...driver.com>
---
drivers/char/tty_io.c | 96 +++++++++++++++++++++++++++++++++++++++++---
drivers/serial/kgdboc.c | 26 ++++++++----
include/linux/tty_driver.h | 5 ++
3 files changed, 113 insertions(+), 14 deletions(-)
diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index fa44e6b..fe500ec 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -143,6 +143,8 @@ ssize_t redirected_tty_write(struct file *, const char __user *,
static unsigned int tty_poll(struct file *, poll_table *);
static int tty_open(struct inode *, struct file *);
static int tty_release(struct inode *, struct file *);
+static struct tty_struct *tty_driver_lookup_tty(struct tty_driver *driver,
+ struct inode *inode, int idx);
long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
#ifdef CONFIG_COMPAT
static long tty_compat_ioctl(struct file *file, unsigned int cmd,
@@ -280,6 +282,83 @@ static struct tty_driver *get_tty_driver(dev_t device, int *index)
}
#ifdef CONFIG_CONSOLE_POLL
+/**
+ * tty_console_poll_open - allocate a tty for a polled device
+ * @driver: the tty driver
+ * @filp: file pointer to point to the tty
+ * @tty_line: the minor device number
+ *
+ * This routine returns allocates an empty struct file structure
+ * to allow a polling device to open a tty. This ultimately
+ * allows the low level startup code for the uart to only be
+ * called one time, for either the polling device init or user
+ * space tty init.
+ */
+int tty_console_poll_open(struct tty_driver *driver, struct file **filp,
+ int tty_line)
+{
+ int ret = -EIO;
+ struct tty_struct *tty;
+ int inc_tty = 1;
+
+ if (!*filp)
+ *filp = get_empty_filp();
+ if (!*filp)
+ goto out;
+
+ mutex_lock(&tty_mutex);
+ if (!kernel_locked()) {
+ lock_kernel();
+ tty = tty_driver_lookup_tty(driver, NULL, tty_line);
+ if (!tty) {
+ tty = tty_init_dev(driver, tty_line, 0);
+ inc_tty = 0;
+ }
+ (*filp)->private_data = tty;
+ ret = tty->ops->open(tty, *filp);
+ unlock_kernel();
+ } else {
+ tty = tty_driver_lookup_tty(driver, NULL, tty_line);
+ if (!tty) {
+ tty = tty_init_dev(driver, tty_line, 0);
+ inc_tty = 0;
+ }
+ (*filp)->private_data = tty;
+ ret = tty->ops->open(tty, *filp);
+ }
+ if (ret == 0) {
+ file_move(*filp, &tty->tty_files);
+ tty->count += inc_tty;
+ } else {
+ put_filp(*filp);
+ *filp = NULL;
+ }
+ mutex_unlock(&tty_mutex);
+out:
+ return ret;
+}
+EXPORT_SYMBOL_GPL(tty_console_poll_open);
+
+/**
+ * tty_console_poll_close - shutdown a tty for a polled device
+ * @filp: file pointer to point to the tty
+ *
+ * Deallocate the tty device used by the polling driver, and free
+ * the associated filp.
+ */
+void tty_console_poll_close(struct file **filp)
+{
+ if (!kernel_locked()) {
+ lock_kernel();
+ tty_release_dev(*filp);
+ unlock_kernel();
+ } else {
+ tty_release_dev(*filp);
+ }
+ put_filp(*filp);
+ *filp = NULL;
+}
+EXPORT_SYMBOL_GPL(tty_console_poll_close);
/**
* tty_find_polling_driver - find device of a polled tty
@@ -552,6 +631,8 @@ static void do_tty_hangup(struct work_struct *work)
file_list_lock();
/* This breaks for file handles being sent over AF_UNIX sockets ? */
list_for_each_entry(filp, &tty->tty_files, f_u.fu_list) {
+ if (!filp->f_op)
+ continue;
if (filp->f_op->write == redirected_tty_write)
cons_filp = filp;
if (filp->f_op->write != tty_write)
@@ -1524,12 +1605,14 @@ void tty_release_dev(struct file *filp)
int devpts;
int idx;
char buf[64];
- struct inode *inode;
+ struct inode *inode = NULL;
- inode = filp->f_path.dentry->d_inode;
tty = (struct tty_struct *)filp->private_data;
- if (tty_paranoia_check(tty, inode, "tty_release_dev"))
- return;
+ if (filp->f_path.dentry) {
+ inode = filp->f_path.dentry->d_inode;
+ if (tty_paranoia_check(tty, inode, "tty_release_dev"))
+ return;
+ }
check_tty_count(tty, "tty_release_dev");
@@ -1723,7 +1806,7 @@ void tty_release_dev(struct file *filp)
release_tty(tty, idx);
/* Make this pty number available for reallocation */
- if (devpts)
+ if (devpts && inode)
devpts_kill_index(inode, idx);
}
@@ -1950,7 +2033,8 @@ static int tty_fasync(int fd, struct file *filp, int on)
lock_kernel();
tty = (struct tty_struct *)filp->private_data;
- if (tty_paranoia_check(tty, filp->f_path.dentry->d_inode, "tty_fasync"))
+ if (filp->f_path.dentry &&
+ tty_paranoia_check(tty, filp->f_path.dentry->d_inode, "tty_fasync"))
goto out;
retval = fasync_helper(fd, filp, on, &tty->fasync);
diff --git a/drivers/serial/kgdboc.c b/drivers/serial/kgdboc.c
index d5d35c3..b274a36 100644
--- a/drivers/serial/kgdboc.c
+++ b/drivers/serial/kgdboc.c
@@ -31,6 +31,7 @@ static struct kparam_string kps = {
static struct tty_driver *kgdb_tty_driver;
static int kgdb_tty_line;
+static struct file *kgdb_filp;
static int kgdboc_option_setup(char *opt)
{
@@ -73,6 +74,16 @@ static int kgdboc_rx_callback(u8 c)
__setup("kgdboc=", kgdboc_option_setup);
+static void release_kgdboc_tty(void)
+{
+ if (kgdb_tty_driver)
+ kgdb_tty_driver->ops->poll_init(kgdb_tty_driver, kgdb_tty_line,
+ NULL, (void *)-1);
+ if (kgdb_filp)
+ tty_console_poll_close(&kgdb_filp);
+ kgdb_tty_driver = NULL;
+}
+
static int configure_kgdboc(void)
{
struct tty_driver *p;
@@ -86,10 +97,7 @@ static int configure_kgdboc(void)
err = -ENODEV;
/* If a driver was previously configured remove it now */
- if (kgdb_tty_driver)
- kgdb_tty_driver->ops->poll_init(kgdb_tty_driver, kgdb_tty_line,
- NULL, (void *)-1);
- kgdb_tty_driver = NULL;
+ release_kgdboc_tty();
p = tty_find_polling_driver(config, &tty_line);
if (!p)
@@ -118,6 +126,11 @@ static int configure_kgdboc(void)
if (p->ops->poll_init(p, tty_line, str, kgdboc_rx_callback))
goto noconfig;
+ /* Open the port and obtain a tty which call low level driver startup */
+ if (tty_console_poll_open(kgdb_tty_driver, &kgdb_filp,
+ kgdb_tty_line) != 0)
+ goto noconfig;
+
err = kgdb_register_io_module(&kgdboc_io_ops);
if (err)
goto noconfig;
@@ -127,10 +140,7 @@ static int configure_kgdboc(void)
return 0;
noconfig:
- if (kgdb_tty_driver)
- kgdb_tty_driver->ops->poll_init(kgdb_tty_driver, kgdb_tty_line,
- NULL, (void *)-1);
- kgdb_tty_driver = NULL;
+ release_kgdboc_tty();
config[0] = 0;
configured = 0;
diff --git a/include/linux/tty_driver.h b/include/linux/tty_driver.h
index 4c30f16..1af8393 100644
--- a/include/linux/tty_driver.h
+++ b/include/linux/tty_driver.h
@@ -310,7 +310,12 @@ extern struct tty_driver *alloc_tty_driver(int lines);
extern void put_tty_driver(struct tty_driver *driver);
extern void tty_set_operations(struct tty_driver *driver,
const struct tty_operations *op);
+#ifdef CONFIG_CONSOLE_POLL
extern struct tty_driver *tty_find_polling_driver(char *name, int *line);
+extern int tty_console_poll_open(struct tty_driver *driver,
+ struct file **filp, int line);
+extern void tty_console_poll_close(struct file **filp);
+#endif
extern void tty_driver_kref_put(struct tty_driver *driver);
extern inline struct tty_driver *tty_driver_kref_get(struct tty_driver *d)
--
1.6.0.2
--
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