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Subject[PATCH 04/70] tty: Introduce a tty_port common structure
Date
From: Alan Cox <alan@redhat.com>

Every tty driver has its own concept of a port structure and because they all
differ we cannot extract commonality. Begin fixing this by creating a structure
drivers can elect to use so that over time we can push fields into this and
create commonality and then introduce common methods.
Signed-off-by: Alan Cox <alan@redhat.com>
---
drivers/char/tty_io.c | 34 ++++++++++++++++++++++++++++++++++
include/linux/tty.h | 30 +++++++++++++++++++++++++++++-
2 files changed, 63 insertions(+), 1 deletions(-)

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index ab1dd0a..1856096 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -2088,6 +2088,40 @@ ssize_t redirected_tty_write(struct file *file, const char __user *buf,
return tty_write(file, buf, count, ppos);
}

+void tty_port_init(struct tty_port *port)
+{
+ memset(port, 0, sizeof(*port));
+ init_waitqueue_head(&port->open_wait);
+ init_waitqueue_head(&port->close_wait);
+ mutex_init(&port->mutex);
+}
+EXPORT_SYMBOL(tty_port_init);
+
+int tty_port_alloc_xmit_buf(struct tty_port *port)
+{
+ /* We may sleep in get_zeroed_page() */
+ mutex_lock(&port->mutex);
+ if (port->xmit_buf == NULL)
+ port->xmit_buf = (unsigned char *)get_zeroed_page(GFP_KERNEL);
+ mutex_unlock(&port->mutex);
+ if (port->xmit_buf == NULL)
+ return -ENOMEM;
+ return 0;
+}
+EXPORT_SYMBOL(tty_port_alloc_xmit_buf);
+
+void tty_port_free_xmit_buf(struct tty_port *port)
+{
+ mutex_lock(&port->mutex);
+ if (port->xmit_buf != NULL) {
+ free_page((unsigned long)port->xmit_buf);
+ port->xmit_buf = NULL;
+ }
+ mutex_unlock(&port->mutex);
+}
+EXPORT_SYMBOL(tty_port_free_xmit_buf);
+
+
static char ptychar[] = "pqrstuvwxyzabcde";

/**
diff --git a/include/linux/tty.h b/include/linux/tty.h
index 013711e..d7c695b 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -166,6 +166,29 @@ struct tty_bufhead {

struct device;
struct signal_struct;
+
+/*
+ * Port level information. Each device keeps its own port level information
+ * so provide a common structure for those ports wanting to use common support
+ * routines.
+ *
+ * The tty port has a different lifetime to the tty so must be kept apart.
+ * In addition be careful as tty -> port mappings are valid for the life
+ * of the tty object but in many cases port -> tty mappings are valid only
+ * until a hangup so don't use the wrong path.
+ */
+
+struct tty_port {
+ struct tty_struct *tty; /* Back pointer */
+ int blocked_open; /* Waiting to open */
+ int count; /* Usage count */
+ wait_queue_head_t open_wait; /* Open waiters */
+ wait_queue_head_t close_wait; /* Close waiters */
+ unsigned long flags; /* TTY flags ASY_*/
+ struct mutex mutex; /* Locking */
+ unsigned char *xmit_buf; /* Optional buffer */
+};
+
/*
* Where all of the state associated with a tty is kept while the tty
* is open. Since the termios state should be kept even if the tty
@@ -214,7 +237,7 @@ struct tty_struct {
struct list_head tty_files;

#define N_TTY_BUF_SIZE 4096
-
+
/*
* The following is data for the N_TTY line discipline. For
* historical reasons, this is included in the tty structure.
@@ -242,6 +265,7 @@ struct tty_struct {
spinlock_t read_lock;
/* If the tty has a pending do_SAK, queue it here - akpm */
struct work_struct SAK_work;
+ struct tty_port *port;
};

/* tty magic number */
@@ -350,6 +374,10 @@ extern void tty_write_unlock(struct tty_struct *tty);
extern int tty_write_lock(struct tty_struct *tty, int ndelay);
#define tty_is_writelocked(tty) (mutex_is_locked(&tty->atomic_write_lock))

+extern void tty_port_init(struct tty_port *port);
+extern int tty_port_alloc_xmit_buf(struct tty_port *port);
+extern void tty_port_free_xmit_buf(struct tty_port *port);
+


/* n_tty.c */


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