[PATCH 5/9] tty_port: Add port client functions

Rob Herring
2017-01-06T16:26:31Z

Introduce a client (upward direction) operations struct for tty_port
clients. Initially supported operations are for receiving data and write
wake-up. This will allow for having clients other than an ldisc.

Convert the calls to the ldisc to use the client ops as the default
operations.

Signed-off-by: Rob Herring <robh@kernel.org>
---

The major change here is the access of the tty ptr and the reference taken
on the ldisc are moved into the client_ops rx function for the the ldisc.
I *think* this should be okay, but no doubt I don't understand all the
intricacies of the locking here. It does make the implementation a bit
cleaner in that the tty buffer handling is free from struct tty and the
ldisc.

drivers/tty/tty_buffer.c | 17 +++--------------
drivers/tty/tty_port.c | 39 ++++++++++++++++++++++++++++++++++++++-
include/linux/tty.h | 9 ++++++++-
3 files changed, 49 insertions(+), 16 deletions(-)

diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c
index f4dc3e296dd5..4e7a4e9dcf4d 100644
--- a/drivers/tty/tty_buffer.c
+++ b/drivers/tty/tty_buffer.c
@@ -437,7 +437,7 @@ int tty_ldisc_receive_buf(struct tty_ldisc *ld, const unsigned char *p,
EXPORT_SYMBOL_GPL(tty_ldisc_receive_buf);

static int
-receive_buf(struct tty_ldisc *ld, struct tty_buffer *head, int count)
+receive_buf(struct tty_port *port, struct tty_buffer *head, int count)
{
unsigned char *p = char_buf_ptr(head, head->read);
char *f = NULL;
@@ -445,7 +445,7 @@ receive_buf(struct tty_ldisc *ld, struct tty_buffer *head, int count)
if (~head->flags & TTYB_NORMAL)
f = flag_buf_ptr(head, head->read);

- return tty_ldisc_receive_buf(ld, p, f, count);
+ return port->client_ops->receive_buf(port, p, f, count);
}

/**
@@ -465,16 +465,6 @@ static void flush_to_ldisc(struct work_struct *work)
{
struct tty_port *port = container_of(work, struct tty_port, buf.work);
struct tty_bufhead *buf = &port->buf;
- struct tty_struct *tty;
- struct tty_ldisc *disc;
-
- tty = READ_ONCE(port->itty);
- if (tty == NULL)
- return;
-
- disc = tty_ldisc_ref(tty);
- if (disc == NULL)
- return;

mutex_lock(&buf->lock);

@@ -504,7 +494,7 @@ static void flush_to_ldisc(struct work_struct *work)
continue;
}

- count = receive_buf(disc, head, count);
+ count = receive_buf(port, head, count);
if (!count)
break;
head->read += count;
@@ -512,7 +502,6 @@ static void flush_to_ldisc(struct work_struct *work)

mutex_unlock(&buf->lock);

- tty_ldisc_deref(disc);
}

/**
diff --git a/drivers/tty/tty_port.c b/drivers/tty/tty_port.c
index 1d8804843103..232a8cbf47bc 100644
--- a/drivers/tty/tty_port.c
+++ b/drivers/tty/tty_port.c
@@ -17,6 +17,41 @@
#include <linux/delay.h>
#include <linux/module.h>

+static int tty_port_default_receive_buf(struct tty_port *port,
+ const unsigned char *p,
+ const unsigned char *f, size_t count)
+{
+ int ret;
+ struct tty_struct *tty;
+ struct tty_ldisc *disc;
+
+ tty = READ_ONCE(port->itty);
+ if (!tty)
+ return 0;
+
+ disc = tty_ldisc_ref(tty);
+ if (!disc)
+ return 0;
+
+ ret = tty_ldisc_receive_buf(disc, p, (char *)f, count);
+
+ tty_ldisc_deref(disc);
+
+ return ret;
+}
+
+static void tty_port_default_wakeup(struct tty_port *port)
+{
+ /* tty_port_tty_wakeup already took a reference to the tty */
+ tty_wakeup(port->tty);
+}
+
+static const struct tty_port_client_operations default_client_ops = {
+ .receive_buf = tty_port_default_receive_buf,
+ .write_wakeup = tty_port_default_wakeup,
+};
+
+
void tty_port_init(struct tty_port *port)
{
memset(port, 0, sizeof(*port));
@@ -28,6 +63,7 @@ void tty_port_init(struct tty_port *port)
spin_lock_init(&port->lock);
port->close_delay = (50 * HZ) / 100;
port->closing_wait = (3000 * HZ) / 100;
+ port->client_ops = &default_client_ops;
kref_init(&port->kref);
}
EXPORT_SYMBOL(tty_port_init);
@@ -275,7 +311,8 @@ void tty_port_tty_wakeup(struct tty_port *port)
struct tty_struct *tty = tty_port_tty_get(port);

if (tty) {
- tty_wakeup(tty);
+ if (test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags))
+ port->client_ops->write_wakeup(port);
tty_kref_put(tty);
}
}
diff --git a/include/linux/tty.h b/include/linux/tty.h
index 21c0fabfed60..1017e904c0a3 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -217,12 +217,18 @@ struct tty_port_operations {
/* Called on the final put of a port */
void (*destruct)(struct tty_port *port);
};
-
+
+struct tty_port_client_operations {
+ int (*receive_buf)(struct tty_port *port, const unsigned char *, const unsigned char *, size_t);
+ void (*write_wakeup)(struct tty_port *port);
+};
+
struct tty_port {
struct tty_bufhead buf; /* Locked internally */
struct tty_struct *tty; /* Back pointer */
struct tty_struct *itty; /* internal back ptr */
const struct tty_port_operations *ops; /* Port operations */
+ const struct tty_port_client_operations *client_ops; /* Port client operations */
spinlock_t lock; /* Lock protecting tty field */
int blocked_open; /* Waiting to open */
int count; /* Usage count */
@@ -241,6 +247,7 @@ struct tty_port {
based drain is needed else
set to size of fifo */
struct kref kref; /* Ref counter */
+ void *client_data;
};

/* tty_port::iflags bits -- use atomic bit ops */
--
2.10.1