[v2,8/9] serdev: add a tty port controller driver

Message ID 20170116225436.17505-9-robh@kernel.org
State New
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Series
  • Serial slave device bus
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Commit Message

Rob Herring Jan. 16, 2017, 10:54 p.m.
Add a serdev controller driver for tty ports.

The controller is registered with serdev when tty ports are registered
with the TTY core. As the TTY core is built-in only, this has the side
effect of making serdev built-in as well.

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

Reviewed-By: Sebastian Reichel <sre@kernel.org>

---
v2:
- Sort includes
- Made goto labels more descriptive
- Use tty-> instead of serdev->tty-> where possible
- Drop DT specific check in serdev_tty_port_register. DT specifics are only
  in core bus code now.
- Comments on #endif's
- Use "depends on SERIAL_DEV_BUS != m" instead of "= y"
- Dropped module properties (not a module)

 drivers/tty/serdev/Kconfig          |   8 ++
 drivers/tty/serdev/Makefile         |   2 +
 drivers/tty/serdev/serdev-ttyport.c | 240 ++++++++++++++++++++++++++++++++++++
 include/linux/serdev.h              |  21 ++++
 4 files changed, 271 insertions(+)
 create mode 100644 drivers/tty/serdev/serdev-ttyport.c

--
2.10.1

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Comments

Rob Herring Jan. 18, 2017, 3:03 p.m. | #1
On Wed, Jan 18, 2017 at 6:42 AM, Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:
> On Mon, 2017-01-16 at 16:54 -0600, Rob Herring wrote:

>> Add a serdev controller driver for tty ports.

>>

>> The controller is registered with serdev when tty ports are registered

>> with the TTY core. As the TTY core is built-in only, this has the side

>> effect of making serdev built-in as well.

>>

>

>>

>> +if SERIAL_DEV_BUS

>> +

>> +config SERIAL_DEV_CTRL_TTYPORT

>> +     bool "Serial device TTY port controller"

>> +     depends on TTY

>

>

>> +     depends on SERIAL_DEV_BUS != m

>

> Since you have this line the

>  if SERIAL_DEV_BUS

> is redundant for it.


It is not. It is the standard pattern of

menuconfig BLAH

if BLAH
...
endif
<EOF>

If I remove the "if", then SERIAL_DEV_CTRL_TTYPORT can be enabled when
SERIAL_DEV_BUS=n which breaks the build


> So, leave either one or another (as an example you can look at

> DMADEVICES).

>

>> +

>> +#define SERPORT_BUSY 1

>> +#define SERPORT_ACTIVE       2

>> +#define SERPORT_DEAD 3

>> +

>> +struct serport {

>> +     struct tty_port *port;

>> +     struct tty_struct *tty;

>

>> +     struct tty_driver *tty_drv;

>> +     int tty_idx;

>

> Do you need tty_ prefix for them?


It's just to be clear it's the tty driver and index rather than this
driver's driver or index.


>> +static int ttyport_open(struct serdev_controller *ctrl)

>> +{

>> +     struct serport *serport =

>> serdev_controller_get_drvdata(ctrl);

>> +     struct tty_struct *tty;

>> +     struct ktermios ktermios;

>> +

>> +     tty = tty_init_dev(serport->tty_drv, serport->tty_idx);

>> +     serport->tty = tty;

>> +

>> +     serport->port->client_ops = &client_ops;

>> +     serport->port->client_data = ctrl;

>> +

>>

>

>> +     tty->receive_room = 65536;

>

> Magic?


Probably. It's just what every ldisc uses. I suppose we could need
clients to set this, but we can add that as needed.

>> +     if (tty->ops->open)

>> +             tty->ops->open(serport->tty, NULL);

>> +     else

>> +             tty_port_open(serport->port, tty, NULL);

>> +

>> +     /* Bring the UART into a known 8 bits no parity hw fc state

>> */

>> +     ktermios = tty->termios;

>> +     ktermios.c_iflag &= ~(IGNBRK | BRKINT | PARMRK | ISTRIP |

>> +                           INLCR | IGNCR | ICRNL | IXON);

>> +     ktermios.c_oflag &= ~OPOST;

>> +     ktermios.c_lflag &= ~(ECHO | ECHONL | ICANON | ISIG |

>> IEXTEN);

>> +     ktermios.c_cflag &= ~(CSIZE | PARENB);

>> +     ktermios.c_cflag |= CS8;

>> +     ktermios.c_cflag |= CRTSCTS;

>> +     tty_set_termios(tty, &ktermios);

>> +

>> +     set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);

>> +

>>

>

>> +     mutex_lock(&serport->lock);

>> +     set_bit(SERPORT_ACTIVE, &serport->flags);

>> +     mutex_unlock(&serport->lock);

>

> So, some clarification would be good to have to understand why you need

> mutex _and_ atomic operation together.

>

> What does mutex protect?


Paranoia. Actually, looking at this closer, we can get rid of the
mutex altogether.


>> +void serdev_tty_port_unregister(struct tty_port *port)

>> +{

>> +     struct serdev_controller *ctrl = port->client_data;

>> +     struct serport *serport =

>> serdev_controller_get_drvdata(ctrl);

>> +

>

>> +     if (!serport)

>> +             return;

>

> What this check prevents from?


Didn't you ask this last time? See patch #9. tty_port_destructor()
calls this unconditionally as it doesn't know whether there's a serdev
or not. ctrl may be NULL, and then serport may be NULL.

Rob
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Patch hide | download patch | download mbox

diff --git a/drivers/tty/serdev/Kconfig b/drivers/tty/serdev/Kconfig
index 3b6ecd187bef..cdc6b820cf93 100644
--- a/drivers/tty/serdev/Kconfig
+++ b/drivers/tty/serdev/Kconfig
@@ -6,3 +6,11 @@  menuconfig SERIAL_DEV_BUS
 	help
 	  Core support for devices connected via a serial port.

+if SERIAL_DEV_BUS
+
+config SERIAL_DEV_CTRL_TTYPORT
+	bool "Serial device TTY port controller"
+	depends on TTY
+	depends on SERIAL_DEV_BUS != m
+
+endif
diff --git a/drivers/tty/serdev/Makefile b/drivers/tty/serdev/Makefile
index 01a9b62183f4..0cbdb9444d9d 100644
--- a/drivers/tty/serdev/Makefile
+++ b/drivers/tty/serdev/Makefile
@@ -1,3 +1,5 @@ 
 serdev-objs := core.o

 obj-$(CONFIG_SERIAL_DEV_BUS) += serdev.o
+
+obj-$(CONFIG_SERIAL_DEV_CTRL_TTYPORT) += serdev-ttyport.o
diff --git a/drivers/tty/serdev/serdev-ttyport.c b/drivers/tty/serdev/serdev-ttyport.c
new file mode 100644
index 000000000000..bdd2db7db273
--- /dev/null
+++ b/drivers/tty/serdev/serdev-ttyport.c
@@ -0,0 +1,240 @@ 
+/*
+ * Copyright (C) 2016 Linaro Ltd., Rob Herring <robh@kernel.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+#include <linux/kernel.h>
+#include <linux/serdev.h>
+#include <linux/tty.h>
+#include <linux/tty_driver.h>
+
+#define SERPORT_BUSY	1
+#define SERPORT_ACTIVE	2
+#define SERPORT_DEAD	3
+
+struct serport {
+	struct tty_port *port;
+	struct tty_struct *tty;
+	struct tty_driver *tty_drv;
+	int tty_idx;
+	struct mutex lock;
+	unsigned long flags;
+};
+
+/*
+ * Callback functions from the tty port.
+ */
+
+static int ttyport_receive_buf(struct tty_port *port, const unsigned char *cp,
+				const unsigned char *fp, size_t count)
+{
+	struct serdev_controller *ctrl = port->client_data;
+	struct serport *serport = serdev_controller_get_drvdata(ctrl);
+
+	mutex_lock(&serport->lock);
+
+	if (!test_bit(SERPORT_ACTIVE, &serport->flags))
+		goto out_unlock;
+
+	serdev_controller_receive_buf(ctrl, cp, count);
+
+out_unlock:
+	mutex_unlock(&serport->lock);
+	return count;
+}
+
+static void ttyport_write_wakeup(struct tty_port *port)
+{
+	struct serdev_controller *ctrl = port->client_data;
+	struct serport *serport = serdev_controller_get_drvdata(ctrl);
+
+	clear_bit(TTY_DO_WRITE_WAKEUP, &port->tty->flags);
+
+	if (test_bit(SERPORT_ACTIVE, &serport->flags))
+		serdev_controller_write_wakeup(ctrl);
+}
+
+static const struct tty_port_client_operations client_ops = {
+	.receive_buf = ttyport_receive_buf,
+	.write_wakeup = ttyport_write_wakeup,
+};
+
+/*
+ * Callback functions from the serdev core.
+ */
+
+static int ttyport_write_buf(struct serdev_controller *ctrl, const unsigned char *data, size_t len)
+{
+	struct serport *serport = serdev_controller_get_drvdata(ctrl);
+	struct tty_struct *tty = serport->tty;
+
+	set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
+	return tty->ops->write(serport->tty, data, len);
+}
+
+static void ttyport_write_flush(struct serdev_controller *ctrl)
+{
+	struct serport *serport = serdev_controller_get_drvdata(ctrl);
+	struct tty_struct *tty = serport->tty;
+
+	tty_driver_flush_buffer(tty);
+}
+
+static int ttyport_write_room(struct serdev_controller *ctrl)
+{
+	struct serport *serport = serdev_controller_get_drvdata(ctrl);
+	struct tty_struct *tty = serport->tty;
+
+	return tty_write_room(tty);
+}
+
+
+static int ttyport_open(struct serdev_controller *ctrl)
+{
+	struct serport *serport = serdev_controller_get_drvdata(ctrl);
+	struct tty_struct *tty;
+	struct ktermios ktermios;
+
+	tty = tty_init_dev(serport->tty_drv, serport->tty_idx);
+	serport->tty = tty;
+
+	serport->port->client_ops = &client_ops;
+	serport->port->client_data = ctrl;
+
+	tty->receive_room = 65536;
+
+	if (tty->ops->open)
+		tty->ops->open(serport->tty, NULL);
+	else
+		tty_port_open(serport->port, tty, NULL);
+
+	/* Bring the UART into a known 8 bits no parity hw fc state */
+	ktermios = tty->termios;
+	ktermios.c_iflag &= ~(IGNBRK | BRKINT | PARMRK | ISTRIP |
+			      INLCR | IGNCR | ICRNL | IXON);
+	ktermios.c_oflag &= ~OPOST;
+	ktermios.c_lflag &= ~(ECHO | ECHONL | ICANON | ISIG | IEXTEN);
+	ktermios.c_cflag &= ~(CSIZE | PARENB);
+	ktermios.c_cflag |= CS8;
+	ktermios.c_cflag |= CRTSCTS;
+	tty_set_termios(tty, &ktermios);
+
+	set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
+
+	mutex_lock(&serport->lock);
+	set_bit(SERPORT_ACTIVE, &serport->flags);
+	mutex_unlock(&serport->lock);
+
+	tty_unlock(serport->tty);
+	return 0;
+}
+
+static void ttyport_close(struct serdev_controller *ctrl)
+{
+	struct serport *serport = serdev_controller_get_drvdata(ctrl);
+	struct tty_struct *tty = serport->tty;
+
+	mutex_lock(&serport->lock);
+
+	if (tty->ops->close)
+		tty->ops->close(tty, NULL);
+
+	tty_release_struct(tty, serport->tty_idx);
+
+	clear_bit(SERPORT_ACTIVE, &serport->flags);
+	mutex_unlock(&serport->lock);
+}
+
+static unsigned int ttyport_set_baudrate(struct serdev_controller *ctrl, unsigned int speed)
+{
+	struct serport *serport = serdev_controller_get_drvdata(ctrl);
+	struct tty_struct *tty = serport->tty;
+	struct ktermios ktermios = tty->termios;
+
+	ktermios.c_cflag &= ~CBAUD;
+	tty_termios_encode_baud_rate(&ktermios, speed, speed);
+
+	/* tty_set_termios() return not checked as it is always 0 */
+	tty_set_termios(tty, &ktermios);
+	return speed;
+}
+
+static void ttyport_set_flow_control(struct serdev_controller *ctrl, bool enable)
+{
+	struct serport *serport = serdev_controller_get_drvdata(ctrl);
+	struct tty_struct *tty = serport->tty;
+	struct ktermios ktermios = tty->termios;
+
+	if (enable)
+		ktermios.c_cflag |= CRTSCTS;
+	else
+		ktermios.c_cflag &= ~CRTSCTS;
+
+	tty_set_termios(tty, &ktermios);
+}
+
+struct serdev_controller_ops ctrl_ops = {
+	.write_buf = ttyport_write_buf,
+	.write_flush = ttyport_write_flush,
+	.write_room = ttyport_write_room,
+	.open = ttyport_open,
+	.close = ttyport_close,
+	.set_flow_control = ttyport_set_flow_control,
+	.set_baudrate = ttyport_set_baudrate,
+};
+
+struct device *serdev_tty_port_register(struct tty_port *port,
+					struct device *parent,
+					struct tty_driver *drv, int idx)
+{
+	struct serdev_controller *ctrl;
+	struct serport *serport;
+	int ret;
+
+	if (!port || !drv || !parent)
+		return ERR_PTR(-ENODEV);
+
+	ctrl = serdev_controller_alloc(parent, sizeof(struct serport));
+	if (!ctrl)
+		return ERR_PTR(-ENOMEM);
+	serport = serdev_controller_get_drvdata(ctrl);
+
+	mutex_init(&serport->lock);
+	serport->port = port;
+	serport->tty_idx = idx;
+	serport->tty_drv = drv;
+
+	ctrl->ops = &ctrl_ops;
+
+	ret = serdev_controller_add(ctrl);
+	if (ret)
+		goto err_controller_put;
+
+	dev_info(&ctrl->dev, "tty port %s%d registered\n", drv->name, idx);
+	return &ctrl->dev;
+
+err_controller_put:
+	serdev_controller_put(ctrl);
+	return ERR_PTR(ret);
+}
+
+void serdev_tty_port_unregister(struct tty_port *port)
+{
+	struct serdev_controller *ctrl = port->client_data;
+	struct serport *serport = serdev_controller_get_drvdata(ctrl);
+
+	if (!serport)
+		return;
+
+	serdev_controller_remove(ctrl);
+	port->client_ops = NULL;
+	port->client_data = NULL;
+	serdev_controller_put(ctrl);
+}
diff --git a/include/linux/serdev.h b/include/linux/serdev.h
index 6e8cd6ad0a85..fe7becd881aa 100644
--- a/include/linux/serdev.h
+++ b/include/linux/serdev.h
@@ -210,4 +210,25 @@  static inline int serdev_controller_receive_buf(struct serdev_controller *ctrl,
 	return serdev->ops->receive_buf(ctrl->serdev, data, count);
 }

+/*
+ * serdev hooks into TTY core
+ */
+struct tty_port;
+struct tty_driver;
+
+#ifdef CONFIG_SERIAL_DEV_CTRL_TTYPORT
+struct device *serdev_tty_port_register(struct tty_port *port,
+					struct device *parent,
+					struct tty_driver *drv, int idx);
+void serdev_tty_port_unregister(struct tty_port *port);
+#else
+static inline struct device *serdev_tty_port_register(struct tty_port *port,
+					   struct device *parent,
+					   struct tty_driver *drv, int idx)
+{
+	return ERR_PTR(-ENODEV);
+}
+static inline void serdev_tty_port_unregister(struct tty_port *port) {}
+#endif /* CONFIG_SERIAL_DEV_CTRL_TTYPORT */
+
 #endif /*_LINUX_SERDEV_H */