tty: uartclk value from serial_core exposed to sysfs

Added file /sys/devices/.../tty/ttySX/uartclk to allow reading
uartclk value in struct uart_port in serial_core via sysfs.

tty_register_device() has been generalized and refactored in order
to add support for setting drvdata and attribute_group to the device.

Signed-off-by: Tomas Hlavacek <tmshlvck@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

4 files changed, 104 insertions, 12 deletions

diff --git a/Documentation/ABI/testing/sysfs-tty b/Documentation/ABI/testing/sysfs-tty
index b138b663bf54..0c430150d929 100644
--- a/Documentation/ABI/testing/sysfs-tty
+++ b/Documentation/ABI/testing/sysfs-tty
@@ -17,3 +17,12 @@ Description:
                  device, like 'tty1'.
                  The file supports poll() to detect virtual
                  console switches.
+
+What:           /sys/class/tty/ttyS0/uartclk
+Date:           Sep 2012
+Contact:        Tomas Hlavacek <tmshlvck@gmail.com>
+Description:
+                 Shows the current uartclk value associated with the
+                 UART port in serial_core, that is bound to TTY like ttyS0.
+                 uartclk = 16 * baud_base
+
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 19993d89db37..f629bdf2a8cf 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -2309,6 +2309,36 @@ struct tty_driver *uart_console_device(struct console *co, int *index)
         return p->tty_driver;
 }
 
+static ssize_t uart_get_attr_uartclk(struct device *dev,
+        struct device_attribute *attr, char *buf)
+{
+        int ret;
+
+        struct tty_port *port = dev_get_drvdata(dev);
+        struct uart_state *state = container_of(port, struct uart_state, port);
+        mutex_lock(&state->port.mutex);
+        ret = snprintf(buf, PAGE_SIZE, "%d\n", state->uart_port->uartclk);
+        mutex_unlock(&state->port.mutex);
+
+        return ret;
+}
+
+static DEVICE_ATTR(uartclk, S_IRUSR | S_IRGRP, uart_get_attr_uartclk, NULL);
+
+static struct attribute *tty_dev_attrs[] = {
+        &dev_attr_uartclk.attr,
+        NULL,
+        };
+
+static struct attribute_group tty_dev_attr_group = {
+        .attrs = tty_dev_attrs,
+        };
+
+static const struct attribute_group *tty_dev_attr_groups[] = {
+        &tty_dev_attr_group,
+        NULL
+        };
+
 /**
  *      uart_add_one_port - attach a driver-defined port structure
  *      @drv: pointer to the uart low level driver structure for this port
@@ -2362,8 +2392,8 @@ int uart_add_one_port(struct uart_driver *drv, struct uart_port *uport)
          * Register the port whether it's detected or not.  This allows
          * setserial to be used to alter this ports parameters.
          */
-        tty_dev = tty_port_register_device(port, drv->tty_driver, uport->line,
-                        uport->dev);
+        tty_dev = tty_register_device_attr(drv->tty_driver, uport->line,
+                        uport->dev, port, tty_dev_attr_groups);
         if (likely(!IS_ERR(tty_dev))) {
                 device_set_wakeup_capable(tty_dev, 1);
         } else {
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index d3bf91a29303..dcb30d55d39c 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -3041,9 +3041,39 @@ static int tty_cdev_add(struct tty_driver *driver, dev_t dev,
 struct device *tty_register_device(struct tty_driver *driver, unsigned index,
                                    struct device *device)
 {
-        struct device *ret;
+        return tty_register_device_attr(driver, index, device, NULL, NULL);
+}
+EXPORT_SYMBOL(tty_register_device);
+
+/**
+ *      tty_register_device_attr - register a tty device
+ *      @driver: the tty driver that describes the tty device
+ *      @index: the index in the tty driver for this tty device
+ *      @device: a struct device that is associated with this tty device.
+ *              This field is optional, if there is no known struct device
+ *              for this tty device it can be set to NULL safely.
+ *      @drvdata: Driver data to be set to device.
+ *      @attr_grp: Attribute group to be set on device.
+ *
+ *      Returns a pointer to the struct device for this tty device
+ *      (or ERR_PTR(-EFOO) on error).
+ *
+ *      This call is required to be made to register an individual tty device
+ *      if the tty driver's flags have the TTY_DRIVER_DYNAMIC_DEV bit set.  If
+ *      that bit is not set, this function should not be called by a tty
+ *      driver.
+ *
+ *      Locking: ??
+ */
+struct device *tty_register_device_attr(struct tty_driver *driver,
+                                   unsigned index, struct device *device,
+                                   void *drvdata,
+                                   const struct attribute_group **attr_grp)
+{
         char name[64];
-        dev_t dev = MKDEV(driver->major, driver->minor_start) + index;
+        dev_t devt = MKDEV(driver->major, driver->minor_start) + index;
+        struct device *dev = NULL;
+        int retval = -ENODEV;
         bool cdev = false;
 
         if (index >= driver->num) {
@@ -3058,19 +3088,38 @@ struct device *tty_register_device(struct tty_driver *driver, unsigned index,
                 tty_line_name(driver, index, name);
 
         if (!(driver->flags & TTY_DRIVER_DYNAMIC_ALLOC)) {
-                int error = tty_cdev_add(driver, dev, index, 1);
-                if (error)
-                        return ERR_PTR(error);
+                retval = tty_cdev_add(driver, devt, index, 1);
+                if (retval)
+                        goto error;
                 cdev = true;
         }
 
-        ret = device_create(tty_class, device, dev, NULL, name);
-        if (IS_ERR(ret) && cdev)
-                cdev_del(&driver->cdevs[index]);
+        dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+        if (!dev) {
+                retval = -ENOMEM;
+                goto error;
+        }
 
-        return ret;
+        dev->devt = devt;
+        dev->class = tty_class;
+        dev->parent = device;
+        dev_set_name(dev, "%s", name);
+        dev->groups = attr_grp;
+        dev_set_drvdata(dev, drvdata);
+
+        retval = device_register(dev);
+        if (retval)
+                goto error;
+
+        return dev;
+
+error:
+        put_device(dev);
+        if (cdev)
+                cdev_del(&driver->cdevs[index]);
+        return ERR_PTR(retval);
 }
-EXPORT_SYMBOL(tty_register_device);
+EXPORT_SYMBOL_GPL(tty_register_device_attr);
 
 /**
  *      tty_unregister_device - unregister a tty device
diff --git a/include/linux/tty.h b/include/linux/tty.h
index 9892121354cd..599d60347bf0 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -412,6 +412,10 @@ extern int tty_register_driver(struct tty_driver *driver);
 extern int tty_unregister_driver(struct tty_driver *driver);
 extern struct device *tty_register_device(struct tty_driver *driver,
                                           unsigned index, struct device *dev);
+extern struct device *tty_register_device_attr(struct tty_driver *driver,
+                                unsigned index, struct device *device,
+                                void *drvdata,
+                                const struct attribute_group **attr_grp);
 extern void tty_unregister_device(struct tty_driver *driver, unsigned index);
 extern int tty_read_raw_data(struct tty_struct *tty, unsigned char *bufp,
                              int buflen);