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Message-Id: <201208141450.23453.marek.vasut@gmail.com>
Date: Tue, 14 Aug 2012 14:50:23 +0200
From: Marek Vasut <marek.vasut@...il.com>
To: Tomas Hlavacek <tmshlvck@...il.com>
Cc: gregkh@...uxfoundation.org, alan@...ux.intel.com,
linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] [RFC] uartclk from serial_core exposed to sysfs
Dear Tomas Hlavacek,
> Support for read/modify of uartclk via sysfs added.
> It may prove useful with some no-name cards that
> has different oscillator speeds and no distinguishing
> PCI IDs to allow autodetection. It allows better integration
> with udev and/or init scripts.
>
> Signed-off-by: Tomas Hlavacek <tmshlvck@...il.com>
> ---
> drivers/tty/serial/serial_core.c | 54
> ++++++++++++++++++++++++++++++++++++++ drivers/tty/tty_io.c |
> 17 ++++++++++++
> include/linux/tty.h | 2 ++
> 3 files changed, 73 insertions(+)
>
> diff --git a/drivers/tty/serial/serial_core.c
> b/drivers/tty/serial/serial_core.c index a21dc8e..059b438 100644
> --- a/drivers/tty/serial/serial_core.c
> +++ b/drivers/tty/serial/serial_core.c
> @@ -2293,6 +2293,46 @@ struct tty_driver *uart_console_device(struct
> console *co, int *index) return p->tty_driver;
> }
>
> +static ssize_t get_attr_uartclk(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + int ret;
> +
> + struct uart_state *state = (struct uart_state *)(dev_get_drvdata(dev));
You don't need this cast here.
> + mutex_lock(&state->port.mutex);
> + ret = snprintf(buf, PAGE_SIZE, "%d\n", state->uart_port->uartclk);
Do you really need such a large buffer (PAGE_SIZE) ?
> + mutex_unlock(&state->port.mutex);
> + return ret;
> +}
> +
> +static ssize_t set_attr_uartclk(struct device *dev,
> + struct device_attribute *attr, const char *buf, size_t count)
> +{
> + struct uart_state *state = (struct uart_state *)(dev_get_drvdata(dev));
> + unsigned int val;
> + int ret;
> +
> + ret = kstrtouint(buf, 10, &val);
> + if (ret)
> + return ret;
> +
> + mutex_lock(&state->port.mutex);
> +
> + /*
> + * Check value: baud_base has to be more than 9600
> + * and uartclock = baud_base * 16 .
> + */
> + if (val >= 153600)
> + state->uart_port->uartclk = val;
This magic value here would use some documentation.
> + mutex_unlock(&state->port.mutex);
> +
> + return count;
> +}
> +
> +static DEVICE_ATTR(uartclk, S_IRUGO | S_IWUSR, get_attr_uartclk,
> + set_attr_uartclk);
> +
> /**
> * uart_add_one_port - attach a driver-defined port structure
> * @drv: pointer to the uart low level driver structure for this port
> @@ -2355,6 +2395,14 @@ int uart_add_one_port(struct uart_driver *drv,
> struct uart_port *uport) }
>
> /*
> + * Expose uartclk in sysfs. Use driverdata of the tty device for
> + * referencing the UART port.
> + */
> + dev_set_drvdata(tty_dev, state);
> + if (device_create_file(tty_dev, &dev_attr_uartclk) < 0)
> + dev_err(tty_dev, "Failed to add uartclk attr\n");
> +
> + /*
> * Ensure UPF_DEAD is not set.
> */
> uport->flags &= ~UPF_DEAD;
> @@ -2397,6 +2445,12 @@ int uart_remove_one_port(struct uart_driver *drv,
> struct uart_port *uport) mutex_unlock(&port->mutex);
>
> /*
> + * Remove uartclk file from sysfs.
> + */
> + device_remove_file(tty_lookup_device(drv->tty_driver, uport->line),
> + &dev_attr_uartclk);
> +
> + /*
> * Remove the devices from the tty layer
> */
> tty_unregister_device(drv->tty_driver, uport->line);
> diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
> index b425c79..8ea8622 100644
> --- a/drivers/tty/tty_io.c
> +++ b/drivers/tty/tty_io.c
> @@ -3049,6 +3049,23 @@ void tty_unregister_device(struct tty_driver
> *driver, unsigned index) }
> EXPORT_SYMBOL(tty_unregister_device);
>
> +/*
> + * tty_lookup_device - lookup a tty device
> + * @driver: the tty driver that describes the tty device
> + * @index: the index in the tty driver for this tty device
> + *
> + * This function returns a struct device pointer when device has
> + * been found and NULL otherwise.
> + *
> + * Locking: ??
> + */
> +struct device *tty_lookup_device(struct tty_driver *driver, unsigned
> index) +{
> + dev_t devt = MKDEV(driver->major, driver->minor_start) + index;
> + return class_find_device(tty_class, NULL, &devt, dev_match_devt);
> +}
> +EXPORT_SYMBOL(tty_lookup_device);
> +
> struct tty_driver *__alloc_tty_driver(int lines, struct module *owner)
> {
> struct tty_driver *driver;
> diff --git a/include/linux/tty.h b/include/linux/tty.h
> index 9f47ab5..5d408a1 100644
> --- a/include/linux/tty.h
> +++ b/include/linux/tty.h
> @@ -410,6 +410,8 @@ 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_lookup_device(struct tty_driver *driver,
> + unsigned index);
> 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);
--
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