On Wed, Sep 19, 2018 at 07:16:12AM -1000, Steve Sakoman wrote:
> Add a "pps_4wire" file to serial ports in sysfs in case the kernel is
> configured with CONFIG_PPS_CLIENT_LDISC. Writing 1 to the file enables
> the use of CTS instead of DCD for PPS signal input. This is necessary
> in case a serial port is not completely wired.
> Though this affects PPS processing the patch is against the serial core
> as the source of the serial port PPS event dispatching has to be
> modified. Furthermore it should be possible to modify the source of
> serial port PPS event dispatching before changing the line discipline.
>
> Signed-off-by: Andreas Steinmetz <ast@xxxxxxxx>
> Signed-off-by: Steve Sakoman <steve@xxxxxxxxxxx>
> Tested-by: Steve Sakoman <steve@xxxxxxxxxxx>
> ---
> Documentation/ABI/testing/sysfs-tty | 9 +++++
> drivers/tty/serial/serial_core.c | 71 ++++++++++++++++++++++++++++++++++++-
> include/linux/serial_core.h | 3 +-
> 3 files changed, 81 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/ABI/testing/sysfs-tty b/Documentation/ABI/testing/sysfs-tty
> index 9eb3c2b..441105a 100644
> --- a/Documentation/ABI/testing/sysfs-tty
> +++ b/Documentation/ABI/testing/sysfs-tty
> @@ -154,3 +154,12 @@ Description:
> device specification. For example, when user sets 7bytes on
> 16550A, which has 1/4/8/14 bytes trigger, the RX trigger is
> automatically changed to 4 bytes.
> +
> +What: /sys/class/tty/ttyS0/pps_4wire
> +Date: September 2018
> +Contact: Steve Sakoman <steve@xxxxxxxxxxx>
> +Description:
> + Shows/sets "4 wire" mode for the PPS input to the serial driver.
> + For fully implemented serial ports PPS is normally provided
> + on the DCD line. For partial "4 wire" implementations CTS is
> + used instead of DCD.
> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
> index 80bb56f..5839bed 100644
> --- a/drivers/tty/serial/serial_core.c
> +++ b/drivers/tty/serial/serial_core.c
> @@ -2664,6 +2664,56 @@ static ssize_t uart_get_attr_iomem_reg_shift(struct device *dev,
> return snprintf(buf, PAGE_SIZE, "%d\n", tmp.iomem_reg_shift);
> }
>
> +static ssize_t uart_get_attr_pps_4wire(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct tty_port *port = dev_get_drvdata(dev);
> + struct uart_state *state = container_of(port, struct uart_state, port);
> + struct uart_port *uport;
> + int mode = 0;
> +
> + mutex_lock(&port->mutex);
> + uport = uart_port_check(state);
> + if (!uport)
> + goto out;
> +
> + mode = uport->pps_4wire;
> +
> +out:
> + mutex_unlock(&port->mutex);
> + return snprintf(buf, PAGE_SIZE, mode ? "yes" : "no");
No need to care about the size of the buffer when only dealing with a
single page. sprintf() is fine here.
> +}
> +
> +static ssize_t uart_set_attr_pps_4wire(struct device *dev,
> + struct device_attribute *attr, const char *buf, size_t count)
> +{
> + struct tty_port *port = dev_get_drvdata(dev);
> + struct uart_state *state = container_of(port, struct uart_state, port);
> + struct uart_port *uport;
> + bool mode;
> + int ret;
> +
> + if (!count)
> + return -EINVAL;
> +
> + ret = kstrtobool(buf, &mode);
> + if (ret < 0)
> + return ret;
> +
> + mutex_lock(&port->mutex);
> + uport = uart_port_check(state);
> + if (!uport)
> + goto out;
> +
> + spin_lock_irq(&uport->lock);
> + uport->pps_4wire = mode;
> + spin_unlock_irq(&uport->lock);
> +
> +out:
> + mutex_unlock(&port->mutex);
> + return count;
> +}
> +
> static DEVICE_ATTR(type, S_IRUSR | S_IRGRP, uart_get_attr_type, NULL);
> static DEVICE_ATTR(line, S_IRUSR | S_IRGRP, uart_get_attr_line, NULL);
> static DEVICE_ATTR(port, S_IRUSR | S_IRGRP, uart_get_attr_port, NULL);
> @@ -2677,6 +2727,8 @@ static DEVICE_ATTR(custom_divisor, S_IRUSR | S_IRGRP, uart_get_attr_custom_divis
> static DEVICE_ATTR(io_type, S_IRUSR | S_IRGRP, uart_get_attr_io_type, NULL);
> static DEVICE_ATTR(iomem_base, S_IRUSR | S_IRGRP, uart_get_attr_iomem_base, NULL);
> static DEVICE_ATTR(iomem_reg_shift, S_IRUSR | S_IRGRP, uart_get_attr_iomem_reg_shift, NULL);
> +static DEVICE_ATTR(pps_4wire, S_IRUSR | S_IWUSR | S_IRGRP,
> + uart_get_attr_pps_4wire, uart_set_attr_pps_4wire);
DEVICE_ATTR_RW()? All of these should get fixed up eventually as well,
but let's not add to the bad style if possible :)
Also, it's good to use the output of scripts/get_maintainer.pl to figure
out who to cc: for patch review.
thanks,
greg k-h
