Re: [PATCH v2 2/6] serial: core: add sysfs attribute to suppress ready signalling on open

Jiri Slaby
2022-06-02T07:48:24Z

On 31. 05. 22, 6:36, Mychaela N. Falconia wrote:
> From: Johan Hovold <johan@kernel.org>
>
> Add a nordy sysfs attribute to suppress raising the modem-control lines
> on open to signal DTE readiness.
>
> This can be used to prevent undesirable side-effects on open for
> applications where the DTR and RTS lines are used for non-standard
> purposes such as generating power-on and reset pulses.
>
> Signed-off-by: Johan Hovold <johan@kernel.org>
> Signed-off-by: Mychaela N. Falconia <falcon@freecalypso.org>
> ---
> Documentation/ABI/testing/sysfs-tty | 7 +++++++
> drivers/tty/serial/serial_core.c | 26 ++++++++++++++++++++++++++
> 2 files changed, 33 insertions(+)
>
> diff --git a/Documentation/ABI/testing/sysfs-tty b/Documentation/ABI/testing/sysfs-tty
> index 820e412d38a8..98cb5cf0af75 100644
> --- a/Documentation/ABI/testing/sysfs-tty
> +++ b/Documentation/ABI/testing/sysfs-tty
> @@ -161,3 +161,10 @@ Contact: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Description:
> Allows user to detach or attach back the given device as
> kernel console. It shows and accepts a boolean variable.
> +
> +What: /sys/class/tty/ttyS0/nordy

s@ttyS0@ttyS<x>@

> +Date: November 2020
> +Contact: Johan Hovold <johan@kernel.org>
> +Description:
> + Show and store the port NORDY flag which suppresses raising
> + the modem-control lines on open to signal DTE readiness.
> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
> index 9a85b41caa0a..a17ac4efaceb 100644
> --- a/drivers/tty/serial/serial_core.c
> +++ b/drivers/tty/serial/serial_core.c
> @@ -2870,6 +2870,30 @@ static ssize_t console_store(struct device *dev,
> return ret < 0 ? ret : count;
> }
>
> +static ssize_t nordy_show(struct device *dev, struct device_attribute *attr,
> + char *buf)
> +{
> + struct tty_port *port = dev_get_drvdata(dev);
> +
> + return sprintf(buf, "%d\n", tty_port_nordy(port));

sysfs_emit()? (Even if I know %d won't overflow PAGE_SIZE :P.)

thanks,
--
js
suse labs