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

[Jiri Slaby <jirislaby@kernel.org>]

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