Add a nordy sysfs attribute to suppress raising the modem-control lines on open to signal DTE readiness.
This can be use 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 <[email protected]> --- drivers/usb/serial/bus.c | 38 ++++++++++++++++++++++++++++++++++++-- 1 file changed, 36 insertions(+), 2 deletions(-) diff --git a/drivers/usb/serial/bus.c b/drivers/usb/serial/bus.c index eb0195cf37dd..37bbeab6666e 100644 --- a/drivers/usb/serial/bus.c +++ b/drivers/usb/serial/bus.c @@ -35,6 +35,40 @@ static int usb_serial_device_match(struct device *dev, return 0; } +static ssize_t nordy_show(struct device *dev, struct device_attribute *attr, + char *buf) +{ + struct usb_serial_port *port = dev_get_drvdata(dev); + + return sprintf(buf, "%d\n", tty_port_nordy(&port->port)); +} + +static ssize_t nordy_store(struct device *dev, struct device_attribute *attr, + const char *buf, size_t count) +{ + struct usb_serial_port *port = dev_get_drvdata(dev); + unsigned int val; + int ret; + + ret = kstrtouint(buf, 0, &val); + if (ret) + return ret; + + if (val > 1) + return -EINVAL; + + tty_port_set_nordy(&port->port, val); + + return count; +} +static DEVICE_ATTR_RW(nordy); + +static struct attribute *tty_attrs[] = { + &dev_attr_nordy.attr, + NULL +}; +ATTRIBUTE_GROUPS(tty); + static int usb_serial_device_probe(struct device *dev) { struct usb_serial_driver *driver; @@ -60,8 +94,8 @@ static int usb_serial_device_probe(struct device *dev) } minor = port->minor; - tty_dev = tty_port_register_device(&port->port, usb_serial_tty_driver, - minor, dev); + tty_dev = tty_port_register_device_attr(&port->port, + usb_serial_tty_driver, minor, dev, port, tty_groups); if (IS_ERR(tty_dev)) { retval = PTR_ERR(tty_dev); goto err_port_remove; -- 2.26.2
