Hello list, I have a imx6ul connected to a stm32 controller via a serial interface. I need to implement a little protocol to talk towards the stm32 controller for send and receive ontop of the serial line. I found out that I have to write my own line discpline driver for doing this. After digging around in drivers/tty/n_* I have a little idea what to do here. I already attached my demo ldisc to a /dev/ttymxc7 via the ldattach command in userspace. This looks fine so far. Here my first Questions: Is there a way to permanent attach the ldisc to an serial interface in the Kernel? I have a reset GPIO to reset the stm32 controller. I would like to toggle this GPIO on opening the device. But the open() method in the ldisc driver seems the wrong place to do this. But in which open() should I do this? the underlying serial imx.c driver do not have any open() and I'am using this driver also for other serial lines? useful links to the ldisc topic: https://www.kernel.org/doc/Documentation/serial/tty.txt http://www.embeddedlinux.org.cn/essentiallinuxdevicedrivers/ Best Regards, Oliver