> I mean to create a char driver which contains ioctl interface to control GPIOs connected to SIM card VCC and RESET. We have a GPIO layer and existing GPIO interface support so the gpio side if they are kept independent ought to be easy. However I wonder if the separate gpio control will make the userspace side harder ? > Thirdly, I want to use usual tty function (read / write) to implement the ATR / send or receive command / PPS. > That means tty usual driver read or write will be called by user space application such as openct or else to realize the ATR and PPS. > Openct may also call above char driver to realize the power or reset function. That may be difficult to get right because of the tty object lifetime and the locking rules. One way would be to make ISO7816 a line discipline (the layer which sits about the tty). Your user space interface would then be int ldisc = N_ISO7816; ioctl(tty_fd, TIOCSETD, &ldisc); at which point the read/write/ioctl etc calls on your tty will also be routed via your ldisc so you can manage them and provide ISO7816 sensible interfaces. You'd still need a way for the ldisc to ask the tty device to manage the GPIO lines but I don't think that is too tricky to add. That way it would at least keep everything in one place and avoid adding new strange paths calling into the tty layer code via non tty devices. Take a look at the gsmld_ parts of drivers/tty/n_gsm.c for a fairly full example of a line discipline. You can ignore most of the rest of the code there, the rest is implementing GSM mux and virtual ttys. The two thing s it doesn't use are tty_set_termios(tty, &whatever) which is a helper for the ldisc or similar to set the terminal state itself. and tty->driver->ops->tiocmget/tiocmset/etc for doing things like modem lines. One way to handle the gpios transparently might be to map them to the nearest equivalent 'modem' line when in ISO7816 mode. The tty also sees the ldisc change via tty->ops->set_ldisc(). This is used by some drivers already for things like automatically selecting IRDA FIR mode when in IRDA modes. In your case the driver would set/exit ISO7816 mode when it saw this. Alan -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
