On Mon, 30 Apr 2012 15:51:59 -0700 "H. Peter Anvin" <hpa@xxxxxxxxx> wrote: > On 04/30/2012 03:22 PM, NeilBrown wrote: > > > > What I would really like is to integrate it closely with the state > > of the UART. i.e. if the /dev/ttyO1 device is open, then the GPS > > is "on". If not then it is "off". Similarly if /dev/tty/O0 is > > open, bluetooth is "on", else "off". However I cannot find any way > > to "plug in" to the tty or serial drivers to perform an arbitrary > > action on first-open or last-close. Is something like that > > possible? If not, is it a reasonable thing to ask? Any suggests > > about where to put such a hook? > > > > I don't think that's the right interface. Just because the port is > currently open doesn't mean the device is active, nor vice versa. ALL > it means is that someone currently has an access handle to it. > > Since a serial port models, well, a *port*, it is logical to think of > a (hypothetical) socket containing an RS-232 connector as well as a > power outlet. Given that, it would be logical to drive the "power > connector" using the same type of interface used for the other parts > of an RS-232 control, meaning either with termios flags or via a > dedicated control ioctl (TIOCPOWER?). Actually several of our virtual tty interfaces treat open as meaning powered up. It's a fairly logical power management model. A lot of our real tty ports do the same as well and kill power on the last close. At the tty layer the tty_port helper callbacks port->activate() and port->shutdown() provide the needed functionality. You don't however want to be "hooking" this - your platform needs to provide its own versions of the relevant operations in the OMAP serial driver. 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
