gsm 07.10即GSM Multiplexer 及ussp源码

ussp.txt: Userspace serial ports. Introduction ------------ This driver allows serial port drivers to be written in userspace. This will probably incur a bit over overhead, but I don't expect it to be unusable. In fact, intelligent cards like "sx" already hold up characters upto 20 ms before reporting them to the OS. It must be very well possible to handle things faster than that. This driver was written to allow access to the perle RAS server products. It can easily be driven using a userspace deamon, while interfacing with the kernel internals on the network level would be harder. Technical details ----------------- The deamon opens the ussp_master device. It then uses the USSP_SET_PORT ioctl to associate the filedescriptor with a port. From that moment onward, the device is a "pipe" that transfers data between the serial port and the kernel driver. struct operation { enum op; unsigned long len; unsigned long arg; unsigned char data[]; }; Write: (kernel -> Userspace) op = USSP_WRITE; len = length of data. data[] holds the data. Read: (Userspace -> kernel) op = USSP_READ; len = length of data. data[] holds the data. set_termios: (kernel -> userspace) op = USSP_SET_TERMIOS; len = size of termios structure. (userspace can return error on unsupported sizes). data[] Termios structure. modem_signal_change: (bidirectional) /* Either side ignores the bits that are not setable */ op = USSP_MSC; len = 0; arg = the logical OR of: DCD 0x01 RI 0x02 RTS 0x04 CTS 0x08 DTR 0x10 DSR 0x20 open: (kernel -> userspace) op = USSP_OPEN; len = 0; arg = open flags; open_ok: (userspace -> kernel) op = USSP_OPEN_RESULT; len = 0l arg = result code (0 = OK, other = Errno); close: (kernel -> userspace) op = USSP_CLOSE; len = 0;