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UCOM(9)                NetBSD Kernel Developer's Manual                UCOM(9)


NAME

     ucom -- interface for USB tty like devices


DESCRIPTION

     The ucom driver is a (relatively) easy way to make a USB device look like
     a tty(4).  It basically takes two bulk pipes, input and output, and makes
     a tty out of them.  This is useful for a number of device types, e.g.,
     serial ports (see uftdi(4)), modems (see umodem(4)), and devices that
     traditionally look like a tty (see uvisor(4)).

     Communication between the real driver and the ucom driver is via the
     attachment arguments (when attached) and via the ucom_methods struct


ATTACHMENT

     struct ucom_attach_args {
             int portno;
             int bulkin;
             int bulkout;
             u_int ibufsize;
             u_int ibufsizepad;
             u_int obufsize;
             u_int obufsizepad;
             usbd_device_handle device;
             usbd_interface_handle iface;
             struct ucom_methods *methods;
             void *arg;
     };

     int portno
             identifies the port if the devices should have more than one ucom
             attached.  Use the value UCOM_UNK_PORTNO if there is only one
             port.

     int bulkin
             the number of the bulk input pipe.

     int bulkout
             the number of the bulk output pipe.

     u_int ibufsize
             the size of the read requests on the bulk in pipe.

     u_int ibufsizepad
             the size of the input buffer.  This is usually the same as
             ibufsize.

     u_int obufsize
             the size of the write requests on the bulk out pipe.

     u_int ibufsizepad
             the size of the output buffer.  This is usually the same as
             obufsize.

     usbd_device_handle device
             a handle to the device.

     usbd_interface_handle iface
             a handle to the interface that should be used.

     struct ucom_methods *methods
             a pointer to the methods that the ucom driver should use for fur-
             ther communication with the driver.

     void *arg
             the value that should be passed as first argument to each method.


METHODS

     The ucom_methods struct contains a number of function pointers used by
     the ucom driver at various stages.  If the device is not interested in
     being called at a particular point it should just use a NULL pointer and
     the ucom driver will use a sensible default.

     struct ucom_methods {
             void (*ucom_get_status)(void *sc, int portno,
                                     u_char *lsr, u_char *msr);
             void (*ucom_set)(void *sc, int portno, int reg, int onoff);
     #define UCOM_SET_DTR 1
     #define UCOM_SET_RTS 2
     #define UCOM_SET_BREAK 3
             int (*ucom_param)(void *sc, int portno, struct termios *);
             int (*ucom_ioctl)(void *sc, int portno, u_long cmd,
                               void *data, int flag, struct lwp *l);
             int (*ucom_open)(void *sc, int portno);
             void (*ucom_close)(void *sc, int portno);
             void (*ucom_read)(void *sc, int portno, u_char **ptr,
                               uint32_t *count);
             void (*ucom_write)(void *sc, int portno, u_char *to,
                                u_char *from, uint32_t *count);
     };

     void (*ucom_get_status)(void *sc, int portno, u_char *lsr, u_char *msr)
             get the status of port portno.  The status consists of the line
             status, lsr, and the modem status msr.  The contents of these two
             bytes is exactly as for a 16550 UART.

     void (*ucom_set)(void *sc, int portno, int reg, int onoff)
             Set (or unset) a particular feature of a port.

     int (*ucom_param)(void *sc, int portno, struct termios *t)
             Set the speed, number of data bit, stop bits, and parity of a
             port according to the termios(4) struct.

     int (*ucom_ioctl)(void *sc, int portno, u_long cmd, void *data, int flag,
             struct lwp *l)
             implements any non-standard ioctl(2) that a device needs.

     int (*ucom_open)(void *sc, int portno)
             called just before the ucom driver opens the bulk pipes for the
             port.

     void (*ucom_close)(void *sc, int portno)
             called just after the ucom driver closes the bulk pipes for the
             port.

     void (*ucom_read)(void *sc, int portno, u_char **ptr, uint32_t *count)
             if the data delivered on the bulk pipe is not just the raw input
             characters this routine needs to increment ptr by as many charac-
             ters to skip from the start of the raw input and decrement count
             by as many characters to truncate from the end of the raw input.

     void (*ucom_write)(void *sc, int portno, u_char *dst, u_char *src,
             uint32_t *count)
             if the data written to the bulk pipe is not just the raw charac-
             ters then this routine needs to copy count raw characters from
             src into the buffer at dst and do the appropriate padding.  The
             count should be updated to the new size.  The buffer at src is at
             most ibufsize bytes and the buffer at dst is ibufsizepad bytes.

     Apart from these methods there is a function

          void ucom_status_change(struct ucom_softc *)

     which should be called by the driver whenever it notices a status change.


SEE ALSO

     tty(4), uftdi(4), umodem(4), usb(4), uvisor(4)


HISTORY

     This ucom interface first appeared in NetBSD 1.5.

NetBSD 7.0                       July 9, 2012                       NetBSD 7.0