diff options
Diffstat (limited to 'Documentation/driver-api')
| -rw-r--r-- | Documentation/driver-api/serial/driver.rst | 358 |
1 files changed, 2 insertions, 356 deletions
diff --git a/Documentation/driver-api/serial/driver.rst b/Documentation/driver-api/serial/driver.rst index ee1679858aa2..cb0ec6db4f1e 100644 --- a/Documentation/driver-api/serial/driver.rst +++ b/Documentation/driver-api/serial/driver.rst @@ -63,362 +63,8 @@ commonly referred to as the port mutex. uart_ops -------- -The uart_ops structure is the main interface between serial_core and the -hardware specific driver. It contains all the methods to control the -hardware. - - tx_empty(port) - This function tests whether the transmitter fifo and shifter - for the port described by 'port' is empty. If it is empty, - this function should return TIOCSER_TEMT, otherwise return 0. - If the port does not support this operation, then it should - return TIOCSER_TEMT. - - Locking: none. - - Interrupts: caller dependent. - - This call must not sleep - - set_mctrl(port, mctrl) - This function sets the modem control lines for port described - by 'port' to the state described by mctrl. The relevant bits - of mctrl are: - - - TIOCM_RTS RTS signal. - - TIOCM_DTR DTR signal. - - TIOCM_OUT1 OUT1 signal. - - TIOCM_OUT2 OUT2 signal. - - TIOCM_LOOP Set the port into loopback mode. - - If the appropriate bit is set, the signal should be driven - active. If the bit is clear, the signal should be driven - inactive. - - Locking: port->lock taken. - - Interrupts: locally disabled. - - This call must not sleep - - get_mctrl(port) - Returns the current state of modem control inputs. The state - of the outputs should not be returned, since the core keeps - track of their state. The state information should include: - - - TIOCM_CAR state of DCD signal - - TIOCM_CTS state of CTS signal - - TIOCM_DSR state of DSR signal - - TIOCM_RI state of RI signal - - The bit is set if the signal is currently driven active. If - the port does not support CTS, DCD or DSR, the driver should - indicate that the signal is permanently active. If RI is - not available, the signal should not be indicated as active. - - Locking: port->lock taken. - - Interrupts: locally disabled. - - This call must not sleep - - stop_tx(port) - Stop transmitting characters. This might be due to the CTS - line becoming inactive or the tty layer indicating we want - to stop transmission due to an XOFF character. - - The driver should stop transmitting characters as soon as - possible. - - Locking: port->lock taken. - - Interrupts: locally disabled. - - This call must not sleep - - start_tx(port) - Start transmitting characters. - - Locking: port->lock taken. - - Interrupts: locally disabled. - - This call must not sleep - - throttle(port) - Notify the serial driver that input buffers for the line discipline are - close to full, and it should somehow signal that no more characters - should be sent to the serial port. - This will be called only if hardware assisted flow control is enabled. - - Locking: serialized with .unthrottle() and termios modification by the - tty layer. - - unthrottle(port) - Notify the serial driver that characters can now be sent to the serial - port without fear of overrunning the input buffers of the line - disciplines. - - This will be called only if hardware assisted flow control is enabled. - - Locking: serialized with .throttle() and termios modification by the - tty layer. - - send_xchar(port,ch) - Transmit a high priority character, even if the port is stopped. - This is used to implement XON/XOFF flow control and tcflow(). If - the serial driver does not implement this function, the tty core - will append the character to the circular buffer and then call - start_tx() / stop_tx() to flush the data out. - - Do not transmit if ch == '\0' (__DISABLED_CHAR). - - Locking: none. - - Interrupts: caller dependent. - - stop_rx(port) - Stop receiving characters; the port is in the process of - being closed. - - Locking: port->lock taken. - - Interrupts: locally disabled. - - This call must not sleep - - enable_ms(port) - Enable the modem status interrupts. - - This method may be called multiple times. Modem status - interrupts should be disabled when the shutdown method is - called. - - Locking: port->lock taken. - - Interrupts: locally disabled. - - This call must not sleep - - break_ctl(port,ctl) - Control the transmission of a break signal. If ctl is - nonzero, the break signal should be transmitted. The signal - should be terminated when another call is made with a zero - ctl. - - Locking: caller holds tty_port->mutex - - startup(port) - Grab any interrupt resources and initialise any low level driver - state. Enable the port for reception. It should not activate - RTS nor DTR; this will be done via a separate call to set_mctrl. - - This method will only be called when the port is initially opened. - - Locking: port_sem taken. - - Interrupts: globally disabled. - - shutdown(port) - Disable the port, disable any break condition that may be in - effect, and free any interrupt resources. It should not disable - RTS nor DTR; this will have already been done via a separate - call to set_mctrl. - - Drivers must not access port->state once this call has completed. - - This method will only be called when there are no more users of - this port. - - Locking: port_sem taken. - - Interrupts: caller dependent. - - flush_buffer(port) - Flush any write buffers, reset any DMA state and stop any - ongoing DMA transfers. - - This will be called whenever the port->state->xmit circular - buffer is cleared. - - Locking: port->lock taken. - - Interrupts: locally disabled. - - This call must not sleep - - set_termios(port,termios,oldtermios) - Change the port parameters, including word length, parity, stop - bits. Update read_status_mask and ignore_status_mask to indicate - the types of events we are interested in receiving. Relevant - termios->c_cflag bits are: - - CSIZE - - word size - CSTOPB - - 2 stop bits - PARENB - - parity enable - PARODD - - odd parity (when PARENB is in force) - ADDRB - - address bit (changed through .rs485_config()). - CREAD - - enable reception of characters (if not set, - still receive characters from the port, but - throw them away. - CRTSCTS - - if set, enable CTS status change reporting - CLOCAL - - if not set, enable modem status change - reporting. - - Relevant termios->c_iflag bits are: - - INPCK - - enable frame and parity error events to be - passed to the TTY layer. - BRKINT / PARMRK - - both of these enable break events to be - passed to the TTY layer. - - IGNPAR - - ignore parity and framing errors - IGNBRK - - ignore break errors, If IGNPAR is also - set, ignore overrun errors as well. - - The interaction of the iflag bits is as follows (parity error - given as an example): - - =============== ======= ====== ============================= - Parity error INPCK IGNPAR - =============== ======= ====== ============================= - n/a 0 n/a character received, marked as - TTY_NORMAL - None 1 n/a character received, marked as - TTY_NORMAL - Yes 1 0 character received, marked as - TTY_PARITY - Yes 1 1 character discarded - =============== ======= ====== ============================= - - Other flags may be used (eg, xon/xoff characters) if your - hardware supports hardware "soft" flow control. - - Locking: caller holds tty_port->mutex - - Interrupts: caller dependent. - - This call must not sleep - - set_ldisc(port,termios) - Notifier for discipline change. See ../tty/tty_ldisc.rst. - - Locking: caller holds tty_port->mutex - - pm(port,state,oldstate) - Perform any power management related activities on the specified - port. State indicates the new state (defined by - enum uart_pm_state), oldstate indicates the previous state. - - This function should not be used to grab any resources. - - This will be called when the port is initially opened and finally - closed, except when the port is also the system console. This - will occur even if CONFIG_PM is not set. - - Locking: none. - - Interrupts: caller dependent. - - type(port) - Return a pointer to a string constant describing the specified - port, or return NULL, in which case the string 'unknown' is - substituted. - - Locking: none. - - Interrupts: caller dependent. - - release_port(port) - Release any memory and IO region resources currently in use by - the port. - - Locking: none. - - Interrupts: caller dependent. - - request_port(port) - Request any memory and IO region resources required by the port. - If any fail, no resources should be registered when this function - returns, and it should return -EBUSY on failure. - - Locking: none. - - Interrupts: caller dependent. - - config_port(port,type) - Perform any autoconfiguration steps required for the port. `type` - contains a bit mask of the required configuration. UART_CONFIG_TYPE - indicates that the port requires detection and identification. - port->type should be set to the type found, or PORT_UNKNOWN if - no port was detected. - - UART_CONFIG_IRQ indicates autoconfiguration of the interrupt signal, - which should be probed using standard kernel autoprobing techniques. - This is not necessary on platforms where ports have interrupts - internally hard wired (eg, system on a chip implementations). - - Locking: none. - - Interrupts: caller dependent. - - verify_port(port,serinfo) - Verify the new serial port information contained within serinfo is - suitable for this port type. - - Locking: none. - - Interrupts: caller dependent. - - ioctl(port,cmd,arg) - Perform any port specific IOCTLs. IOCTL commands must be defined - using the standard numbering system found in <asm/ioctl.h> - - Locking: none. - - Interrupts: caller dependent. - - poll_init(port) - Called by kgdb to perform the minimal hardware initialization needed - to support poll_put_char() and poll_get_char(). Unlike ->startup() - this should not request interrupts. - - Locking: tty_mutex and tty_port->mutex taken. - - Interrupts: n/a. - - poll_put_char(port,ch) - Called by kgdb to write a single character directly to the serial - port. It can and should block until there is space in the TX FIFO. - - Locking: none. - - Interrupts: caller dependent. - - This call must not sleep - - poll_get_char(port) - Called by kgdb to read a single character directly from the serial - port. If data is available, it should be returned; otherwise - the function should return NO_POLL_CHAR immediately. - - Locking: none. - - Interrupts: caller dependent. - - This call must not sleep +.. kernel-doc:: include/linux/serial_core.h + :identifiers: uart_ops Other functions --------------- |