---------------
The serial core provides a few helper functions. This includes identifing
-the correct port structure (via uart_get_console) and decoding command line
-arguments (uart_parse_options).
+the correct port structure (via uart_get_console()) and decoding command line
+arguments (uart_parse_options()).
-There is also a helper function (uart_console_write) which performs a
+There is also a helper function (uart_console_write()) which performs a
character by character write, translating newlines to CRLF sequences.
Driver writers are recommended to use this function rather than implementing
their own version.
It is the responsibility of the low level hardware driver to perform the
necessary locking using port->lock. There are some exceptions (which
-are described in the uart_ops listing below.)
+are described in the struct uart_ops listing below.)
There are two locks. A per-port spinlock, and an overall semaphore.
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)
- 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
---------------
-uart_update_timeout(port,cflag,baud)
- Update the FIFO drain timeout, port->timeout, according to the
- number of bits, parity, stop bits and baud rate.
-
- Locking: caller is expected to take port->lock
-
- Interrupts: n/a
-
-uart_get_baud_rate(port,termios,old,min,max)
- Return the numeric baud rate for the specified termios, taking
- account of the special 38400 baud "kludge". The B0 baud rate
- is mapped to 9600 baud.
-
- If the baud rate is not within min..max, then if old is non-NULL,
- the original baud rate will be tried. If that exceeds the
- min..max constraint, 9600 baud will be returned. termios will
- be updated to the baud rate in use.
-
- Note: min..max must always allow 9600 baud to be selected.
-
- Locking: caller dependent.
-
- Interrupts: n/a
-
-uart_get_divisor(port,baud)
- Return the divisor (baud_base / baud) for the specified baud
- rate, appropriately rounded.
-
- If 38400 baud and custom divisor is selected, return the
- custom divisor instead.
-
- Locking: caller dependent.
-
- Interrupts: n/a
-
-uart_match_port(port1,port2)
- This utility function can be used to determine whether two
- uart_port structures describe the same port.
-
- Locking: n/a
-
- Interrupts: n/a
-
-uart_write_wakeup(port)
- A driver is expected to call this function when the number of
- characters in the transmit buffer have dropped below a threshold.
-
- Locking: port->lock should be held.
-
- Interrupts: n/a
-
-uart_register_driver(drv)
- Register a uart driver with the core driver. We in turn register
- with the tty layer, and initialise the core driver per-port state.
-
- drv->port should be NULL, and the per-port structures should be
- registered using uart_add_one_port after this call has succeeded.
-
- Locking: none
-
- Interrupts: enabled
-
-uart_unregister_driver()
- Remove all references to a driver from the core driver. The low
- level driver must have removed all its ports via the
- uart_remove_one_port() if it registered them with uart_add_one_port().
-
- Locking: none
-
- Interrupts: enabled
-
-**uart_suspend_port()**
-
-**uart_resume_port()**
-
-**uart_add_one_port()**
-
-**uart_remove_one_port()**
+.. kernel-doc:: drivers/tty/serial/serial_core.c
+ :identifiers: uart_update_timeout uart_get_baud_rate uart_get_divisor
+ uart_match_port uart_write_wakeup uart_register_driver
+ uart_unregister_driver uart_suspend_port uart_resume_port
+ uart_add_one_port uart_remove_one_port uart_console_write
+ uart_parse_earlycon uart_parse_options uart_set_options
+ uart_get_lsr_info uart_handle_dcd_change uart_handle_cts_change
+ uart_try_toggle_sysrq uart_get_console
Other notes
-----------
Some helpers are provided in order to set/get modem control lines via GPIO.
-mctrl_gpio_init(port, idx):
- This will get the {cts,rts,...}-gpios from device tree if they are
- present and request them, set direction etc, and return an
- allocated structure. `devm_*` functions are used, so there's no need
- to call mctrl_gpio_free().
- As this sets up the irq handling make sure to not handle changes to the
- gpio input lines in your driver, too.
-
-mctrl_gpio_free(dev, gpios):
- This will free the requested gpios in mctrl_gpio_init().
- As `devm_*` functions are used, there's generally no need to call
- this function.
-
-mctrl_gpio_to_gpiod(gpios, gidx)
- This returns the gpio_desc structure associated to the modem line
- index.
-
-mctrl_gpio_set(gpios, mctrl):
- This will sets the gpios according to the mctrl state.
-
-mctrl_gpio_get(gpios, mctrl):
- This will update mctrl with the gpios values.
-
-mctrl_gpio_enable_ms(gpios):
- Enables irqs and handling of changes to the ms lines.
-
-mctrl_gpio_disable_ms(gpios):
- Disables irqs and handling of changes to the ms lines.
+.. kernel-doc:: drivers/tty/serial/serial_mctrl_gpio.c
+ :identifiers: mctrl_gpio_init mctrl_gpio_free mctrl_gpio_to_gpiod
+ mctrl_gpio_set mctrl_gpio_get mctrl_gpio_enable_ms
+ mctrl_gpio_disable_ms
projects / linux-2.6-microblaze.git / blobdiff