docs: serial: convert docs to ReST and rename to *.rst

The converted files are focused at the Kernel internal API,
so, this is a good candidate for the kernel API set of books.

The conversion is actually:
  - add blank lines and identation in order to identify paragraphs;
  - fix tables markups;
  - add some lists markups;
  - mark literal blocks;
  - adjust title markups.

At its new index.rst, let's add a :orphan: while this is not linked to
the main index.rst file, in order to avoid build warnings.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 0 insertions, 486 deletions

diff --git a/Documentation/serial/driver b/Documentation/serial/driver
deleted file mode 100644
index 86e47c19a924..000000000000
--- a/Documentation/serial/driver
+++ /dev/null
@@ -1,486 +0,0 @@
-
-			Low Level Serial API
-			--------------------
-
-
-This document is meant as a brief overview of some aspects of the new serial
-driver.  It is not complete, any questions you have should be directed to
-<rmk@arm.linux.org.uk>
-
-The reference implementation is contained within amba-pl011.c.
-
-
-
-Low Level Serial Hardware Driver
---------------------------------
-
-The low level serial hardware driver is responsible for supplying port
-information (defined by uart_port) and a set of control methods (defined
-by uart_ops) to the core serial driver.  The low level driver is also
-responsible for handling interrupts for the port, and providing any
-console support.
-
-
-Console Support
----------------
-
-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).
-
-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.
-
-
-Locking
--------
-
-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.)
-
-There are two locks.  A per-port spinlock, and an overall semaphore.
-
-From the core driver perspective, the port->lock locks the following
-data:
-
-	port->mctrl
-	port->icount
-	port->state->xmit.head (circ_buf->head)
-	port->state->xmit.tail (circ_buf->tail)
-
-The low level driver is free to use this lock to provide any additional
-locking.
-
-The port_sem semaphore is used to protect against ports being added/
-removed or reconfigured at inappropriate times. Since v2.6.27, this
-semaphore has been the 'mutex' member of the tty_port struct, and
-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)
-		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 Documentation/serial/tty.txt.
-
-	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
-
-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()
-
-Other notes
------------
-
-It is intended some day to drop the 'unused' entries from uart_port, and
-allow low level drivers to register their own individual uart_port's with
-the core.  This will allow drivers to use uart_port as a pointer to a
-structure containing both the uart_port entry with their own extensions,
-thus:
-
-	struct my_port {
-		struct uart_port	port;
-		int			my_stuff;
-	};
-
-Modem control lines via GPIO
-----------------------------
-
-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.