initrd: cast `initrd_start' to `void *'

[deliverable/linux.git] / Documentation / tty.txt

diff --git a/Documentation/tty.txt b/Documentation/tty.txt
index dab56604745df3d8eaefb9daa9b978befbe3aa1c..8e65c4498c521259d93061e0a94a2d3652eaef98 100644 (file)
--- a/Documentation/tty.txt
+++ b/Documentation/tty.txt
@@ -39,28 +39,37 @@ Line Discipline Methods
 
 TTY side interfaces:
 
 
 TTY side interfaces:
 

+open()         -       Called when the line discipline is attached to
+                       the terminal. No other call into the line
+                       discipline for this tty will occur until it
+                       completes successfully. Can sleep.
+

 close()                -       This is called on a terminal when the line
                        discipline is being unplugged. At the point of
                        execution no further users will enter the
                        ldisc code for this tty. Can sleep.
 
 close()                -       This is called on a terminal when the line
                        discipline is being unplugged. At the point of
                        execution no further users will enter the
                        ldisc code for this tty. Can sleep.
 

-open()         -       Called when the line discipline is attached to
-                       the terminal. No other call into the line
-                       discipline for this tty will occur until it
-                       completes successfully. Can sleep.
+hangup()       -       Called when the tty line is hung up.
+                       The line discipline should cease I/O to the tty.
+                       No further calls into the ldisc code will occur.
+                       Can sleep.

 
 write()                -       A process is writing data through the line
                        discipline.  Multiple write calls are serialized
                        by the tty layer for the ldisc.  May sleep. 
 
 
 write()                -       A process is writing data through the line
                        discipline.  Multiple write calls are serialized
                        by the tty layer for the ldisc.  May sleep. 
 

-flush_buffer() -       May be called at any point between open and close.
+flush_buffer() -       (optional) May be called at any point between
+                       open and close, and instructs the line discipline
+                       to empty its input buffer.

 
 

-chars_in_buffer() -    Report the number of bytes in the buffer.
+chars_in_buffer() -    (optional) Report the number of bytes in the input
+                       buffer.

 
 

-set_termios()  -       Called on termios structure changes. The caller
-                       passes the old termios data and the current data
-                       is in the tty. Called under the termios semaphore so
-                       allowed to sleep. Serialized against itself only.
+set_termios()  -       (optional) Called on termios structure changes.
+                       The caller passes the old termios data and the
+                       current data is in the tty. Called under the
+                       termios semaphore so allowed to sleep. Serialized
+                       against itself only.

 
 read()         -       Move data from the line discipline to the user.
                        Multiple read calls may occur in parallel and the
 
 read()         -       Move data from the line discipline to the user.
                        Multiple read calls may occur in parallel and the


@@ -92,6 +101,98 @@ write_wakeup()      -       May be called at any point between open and close.
                        this function. In such a situation defer it.
 
 
                        this function. In such a situation defer it.
 
 

+Driver Access
+
+Line discipline methods can call the following methods of the underlying
+hardware driver through the function pointers within the tty->driver
+structure:
+
+write()                        Write a block of characters to the tty device.
+                       Returns the number of characters accepted. The
+                       character buffer passed to this method is already
+                       in kernel space.
+
+put_char()             Queues a character for writing to the tty device.
+                       If there is no room in the queue, the character is
+                       ignored.
+
+flush_chars()          (Optional) If defined, must be called after
+                       queueing characters with put_char() in order to
+                       start transmission.
+
+write_room()           Returns the numbers of characters the tty driver
+                       will accept for queueing to be written.
+
+ioctl()                        Invoke device specific ioctl.
+                       Expects data pointers to refer to userspace.
+                       Returns ENOIOCTLCMD for unrecognized ioctl numbers.
+
+set_termios()          Notify the tty driver that the device's termios
+                       settings have changed. New settings are in
+                       tty->termios. Previous settings should be passed in
+                       the "old" argument.
+
+                       The API is defined such that the driver should return
+                       the actual modes selected. This means that the
+                       driver function is responsible for modifying any
+                       bits in the request it cannot fulfill to indicate
+                       the actual modes being used. A device with no
+                       hardware capability for change (eg a USB dongle or
+                       virtual port) can provide NULL for this method.
+
+throttle()             Notify the tty 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 tty.
+
+unthrottle()           Notify the tty driver that characters can now be
+                       sent to the tty without fear of overrunning the
+                       input buffers of the line disciplines.
+
+stop()                 Ask the tty driver to stop outputting characters
+                       to the tty device.
+
+start()                        Ask the tty driver to resume sending characters
+                       to the tty device.
+
+hangup()               Ask the tty driver to hang up the tty device.
+
+break_ctl()            (Optional) Ask the tty driver to turn on or off
+                       BREAK status on the RS-232 port.  If state is -1,
+                       then the BREAK status should be turned on; if
+                       state is 0, then BREAK should be turned off.
+                       If this routine is not implemented, use ioctls
+                       TIOCSBRK / TIOCCBRK instead.
+
+wait_until_sent()      Waits until the device has written out all of the
+                       characters in its transmitter FIFO.
+
+send_xchar()           Send a high-priority XON/XOFF character to the device.
+
+
+Flags
+
+Line discipline methods have access to tty->flags field containing the
+following interesting flags:
+
+TTY_THROTTLED          Driver input is throttled. The ldisc should call
+                       tty->driver->unthrottle() in order to resume
+                       reception when it is ready to process more data.
+
+TTY_DO_WRITE_WAKEUP    If set, causes the driver to call the ldisc's
+                       write_wakeup() method in order to resume
+                       transmission when it can accept more data
+                       to transmit.
+
+TTY_IO_ERROR           If set, causes all subsequent userspace read/write
+                       calls on the tty to fail, returning -EIO.
+
+TTY_OTHER_CLOSED       Device is a pty and the other side has closed.
+
+TTY_NO_WRITE_SPLIT     Prevent driver from splitting up writes into
+                       smaller chunks.
+
+

 Locking
 
 Callers to the line discipline functions from the tty layer are required to
 Locking
 
 Callers to the line discipline functions from the tty layer are required to