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Documentation: improve line discipline method descriptions
Mention that the ldisc open method must set tty->receive_room, and
that many methods are optional. Add description of receive_buf2 method.
Signed-off-by: Tilman Schmidt <tilman@imap.cc>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
authored by
Tilman Schmidt
and committed by
Greg Kroah-Hartman
1a76eb5b
850b37a7
+39
-21
+39
-21
Documentation/serial/tty.txt
+39
-21
Documentation/serial/tty.txt
···
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open() - Called when the line discipline is attached to
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the terminal. No other call into the line
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discipline for this tty will occur until it
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completes successfully. Returning an error will
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prevent the ldisc from being attached. Can sleep.
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completes successfully. Should initialize any
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state needed by the ldisc, and set receive_room
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in the tty_struct to the maximum amount of data
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the line discipline is willing to accept from the
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driver with a single call to receive_buf().
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Returning an error will prevent the ldisc from
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being attached. Can sleep.
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close() - This is called on a terminal when the line
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discipline is being unplugged. At the point of
···
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No further calls into the ldisc code will occur.
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The return value is ignored. Can sleep.
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-
write() - A process is writing data through the line
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discipline. Multiple write calls are serialized
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by the tty layer for the ldisc. May sleep.
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read() - (optional) A process requests reading data from
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the line. Multiple read calls may occur in parallel
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and the ldisc must deal with serialization issues.
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If not defined, the process will receive an EIO
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error. May sleep.
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write() - (optional) A process requests writing data to the
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line. Multiple write calls are serialized by the
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tty layer for the ldisc. If not defined, the
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process will receive an EIO error. May sleep.
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flush_buffer() - (optional) May be called at any point between
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open and close, and instructs the line discipline
···
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termios semaphore so allowed to sleep. Serialized
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against itself only.
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read() - Move data from the line discipline to the user.
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Multiple read calls may occur in parallel and the
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ldisc must deal with serialization issues. May
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sleep.
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poll() - (optional) Check the status for the poll/select
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calls. Multiple poll calls may occur in parallel.
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May sleep.
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poll() - Check the status for the poll/select calls. Multiple
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poll calls may occur in parallel. May sleep.
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ioctl() - (optional) Called when an ioctl is handed to the
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tty layer that might be for the ldisc. Multiple
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ioctl calls may occur in parallel. May sleep.
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ioctl() - Called when an ioctl is handed to the tty layer
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that might be for the ldisc. Multiple ioctl calls
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may occur in parallel. May sleep.
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-
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compat_ioctl() - Called when a 32 bit ioctl is handed to the tty layer
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that might be for the ldisc. Multiple ioctl calls
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may occur in parallel. May sleep.
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compat_ioctl() - (optional) Called when a 32 bit ioctl is handed
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to the tty layer that might be for the ldisc.
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Multiple ioctl calls may occur in parallel.
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May sleep.
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Driver Side Interfaces:
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receive_buf() - Hand buffers of bytes from the driver to the ldisc
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for processing. Semantics currently rather
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mysterious 8(
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receive_buf() - (optional) Called by the low-level driver to hand
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a buffer of received bytes to the ldisc for
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processing. The number of bytes is guaranteed not
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to exceed the current value of tty->receive_room.
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All bytes must be processed.
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receive_buf2() - (optional) Called by the low-level driver to hand
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a buffer of received bytes to the ldisc for
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processing. Returns the number of bytes processed.
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If both receive_buf() and receive_buf2() are
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defined, receive_buf2() should be preferred.
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write_wakeup() - May be called at any point between open and close.
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The TTY_DO_WRITE_WAKEUP flag indicates if a call