Merge remote-tracking branch 'nvdimm/libnvdimm-for-next'

[karo-tx-linux.git] / Documentation / serial / tty.txt

diff --git a/Documentation/serial/tty.txt b/Documentation/serial/tty.txt
index 973c8ad3f959fba7f722aafa6c89c5b29c40aaa9..bc3842dc323a629fae6ec4cf5de0f6d1d6d6f37d 100644 (file)
--- a/Documentation/serial/tty.txt
+++ b/Documentation/serial/tty.txt
@@ -39,8 +39,13 @@ 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
 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. Returning an error will
-                       prevent the ldisc from being attached. Can sleep.
+                       completes successfully. Should initialize any
+                       state needed by the ldisc, and set receive_room
+                       in the tty_struct to the maximum amount of data
+                       the line discipline is willing to accept from the
+                       driver with a single call to receive_buf().
+                       Returning an error will prevent the ldisc from
+                       being attached. Can sleep.

 
 close()                -       This is called on a terminal when the line
                        discipline is being unplugged. At the point of
 
 close()                -       This is called on a terminal when the line
                        discipline is being unplugged. At the point of


@@ -52,9 +57,16 @@ hangup()     -       Called when the tty line is hung up.
                        No further calls into the ldisc code will occur.
                        The return value is ignored. Can sleep.
 
                        No further calls into the ldisc code will occur.
                        The return value is ignored. 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. 
+read()         -       (optional) A process requests reading data from
+                       the line. Multiple read calls may occur in parallel
+                       and the ldisc must deal with serialization issues.
+                       If not defined, the process will receive an EIO
+                       error. May sleep.
+
+write()                -       (optional) A process requests writing data to the
+                       line. Multiple write calls are serialized by the
+                       tty layer for the ldisc. If not defined, the
+                       process will receive an EIO error. May sleep.

 
 flush_buffer() -       (optional) May be called at any point between
                        open and close, and instructs the line discipline
 
 flush_buffer() -       (optional) May be called at any point between
                        open and close, and instructs the line discipline


@@ -69,27 +81,33 @@ set_termios()       -       (optional) Called on termios structure changes.
                        termios semaphore so allowed to sleep. Serialized
                        against itself only.
 
                        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
-                       ldisc must deal with serialization issues. May 
-                       sleep.
-
-poll()         -       Check the status for the poll/select calls. Multiple
-                       poll calls may occur in parallel. May sleep.
+poll()         -       (optional) Check the status for the poll/select
+                       calls. Multiple poll calls may occur in parallel.
+                       May sleep.

 
 

-ioctl()                -       Called when an ioctl is handed to the tty layer
-                       that might be for the ldisc. Multiple ioctl calls
-                       may occur in parallel. May sleep. 
+ioctl()                -       (optional) Called when an ioctl is handed to the
+                       tty layer that might be for the ldisc. Multiple
+                       ioctl calls may occur in parallel. May sleep.

 
 

-compat_ioctl() -       Called when a 32 bit ioctl is handed to the tty layer
-                       that might be for the ldisc. Multiple ioctl calls
-                       may occur in parallel. May sleep.
+compat_ioctl() -       (optional) Called when a 32 bit ioctl is handed
+                       to the tty layer that might be for the ldisc.
+                       Multiple ioctl calls may occur in parallel.
+                       May sleep.

 
 Driver Side Interfaces:
 
 
 Driver Side Interfaces:
 

-receive_buf()  -       Hand buffers of bytes from the driver to the ldisc
-                       for processing. Semantics currently rather
-                       mysterious 8(
+receive_buf()  -       (optional) Called by the low-level driver to hand
+                       a buffer of received bytes to the ldisc for
+                       processing. The number of bytes is guaranteed not
+                       to exceed the current value of tty->receive_room.
+                       All bytes must be processed.
+
+receive_buf2() -       (optional) Called by the low-level driver to hand
+                       a buffer of received bytes to the ldisc for
+                       processing. Returns the number of bytes processed.
+
+                       If both receive_buf() and receive_buf2() are
+                       defined, receive_buf2() should be preferred.

 
 write_wakeup() -       May be called at any point between open and close.
                        The TTY_DO_WRITE_WAKEUP flag indicates if a call
 
 write_wakeup() -       May be called at any point between open and close.
                        The TTY_DO_WRITE_WAKEUP flag indicates if a call