tty: add kernel-doc for tty_ldisc_ops

tty_ldisc_ops structure was already partially documented in a standalone
comment in the header beginning.

Move it right before the structure and reformat it so it complies to
kernel-doc. That way, we can include it in Documentation/ later in this
series.

And add the documentation for the members where missing too.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20211126081611.11001-7-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/tty_ldisc.h

@@ -4,126 +4,6 @@
 
 struct tty_struct;
 
-/*
- * This structure defines the interface between the tty line discipline
- * implementation and the tty routines.  The following routines can be
- * defined; unless noted otherwise, they are optional, and can be
- * filled in with a null pointer.
- *
- * int	(*open)(struct tty_struct *);
- *
- *	This function is called when the line discipline is associated
- *	with the tty.  The line discipline can use this as an
- *	opportunity to initialize any state needed by the ldisc routines.
- *
- * void	(*close)(struct tty_struct *);
- *
- *	This function is called when the line discipline is being
- *	shutdown, either because the tty is being closed or because
- *	the tty is being changed to use a new line discipline
- *
- * void	(*flush_buffer)(struct tty_struct *tty);
- *
- *	This function instructs the line discipline to clear its
- *	buffers of any input characters it may have queued to be
- *	delivered to the user mode process.
- *
- * ssize_t (*read)(struct tty_struct * tty, struct file * file,
- *		   unsigned char * buf, size_t nr);
- *
- *	This function is called when the user requests to read from
- *	the tty.  The line discipline will return whatever characters
- *	it has buffered up for the user.  If this function is not
- *	defined, the user will receive an EIO error.
- *
- * ssize_t (*write)(struct tty_struct * tty, struct file * file,
- *		    const unsigned char * buf, size_t nr);
- *
- *	This function is called when the user requests to write to the
- *	tty.  The line discipline will deliver the characters to the
- *	low-level tty device for transmission, optionally performing
- *	some processing on the characters first.  If this function is
- *	not defined, the user will receive an EIO error.
- *
- * int	(*ioctl)(struct tty_struct *tty, unsigned int cmd, unsigned long arg);
- *
- *	This function is called when the user requests an ioctl which
- *	is not handled by the tty layer or the low-level tty driver.
- *	It is intended for ioctls which affect line discpline
- *	operation.  Note that the search order for ioctls is (1) tty
- *	layer, (2) tty low-level driver, (3) line discpline.  So a
- *	low-level driver can "grab" an ioctl request before the line
- *	discpline has a chance to see it.
- *
- * int	(*compat_ioctl)(struct tty_struct *tty, unsigned int cmd,
- *			unsigned long arg);
- *
- *	Process ioctl calls from 32-bit process on 64-bit system
- *
- *	NOTE: only ioctls that are neither "pointer to compatible
- *	structure" nor tty-generic.  Something private that takes
- *	an integer or a pointer to wordsize-sensitive structure
- *	belongs here, but most of ldiscs will happily leave
- *	it NULL.
- *
- * void	(*set_termios)(struct tty_struct *tty, struct ktermios * old);
- *
- *	This function notifies the line discpline that a change has
- *	been made to the termios structure.
- *
- * int	(*poll)(struct tty_struct * tty, struct file * file,
- *		  poll_table *wait);
- *
- *	This function is called when a user attempts to select/poll on a
- *	tty device.  It is solely the responsibility of the line
- *	discipline to handle poll requests.
- *
- * void	(*receive_buf)(struct tty_struct *, const unsigned char *cp,
- *		       char *fp, int count);
- *
- *	This function is called by the low-level tty driver to send
- *	characters received by the hardware to the line discpline for
- *	processing.  <cp> is a pointer to the buffer of input
- *	character received by the device.  <fp> is a pointer to a
- *	pointer of flag bytes which indicate whether a character was
- *	received with a parity error, etc. <fp> may be NULL to indicate
- *	all data received is TTY_NORMAL.
- *
- * void	(*write_wakeup)(struct tty_struct *);
- *
- *	This function is called by the low-level tty driver to signal
- *	that line discpline should try to send more characters to the
- *	low-level driver for transmission.  If the line discpline does
- *	not have any more data to send, it can just return. If the line
- *	discipline does have some data to send, please arise a tasklet
- *	or workqueue to do the real data transfer. Do not send data in
- *	this hook, it may leads to a deadlock.
- *
- * int (*hangup)(struct tty_struct *)
- *
- *	Called on a hangup. Tells the discipline that it should
- *	cease I/O to the tty driver. Can sleep. The driver should
- *	seek to perform this action quickly but should wait until
- *	any pending driver I/O is completed.
- *
- * void (*dcd_change)(struct tty_struct *tty, unsigned int status)
- *
- *	Tells the discipline that the DCD pin has changed its status.
- *	Used exclusively by the N_PPS (Pulse-Per-Second) line discipline.
- *
- * int	(*receive_buf2)(struct tty_struct *, const unsigned char *cp,
- *			char *fp, int count);
- *
- *	This function is called by the low-level tty driver to send
- *	characters received by the hardware to the line discpline for
- *	processing.  <cp> is a pointer to the buffer of input
- *	character received by the device.  <fp> is a pointer to a
- *	pointer of flag bytes which indicate whether a character was
- *	received with a parity error, etc. <fp> may be NULL to indicate
- *	all data received is TTY_NORMAL.
- *	If assigned, prefer this function for automatic flow control.
- */
-
 #include <linux/fs.h>
 #include <linux/wait.h>
 #include <linux/atomic.h>
@@ -175,7 +55,128 @@ int ldsem_down_write_nested(struct ld_semaphore *sem, int subclass,
 		ldsem_down_write(sem, timeout)
 #endif
 
-
+/**
+ * struct tty_ldisc_ops - ldisc operations
+ *
+ * @name: name of this ldisc rendered in /proc/tty/ldiscs
+ * @num: ``N_*`` number (%N_TTY, %N_HDLC, ...) reserved to this ldisc
+ *
+ * @open: ``int ()(struct tty_struct *tty)``
+ *
+ *	This function is called when the line discipline is associated with the
+ *	@tty. The line discipline can use this as an opportunity to initialize
+ *	any state needed by the ldisc routines.
+ *
+ * @close: ``void ()(struct tty_struct *tty)``
+ *
+ *	This function is called when the line discipline is being shutdown,
+ *	either because the @tty is being closed or because the @tty is being
+ *	changed to use a new line discipline
+ *
+ * @flush_buffer: ``void ()(struct tty_struct *tty)``
+ *
+ *	This function instructs the line discipline to clear its buffers of any
+ *	input characters it may have queued to be delivered to the user mode
+ *	process.
+ *
+ * @read: ``ssize_t ()(struct tty_struct *tty, struct file *file,
+ *		unsigned char *buf, size_t nr)``
+ *
+ *	This function is called when the user requests to read from the @tty.
+ *	The line discipline will return whatever characters it has buffered up
+ *	for the user. If this function is not defined, the user will receive
+ *	an %EIO error.
+ *
+ * @write: ``ssize_t ()(struct tty_struct *tty, struct file *file,
+ *		const unsigned char *buf, size_t nr)``
+ *
+ *	This function is called when the user requests to write to the @tty.
+ *	The line discipline will deliver the characters to the low-level tty
+ *	device for transmission, optionally performing some processing on the
+ *	characters first. If this function is not defined, the user will
+ *	receive an %EIO error.
+ *
+ * @ioctl: ``int ()(struct tty_struct *tty, unsigned int cmd,
+ *		unsigned long arg)``
+ *
+ *	This function is called when the user requests an ioctl which is not
+ *	handled by the tty layer or the low-level tty driver. It is intended
+ *	for ioctls which affect line discpline operation.  Note that the search
+ *	order for ioctls is (1) tty layer, (2) tty low-level driver, (3) line
+ *	discpline. So a low-level driver can "grab" an ioctl request before
+ *	the line discpline has a chance to see it.
+ *
+ * @compat_ioctl: ``int ()(struct tty_struct *tty, unsigned int cmd,
+ *		unsigned long arg)``
+ *
+ *	Process ioctl calls from 32-bit process on 64-bit system.
+ *
+ *	Note that only ioctls that are neither "pointer to compatible
+ *	structure" nor tty-generic.  Something private that takes an integer or
+ *	a pointer to wordsize-sensitive structure belongs here, but most of
+ *	ldiscs will happily leave it %NULL.
+ *
+ * @set_termios: ``void ()(struct tty_struct *tty, struct ktermios *old)``
+ *
+ *	This function notifies the line discpline that a change has been made
+ *	to the termios structure.
+ *
+ * @poll: ``int ()(struct tty_struct *tty, struct file *file,
+ *		  struct poll_table_struct *wait)``
+ *
+ *	This function is called when a user attempts to select/poll on a @tty
+ *	device. It is solely the responsibility of the line discipline to
+ *	handle poll requests.
+ *
+ * @hangup: ``void ()(struct tty_struct *tty)``
+ *
+ *	Called on a hangup. Tells the discipline that it should cease I/O to
+ *	the tty driver. Can sleep. The driver should seek to perform this
+ *	action quickly but should wait until any pending driver I/O is
+ *	completed.
+ *
+ * @receive_buf: ``void ()(struct tty_struct *tty, const unsigned char *cp,
+ *		       const char *fp, int count)``
+ *
+ *	This function is called by the low-level tty driver to send characters
+ *	received by the hardware to the line discpline for processing. @cp is
+ *	a pointer to the buffer of input character received by the device. @fp
+ *	is a pointer to an array of flag bytes which indicate whether a
+ *	character was received with a parity error, etc. @fp may be %NULL to
+ *	indicate all data received is %TTY_NORMAL.
+ *
+ * @write_wakeup: ``void ()(struct tty_struct *tty)``
+ *
+ *	This function is called by the low-level tty driver to signal that line
+ *	discpline should try to send more characters to the low-level driver
+ *	for transmission. If the line discpline does not have any more data to
+ *	send, it can just return. If the line discipline does have some data to
+ *	send, please arise a tasklet or workqueue to do the real data transfer.
+ *	Do not send data in this hook, it may lead to a deadlock.
+ *
+ * @dcd_change: ``void ()(struct tty_struct *tty, unsigned int status)``
+ *
+ *	Tells the discipline that the DCD pin has changed its status. Used
+ *	exclusively by the %N_PPS (Pulse-Per-Second) line discipline.
+ *
+ * @receive_buf2: ``int ()(struct tty_struct *tty, const unsigned char *cp,
+ *			const char *fp, int count)``
+ *
+ *	This function is called by the low-level tty driver to send characters
+ *	received by the hardware to the line discpline for processing. @cp is a
+ *	pointer to the buffer of input character received by the device.  @fp
+ *	is a pointer to an array of flag bytes which indicate whether a
+ *	character was received with a parity error, etc. @fp may be %NULL to
+ *	indicate all data received is %TTY_NORMAL. If assigned, prefer this
+ *	function for automatic flow control.
+ *
+ * @owner: module containting this ldisc (for reference counting)
+ *
+ * This structure defines the interface between the tty line discipline
+ * implementation and the tty routines. The above routines can be defined.
+ * Unless noted otherwise, they are optional, and can be filled in with a %NULL
+ * pointer.
+ */
 struct tty_ldisc_ops {
 	char	*name;
 	int	num;
@@ -183,8 +184,8 @@ struct tty_ldisc_ops {
 	/*
 	 * The following routines are called from above.
 	 */
-	int	(*open)(struct tty_struct *);
+	int	(*open)(struct tty_struct *tty);
-	void	(*close)(struct tty_struct *);
+	void	(*close)(struct tty_struct *tty);
 	void	(*flush_buffer)(struct tty_struct *tty);
 	ssize_t	(*read)(struct tty_struct *tty, struct file *file,
 			unsigned char *buf, size_t nr,
@@ -196,18 +197,18 @@ struct tty_ldisc_ops {
 	int	(*compat_ioctl)(struct tty_struct *tty, unsigned int cmd,
 			unsigned long arg);
 	void	(*set_termios)(struct tty_struct *tty, struct ktermios *old);
-	__poll_t (*poll)(struct tty_struct *, struct file *,
+	__poll_t (*poll)(struct tty_struct *tty, struct file *file,
-			     struct poll_table_struct *);
+			     struct poll_table_struct *wait);
 	void	(*hangup)(struct tty_struct *tty);
 
 	/*
 	 * The following routines are called from below.
 	 */
-	void	(*receive_buf)(struct tty_struct *, const unsigned char *cp,
+	void	(*receive_buf)(struct tty_struct *tty, const unsigned char *cp,
 			       const char *fp, int count);
-	void	(*write_wakeup)(struct tty_struct *);
+	void	(*write_wakeup)(struct tty_struct *tty);
-	void	(*dcd_change)(struct tty_struct *, unsigned int);
+	void	(*dcd_change)(struct tty_struct *tty, unsigned int status);
-	int	(*receive_buf2)(struct tty_struct *, const unsigned char *cp,
+	int	(*receive_buf2)(struct tty_struct *tty, const unsigned char *cp,
 				const char *fp, int count);
 
 	struct  module *owner;