diff options
| -rw-r--r-- | Documentation/driver-api/serial/tty.rst | 95 | ||||
| -rw-r--r-- | include/linux/tty_ldisc.h | 67 |
2 files changed, 45 insertions, 117 deletions
diff --git a/Documentation/driver-api/serial/tty.rst b/Documentation/driver-api/serial/tty.rst index f7ef10c6f458..333a5923f6e1 100644 --- a/Documentation/driver-api/serial/tty.rst +++ b/Documentation/driver-api/serial/tty.rst @@ -35,99 +35,8 @@ about to enter and exit although this detail matters not). Line Discipline Methods ----------------------- -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. 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 - execution no further users will enter the - ldisc code for this tty. 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. - -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 - to empty its input buffer. - -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. - -poll() (optional) Check the status for the poll/select - calls. Multiple poll 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() (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 -^^^^^^^^^^^^^^^^^^^^^^ - -======================= ======================================================= -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 - is needed but always races versus calls. Thus the - ldisc must be careful about setting order and to - handle unexpected calls. Must not sleep. - - The driver is forbidden from calling this directly - from the ->write call from the ldisc as the ldisc - is permitted to call the driver write method from - this function. In such a situation defer it. - -dcd_change() Report to the tty line the current DCD pin status - changes and the relative timestamp. The timestamp - cannot be NULL. -======================= ======================================================= - +.. kernel-doc:: include/linux/tty_ldisc.h + :identifiers: tty_ldisc_ops Driver Access ^^^^^^^^^^^^^ diff --git a/include/linux/tty_ldisc.h b/include/linux/tty_ldisc.h index e0da0ba02de9..e85002b56752 100644 --- a/include/linux/tty_ldisc.h +++ b/include/linux/tty_ldisc.h @@ -61,33 +61,45 @@ int ldsem_down_write_nested(struct ld_semaphore *sem, int subclass, * @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)`` + * @open: [TTY] ``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. + * @tty. No other call into the line discipline for this tty will occur + * until it completes successfully. It should initialize any state needed + * by the ldisc, and set @tty->receive_room 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. * - * @close: ``void ()(struct tty_struct *tty)`` + * Can sleep. + * + * @close: [TTY] ``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 + * changed to use a new line discipline. At the point of execution no + * further users will enter the ldisc code for this tty. + * + * Can sleep. * - * @flush_buffer: ``void ()(struct tty_struct *tty)`` + * @flush_buffer: [TTY] ``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. + * process. It may be called at any point between open and close. * - * @read: ``ssize_t ()(struct tty_struct *tty, struct file *file, + * @read: [TTY] ``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. + * an %EIO error. Multiple read calls may occur in parallel and the ldisc + * must deal with serialization issues. + * + * Can sleep. * - * @write: ``ssize_t ()(struct tty_struct *tty, struct file *file, + * @write: [TTY] ``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. @@ -96,7 +108,9 @@ int ldsem_down_write_nested(struct ld_semaphore *sem, int subclass, * characters first. If this function is not defined, the user will * receive an %EIO error. * - * @ioctl: ``int ()(struct tty_struct *tty, unsigned int cmd, + * Can sleep. + * + * @ioctl: [TTY] ``int ()(struct tty_struct *tty, unsigned int cmd, * unsigned long arg)`` * * This function is called when the user requests an ioctl which is not @@ -106,7 +120,7 @@ int ldsem_down_write_nested(struct ld_semaphore *sem, int subclass, * 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, + * @compat_ioctl: [TTY] ``int ()(struct tty_struct *tty, unsigned int cmd, * unsigned long arg)`` * * Process ioctl calls from 32-bit process on 64-bit system. @@ -116,27 +130,29 @@ int ldsem_down_write_nested(struct ld_semaphore *sem, int subclass, * 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)`` + * @set_termios: [TTY] ``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, + * @poll: [TTY] ``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)`` + * @hangup: [TTY] ``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. + * the tty driver. The driver should seek to perform this action quickly + * but should wait until any pending driver I/O is completed. No further + * calls into the ldisc code will occur. + * + * Can sleep. * - * @receive_buf: ``void ()(struct tty_struct *tty, const unsigned char *cp, - * const char *fp, int count)`` + * @receive_buf: [DRV] ``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 @@ -145,7 +161,7 @@ int ldsem_down_write_nested(struct ld_semaphore *sem, int subclass, * 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)`` + * @write_wakeup: [DRV] ``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 @@ -154,13 +170,13 @@ int ldsem_down_write_nested(struct ld_semaphore *sem, int subclass, * 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)`` + * @dcd_change: [DRV] ``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)`` + * @receive_buf2: [DRV] ``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 @@ -176,6 +192,9 @@ int ldsem_down_write_nested(struct ld_semaphore *sem, int subclass, * 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. + * + * Hooks marked [TTY] are invoked from the TTY core, the [DRV] ones from the + * tty_driver side. */ struct tty_ldisc_ops { char *name; |