mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-11-23 20:24:12 +08:00
Documentation: add TTY chapter
We now have all the kernel-doc comments in the code ready. So add a couple of documents dragging those into generated docs from Documentation/. There is only some sugar text around included kernel-docs here. It's a complete chapter, to be extended later as desired. This is a solid cornerstone for the time being, I believe. Signed-off-by: Jiri Slaby <jslaby@suse.cz> Link: https://lore.kernel.org/r/20211126081611.11001-24-jslaby@suse.cz Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jiri Slaby
Greg Kroah-Hartman
parent
31bc35d334
commit
3f19fed8d0
@ -137,6 +137,7 @@ needed).
|
||||
misc-devices/index
|
||||
scheduler/index
|
||||
mhi/index
|
||||
tty/index
|
||||
|
||||
Architecture-agnostic documentation
|
||||
-----------------------------------
|
||||
|
||||
63
Documentation/tty/index.rst
Normal file
63
Documentation/tty/index.rst
Normal file
@ -0,0 +1,63 @@
|
||||
.. SPDX-License-Identifier: GPL-2.0
|
||||
|
||||
===
|
||||
TTY
|
||||
===
|
||||
|
||||
Teletypewriter (TTY) layer takes care of all those serial devices. Including
|
||||
the virtual ones like pseudoterminal (PTY).
|
||||
|
||||
TTY structures
|
||||
==============
|
||||
|
||||
There are several major TTY structures. Every TTY device in a system has a
|
||||
corresponding struct tty_port. These devices are maintained by a TTY driver
|
||||
which is struct tty_driver. This structure describes the driver but also
|
||||
contains a reference to operations which could be performed on the TTYs. It is
|
||||
struct tty_operations. Then, upon open, a struct tty_struct is allocated and
|
||||
lives until the final close. During this time, several callbacks from struct
|
||||
tty_operations are invoked by the TTY layer.
|
||||
|
||||
Every character received by the kernel (both from devices and users) is passed
|
||||
through a preselected :doc:`tty_ldisc` (in
|
||||
short ldisc; in C, struct tty_ldisc_ops). Its task is to transform characters
|
||||
as defined by a particular ldisc or by user too. The default one is n_tty,
|
||||
implementing echoes, signal handling, jobs control, special characters
|
||||
processing, and more. The transformed characters are passed further to
|
||||
user/device, depending on the source.
|
||||
|
||||
In-detail description of the named TTY structures is in separate documents:
|
||||
|
||||
.. toctree::
|
||||
:maxdepth: 2
|
||||
|
||||
tty_driver
|
||||
tty_port
|
||||
tty_struct
|
||||
tty_ldisc
|
||||
tty_buffer
|
||||
n_tty
|
||||
tty_internals
|
||||
|
||||
Writing TTY Driver
|
||||
==================
|
||||
|
||||
Before one starts writing a TTY driver, they must consider
|
||||
:doc:`Serial <../driver-api/serial/driver>` and :doc:`USB Serial
|
||||
<../usb/usb-serial>` layers
|
||||
first. Drivers for serial devices can often use one of these specific layers to
|
||||
implement a serial driver. Only special devices should be handled directly by
|
||||
the TTY Layer. If you are about to write such a driver, read on.
|
||||
|
||||
A *typical* sequence a TTY driver performs is as follows:
|
||||
|
||||
#. Allocate and register a TTY driver (module init)
|
||||
#. Create and register TTY devices as they are probed (probe function)
|
||||
#. Handle TTY operations and events like interrupts (TTY core invokes the
|
||||
former, the device the latter)
|
||||
#. Remove devices as they are going away (remove function)
|
||||
#. Unregister and free the TTY driver (module exit)
|
||||
|
||||
Steps regarding driver, i.e. 1., 3., and 5. are described in detail in
|
||||
:doc:`tty_driver`. For the other two (devices handling), look into
|
||||
:doc:`tty_port`.
|
||||
22
Documentation/tty/n_tty.rst
Normal file
22
Documentation/tty/n_tty.rst
Normal file
@ -0,0 +1,22 @@
|
||||
.. SPDX-License-Identifier: GPL-2.0
|
||||
|
||||
=====
|
||||
N_TTY
|
||||
=====
|
||||
|
||||
.. contents:: :local:
|
||||
|
||||
The default (and fallback) :doc:`TTY line discipline <tty_ldisc>`. It tries to
|
||||
handle characters as per POSIX.
|
||||
|
||||
External Functions
|
||||
==================
|
||||
|
||||
.. kernel-doc:: drivers/tty/n_tty.c
|
||||
:export:
|
||||
|
||||
Internal Functions
|
||||
==================
|
||||
|
||||
.. kernel-doc:: drivers/tty/n_tty.c
|
||||
:internal:
|
||||
46
Documentation/tty/tty_buffer.rst
Normal file
46
Documentation/tty/tty_buffer.rst
Normal file
@ -0,0 +1,46 @@
|
||||
.. SPDX-License-Identifier: GPL-2.0
|
||||
|
||||
==========
|
||||
TTY Buffer
|
||||
==========
|
||||
|
||||
.. contents:: :local:
|
||||
|
||||
Here, we document functions for taking care of tty buffer and their flipping.
|
||||
Drivers are supposed to fill the buffer by one of those functions below and
|
||||
then flip the buffer, so that the data are passed to :doc:`line discipline
|
||||
<tty_ldisc>` for further processing.
|
||||
|
||||
Flip Buffer Management
|
||||
======================
|
||||
|
||||
.. kernel-doc:: drivers/tty/tty_buffer.c
|
||||
:identifiers: tty_prepare_flip_string tty_insert_flip_string_fixed_flag
|
||||
tty_insert_flip_string_flags __tty_insert_flip_char
|
||||
tty_flip_buffer_push tty_ldisc_receive_buf
|
||||
|
||||
----
|
||||
|
||||
Other Functions
|
||||
===============
|
||||
|
||||
.. kernel-doc:: drivers/tty/tty_buffer.c
|
||||
:identifiers: tty_buffer_space_avail tty_buffer_set_limit
|
||||
|
||||
----
|
||||
|
||||
Buffer Locking
|
||||
==============
|
||||
|
||||
These are used only in special circumstances. Avoid them.
|
||||
|
||||
.. kernel-doc:: drivers/tty/tty_buffer.c
|
||||
:identifiers: tty_buffer_lock_exclusive tty_buffer_unlock_exclusive
|
||||
|
||||
----
|
||||
|
||||
Internal Functions
|
||||
==================
|
||||
|
||||
.. kernel-doc:: drivers/tty/tty_buffer.c
|
||||
:internal:
|
||||
128
Documentation/tty/tty_driver.rst
Normal file
128
Documentation/tty/tty_driver.rst
Normal file
@ -0,0 +1,128 @@
|
||||
.. SPDX-License-Identifier: GPL-2.0
|
||||
|
||||
=============================
|
||||
TTY Driver and TTY Operations
|
||||
=============================
|
||||
|
||||
.. contents:: :local:
|
||||
|
||||
Allocation
|
||||
==========
|
||||
|
||||
The first thing a driver needs to do is to allocate a struct tty_driver. This
|
||||
is done by tty_alloc_driver() (or __tty_alloc_driver()). Next, the newly
|
||||
allocated structure is filled with information. See `TTY Driver Reference`_ at
|
||||
the end of this document on what actually shall be filled in.
|
||||
|
||||
The allocation routines expect a number of devices the driver can handle at
|
||||
most and flags. Flags are those starting ``TTY_DRIVER_`` listed and described
|
||||
in `TTY Driver Flags`_ below.
|
||||
|
||||
When the driver is about to be freed, tty_driver_kref_put() is called on that.
|
||||
It will decrements the reference count and if it reaches zero, the driver is
|
||||
freed.
|
||||
|
||||
For reference, both allocation and deallocation functions are explained here in
|
||||
detail:
|
||||
|
||||
.. kernel-doc:: drivers/tty/tty_io.c
|
||||
:identifiers: __tty_alloc_driver tty_driver_kref_put
|
||||
|
||||
TTY Driver Flags
|
||||
----------------
|
||||
|
||||
Here comes the documentation of flags accepted by tty_alloc_driver() (or
|
||||
__tty_alloc_driver()):
|
||||
|
||||
.. kernel-doc:: include/linux/tty_driver.h
|
||||
:doc: TTY Driver Flags
|
||||
|
||||
----
|
||||
|
||||
Registration
|
||||
============
|
||||
|
||||
When a struct tty_driver is allocated and filled in, it can be registered using
|
||||
tty_register_driver(). It is recommended to pass ``TTY_DRIVER_DYNAMIC_DEV`` in
|
||||
flags of tty_alloc_driver(). If it is not passed, *all* devices are also
|
||||
registered during tty_register_driver() and the following paragraph of
|
||||
registering devices can be skipped for such drivers. However, the struct
|
||||
tty_port part in `Registering Devices`_ is still relevant there.
|
||||
|
||||
.. kernel-doc:: drivers/tty/tty_io.c
|
||||
:identifiers: tty_register_driver tty_unregister_driver
|
||||
|
||||
Registering Devices
|
||||
-------------------
|
||||
|
||||
Every TTY device shall be backed by a struct tty_port. Usually, TTY drivers
|
||||
embed tty_port into device's private structures. Further details about handling
|
||||
tty_port can be found in :doc:`tty_port`. The driver is also recommended to use
|
||||
tty_port's reference counting by tty_port_get() and tty_port_put(). The final
|
||||
put is supposed to free the tty_port including the device's private struct.
|
||||
|
||||
Unless ``TTY_DRIVER_DYNAMIC_DEV`` was passed as flags to tty_alloc_driver(),
|
||||
TTY driver is supposed to register every device discovered in the system
|
||||
(the latter is preferred). This is performed by tty_register_device(). Or by
|
||||
tty_register_device_attr() if the driver wants to expose some information
|
||||
through struct attribute_group. Both of them register ``index``'th device and
|
||||
upon return, the device can be opened. There are also preferred tty_port
|
||||
variants described in `Linking Devices to Ports`_ later. It is up to driver to
|
||||
manage free indices and choosing the right one. The TTY layer only refuses to
|
||||
register more devices than passed to tty_alloc_driver().
|
||||
|
||||
When the device is opened, the TTY layer allocates struct tty_struct and starts
|
||||
calling operations from :c:member:`tty_driver.ops`, see `TTY Operations
|
||||
Reference`_.
|
||||
|
||||
The registration routines are documented as follows:
|
||||
|
||||
.. kernel-doc:: drivers/tty/tty_io.c
|
||||
:identifiers: tty_register_device tty_register_device_attr
|
||||
tty_unregister_device
|
||||
|
||||
----
|
||||
|
||||
Linking Devices to Ports
|
||||
------------------------
|
||||
As stated earlier, every TTY device shall have a struct tty_port assigned to
|
||||
it. It must be known to the TTY layer at :c:member:`tty_driver.ops.install()`
|
||||
at latest. There are few helpers to *link* the two. Ideally, the driver uses
|
||||
tty_port_register_device() or tty_port_register_device_attr() instead of
|
||||
tty_register_device() and tty_register_device_attr() at the registration time.
|
||||
This way, the driver needs not care about linking later on.
|
||||
|
||||
If that is not possible, the driver still can link the tty_port to a specific
|
||||
index *before* the actual registration by tty_port_link_device(). If it still
|
||||
does not fit, tty_port_install() can be used from the
|
||||
:c:member:`tty_driver.ops.install` hook as a last resort. The last one is
|
||||
dedicated mostly for in-memory devices like PTY where tty_ports are allocated
|
||||
on demand.
|
||||
|
||||
The linking routines are documented here:
|
||||
|
||||
.. kernel-doc:: drivers/tty/tty_port.c
|
||||
:identifiers: tty_port_link_device tty_port_register_device
|
||||
tty_port_register_device_attr
|
||||
|
||||
----
|
||||
|
||||
TTY Driver Reference
|
||||
====================
|
||||
|
||||
All members of struct tty_driver are documented here. The required members are
|
||||
noted at the end. struct tty_operations are documented next.
|
||||
|
||||
.. kernel-doc:: include/linux/tty_driver.h
|
||||
:identifiers: tty_driver
|
||||
|
||||
----
|
||||
|
||||
TTY Operations Reference
|
||||
========================
|
||||
|
||||
When a TTY is registered, these driver hooks can be invoked by the TTY layer:
|
||||
|
||||
.. kernel-doc:: include/linux/tty_driver.h
|
||||
:identifiers: tty_operations
|
||||
|
||||
31
Documentation/tty/tty_internals.rst
Normal file
31
Documentation/tty/tty_internals.rst
Normal file
@ -0,0 +1,31 @@
|
||||
.. SPDX-License-Identifier: GPL-2.0
|
||||
|
||||
=============
|
||||
TTY Internals
|
||||
=============
|
||||
|
||||
.. contents:: :local:
|
||||
|
||||
Kopen
|
||||
=====
|
||||
|
||||
These functions serve for opening a TTY from the kernelspace:
|
||||
|
||||
.. kernel-doc:: drivers/tty/tty_io.c
|
||||
:identifiers: tty_kopen_exclusive tty_kopen_shared tty_kclose
|
||||
|
||||
----
|
||||
|
||||
Exported Internal Functions
|
||||
===========================
|
||||
|
||||
.. kernel-doc:: drivers/tty/tty_io.c
|
||||
:identifiers: tty_release_struct tty_dev_name_to_number tty_get_icount
|
||||
|
||||
----
|
||||
|
||||
Internal Functions
|
||||
==================
|
||||
|
||||
.. kernel-doc:: drivers/tty/tty_io.c
|
||||
:internal:
|
||||
@ -6,6 +6,12 @@ TTY Line Discipline
|
||||
|
||||
.. contents:: :local:
|
||||
|
||||
TTY line discipline process all incoming and outgoing character from/to a tty
|
||||
device. The default line discipline is :doc:`N_TTY <n_tty>`. It is also a
|
||||
fallback if establishing any other discipline for a tty fails. If even N_TTY
|
||||
fails, N_NULL takes over. That never fails, but also does not process any
|
||||
characters -- it throws them away.
|
||||
|
||||
Registration
|
||||
============
|
||||
|
||||
|
||||
70
Documentation/tty/tty_port.rst
Normal file
70
Documentation/tty/tty_port.rst
Normal file
@ -0,0 +1,70 @@
|
||||
.. SPDX-License-Identifier: GPL-2.0
|
||||
|
||||
========
|
||||
TTY Port
|
||||
========
|
||||
|
||||
.. contents:: :local:
|
||||
|
||||
The TTY drivers are advised to use struct tty_port helpers as much as possible.
|
||||
If the drivers implement :c:member:`tty_port.ops.activate()` and
|
||||
:c:member:`tty_port.ops.shutdown()`, they can use tty_port_open(),
|
||||
tty_port_close(), and tty_port_hangup() in respective
|
||||
:c:member:`tty_struct.ops` hooks.
|
||||
|
||||
The reference and details are contained in the `TTY Port Reference`_ and `TTY
|
||||
Port Operations Reference`_ sections at the bottom.
|
||||
|
||||
TTY Port Functions
|
||||
==================
|
||||
|
||||
Init & Destroy
|
||||
--------------
|
||||
|
||||
.. kernel-doc:: drivers/tty/tty_port.c
|
||||
:identifiers: tty_port_init tty_port_destroy
|
||||
tty_port_get tty_port_put
|
||||
|
||||
Open/Close/Hangup Helpers
|
||||
-------------------------
|
||||
|
||||
.. kernel-doc:: drivers/tty/tty_port.c
|
||||
:identifiers: tty_port_install tty_port_open tty_port_block_til_ready
|
||||
tty_port_close tty_port_close_start tty_port_close_end tty_port_hangup
|
||||
tty_port_shutdown
|
||||
|
||||
TTY Refcounting
|
||||
---------------
|
||||
|
||||
.. kernel-doc:: drivers/tty/tty_port.c
|
||||
:identifiers: tty_port_tty_get tty_port_tty_set
|
||||
|
||||
TTY Helpers
|
||||
-----------
|
||||
|
||||
.. kernel-doc:: drivers/tty/tty_port.c
|
||||
:identifiers: tty_port_tty_hangup tty_port_tty_wakeup
|
||||
|
||||
|
||||
Modem Signals
|
||||
-------------
|
||||
|
||||
.. kernel-doc:: drivers/tty/tty_port.c
|
||||
:identifiers: tty_port_carrier_raised tty_port_raise_dtr_rts
|
||||
tty_port_lower_dtr_rts
|
||||
|
||||
----
|
||||
|
||||
TTY Port Reference
|
||||
==================
|
||||
|
||||
.. kernel-doc:: include/linux/tty_port.h
|
||||
:identifiers: tty_port
|
||||
|
||||
----
|
||||
|
||||
TTY Port Operations Reference
|
||||
=============================
|
||||
|
||||
.. kernel-doc:: include/linux/tty_port.h
|
||||
:identifiers: tty_port_operations
|
||||
81
Documentation/tty/tty_struct.rst
Normal file
81
Documentation/tty/tty_struct.rst
Normal file
@ -0,0 +1,81 @@
|
||||
.. SPDX-License-Identifier: GPL-2.0
|
||||
|
||||
==========
|
||||
TTY Struct
|
||||
==========
|
||||
|
||||
.. contents:: :local:
|
||||
|
||||
struct tty_struct is allocated by the TTY layer upon the first open of the TTY
|
||||
device and released after the last close. The TTY layer passes this structure
|
||||
to most of struct tty_operation's hooks. Members of tty_struct are documented
|
||||
in `TTY Struct Reference`_ at the bottom.
|
||||
|
||||
Initialization
|
||||
==============
|
||||
|
||||
.. kernel-doc:: drivers/tty/tty_io.c
|
||||
:identifiers: tty_init_termios
|
||||
|
||||
Name
|
||||
====
|
||||
|
||||
.. kernel-doc:: drivers/tty/tty_io.c
|
||||
:identifiers: tty_name
|
||||
|
||||
Reference counting
|
||||
==================
|
||||
|
||||
.. kernel-doc:: include/linux/tty.h
|
||||
:identifiers: tty_kref_get
|
||||
|
||||
.. kernel-doc:: drivers/tty/tty_io.c
|
||||
:identifiers: tty_kref_put
|
||||
|
||||
Install
|
||||
=======
|
||||
|
||||
.. kernel-doc:: drivers/tty/tty_io.c
|
||||
:identifiers: tty_standard_install
|
||||
|
||||
Read & Write
|
||||
============
|
||||
|
||||
.. kernel-doc:: drivers/tty/tty_io.c
|
||||
:identifiers: tty_put_char
|
||||
|
||||
Start & Stop
|
||||
============
|
||||
|
||||
.. kernel-doc:: drivers/tty/tty_io.c
|
||||
:identifiers: start_tty stop_tty
|
||||
|
||||
Wakeup
|
||||
======
|
||||
|
||||
.. kernel-doc:: drivers/tty/tty_io.c
|
||||
:identifiers: tty_wakeup
|
||||
|
||||
Hangup
|
||||
======
|
||||
|
||||
.. kernel-doc:: drivers/tty/tty_io.c
|
||||
:identifiers: tty_hangup tty_vhangup tty_hung_up_p
|
||||
|
||||
Misc
|
||||
====
|
||||
|
||||
.. kernel-doc:: drivers/tty/tty_io.c
|
||||
:identifiers: tty_do_resize
|
||||
|
||||
TTY Struct Flags
|
||||
================
|
||||
|
||||
.. kernel-doc:: include/linux/tty.h
|
||||
:doc: TTY Struct Flags
|
||||
|
||||
TTY Struct Reference
|
||||
====================
|
||||
|
||||
.. kernel-doc:: include/linux/tty.h
|
||||
:identifiers: tty_struct
|
||||
Loading…
Reference in New Issue
Block a user