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| author | Sang-Heon Jeon <ekffu200098@gmail.com> | 2026-08-24 01:18:14 +0900 |
|---|---|---|
| committer | Julia Lawall <Julia.Lawall@inria.fr> | 2026-08-23 22:12:11 +0200 |
| commit | 2bd30b8dc75b823dd7bbef9d7bc68e1fd7ecee5c (patch) | |
| tree | dcc4da1d99f17541c5590ac63c77da4bf372a4ab /Documentation/driver-api/tty/index.rst | |
| download | linux-stable-2bd30b8dc75b823dd7bbef9d7bc68e1fd7ecee5c.tar.gz linux-stable-2bd30b8dc75b823dd7bbef9d7bc68e1fd7ecee5c.zip | |
coccinelle: alloc_cast: drop removed allocatorsgrafted
- pci_alloc_consistent() and pci_zalloc_consistent() were removed by
commit 7968778914e5
("PCI: Remove the deprecated "pci-dma-compat.h" API")
- kmem_alloc() was removed by commit f078d4ea8276
("xfs: convert kmem_alloc() to kmalloc()")
- kmem_zalloc() was removed by commit 10634530f7ba
("xfs: convert kmem_zalloc() to kzalloc()")
- kmem_zone_alloc() and kmem_zone_zalloc() were removed by commit
bae633a4a283 ("xfs: remove xfs_zone_{alloc,zalloc} helpers")
So drop them from the rules.
No functional change.
Signed-off-by: Sang-Heon Jeon <ekffu200098@gmail.com>
Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
Diffstat (limited to 'Documentation/driver-api/tty/index.rst')
| -rw-r--r-- | Documentation/driver-api/tty/index.rst | 75 |
1 files changed, 75 insertions, 0 deletions
diff --git a/Documentation/driver-api/tty/index.rst b/Documentation/driver-api/tty/index.rst new file mode 100644 index 000000000..c1ffe3d1e --- /dev/null +++ b/Documentation/driver-api/tty/index.rst @@ -0,0 +1,75 @@ +.. 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 + tty_ioctl + tty_internals + console + +Writing TTY Driver +================== + +Before one starts writing a TTY driver, they must consider +:doc:`Serial <../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`. + +Other Documentation +=================== + +Miscellaneous documentation can be further found in these documents: + +.. toctree:: + :maxdepth: 2 + + moxa-smartio + n_gsm + n_tty |
